Catalog Resistors and Capacitors Electrolytic capacitors Transistor & diode packages Integrated circuit SMD packages Ball Grid Array Small Outline Packages Flat Packages     Surface Mount Technology (SMT) is a technique for mounting electrical components directly to the surface of a printed circuit board (PCB). The component that is mounted on the surface of the PCB using surface mount technology is called Surface Mount Device (SMD). SMT has essentially replaced the through-hole PCB manufacturing technology to reduce cost, and increase efficiency and productivity. Since the size of SMD components is very small, compared to through-hole components many more SMD components can be arranged in a given place. Selecting and knowing the right SMD component for your PCB is very necessary. SMD components have standard codes and sizes which as a PCB designer one should know. Kynix offers all sorts of SMD components for PCB manufacturing which can be found here. This article will help you choose the right SMD component from the Kynix library.   SMD components come in various packages and sizes to facilitate the automated manufacturing of PCBs. Most of the SMD components are standardized to make manufacturing easy. The most commonly used SMD components are capacitors and resistors. The standards of these components are set by Joint Electron Device Engineering Council.   There are different types of packages. When a new package is introduced in the industry, it is named after its initials such as Quad Flat Package (QFP). While some packages have no name, it creates confusion in the industry. Below we have discussed flat chip SMD resistors, capacitors, diodes & transistors, and IC packages. The size of the SMD chip for resistor, capacitors, and some of the diodes is given by a 4 digits code, which represents the dimension of the flat chip either in inches or in millimeters. In the US it is represented in inches while outside the US it is represented in mm. The first two digits represent the length (L) of the component while the last two digits represent the width (W) of the component. While the thickness is also an important factor in manufacturing, it is not mentioned in the 4 digits code, for this, the actual datasheet of the component provided by the manufacturer should be used.   Many PCB components such as resistors, capacitors, diodes, FETs, and other transistors are available in SMD. SMD resistors and capacitors, also known as passive devices, come in different sizes. Depending upon the availability of space, soldering capability, and environment temperature, different packages can be used. The names of these packages given in the table below are derived from the size of the components in inches.   Resistors and Capacitors Below are the most common size codes for capacitors and resistors. You can find these resistors and capacitors here.   S. NoPackageDimensions (in)12010.02x0.01220160.2x0.1632020.02x0.0242040.02x0.0452070.02x0.0763030.03x0.0373060.03x0.0684020.04x0.0294040.04x0.04104060.04x0.02115020.05x0.05125050.05x0.08135080.05x0.1145100.05x0.1156030.06x0.03166060.06x0.06176120.06x12187050.07x0.05198050.08x0.05208080.08x0.08218150.08x0.15228160.08x0.16238300.08x0.32410100.1x0.12510200.1x0.22610500.1x0.52712060.12x0.062812100.12x0.12912160.12x0.163012180.12x0.183112200.12x0.23212240.12x0.243312250.12x0.253414050.14x0.053515050.15x0.053615060.15x0.063715100.15x0.13815750.15x0.753916080.16x0.084016320.16x0.324118120.18x0.124220100.2x0.14320120.2x0.124420180.2x0.184520300.2x0.34622080.22x0.084724090.24x0.094824120.24x0.124925100.25x0.15025120.25x0.125125150.25x0.155226150.26x0.155327250.27x0.255427260.27x0.265527280.27x0.285628160.28x0.165728170.28x0.175828180.28x0.185930140.3x0.146030200.3x0.2   At present most manufacturers can manufacture PCBs with SMD components up to 0603 easily, going below this size to such as 0402 or 0201 is still difficult for the manufacturers, and thus the cost of manufacturing increases if these components are included in the design. Therefore, most of the manufacturers recommend using 0603 components for PCB design.   Electrolytic capacitors The electronic industry adopted EIA and IECQ standards for molded tantalum capacitors. These packages are named A, B, C, D, and E. These correspond to different sizes in millimeters.   Package height is not included in the size code.   EIA codeMetric codeDimensionA32163.2 x1.6 mmB35283.5 x 2.8 mmC60326.0 x 3.2 mmD73437.3 x 4.3 mm   Several other electronic devices can not follow any standard because of their unique nature. SMD components like an inductor, transformers, crystals, resonators, and temperature-controlled oscillators require different packages often larger than the standard packages. It is very unlikely that these packages will be standardized because of their unique nature. However, the package must be chosen in a way to make pick and place possible. These capacitors can be found here.   Transistor & diode packages SMD transistors and diodes have the same package type. Transistors have three pins while a diode has two pins. The third pin is added to the diode package to keep the orientation right. Diodes are packages that come in different varieties. Some packages follow the standards of capacitors and resistors that we discussed above.   Some of the most common diode and transistor packages are SOT-23 - Small Outline Transistor: It is the most common diode and transistor package. It has three pins and measures 3 mm x 1.75 mm x 1.3 mm. It is used for low-power applications.SOT-223 - Small Outline Transistor: This diode package is used for high-power applications. It is bigger than SOT-23. It measures 6.7 mm x 3.7 mm x1.8 mm. It has four pins with which the fourth one is used for heat dissipation. Integrated circuit SMD packages IC packages are found in many packages and can be classified in many different ways. It is very common to hear the terms DIP, SOP, SIP, TSOP, QSOP, MSOP, SOIC, QFP etc. These are the different packages of IC. They can be categorized as.   There are three main package types for surface mount integrated circuits: Ball grid array (BGA)Small outline package (SOP)Quad flat pack (QFP) Ball Grid Array   Ball Grid Array package has solder balls attached to the underside of the package. Beneath the balls are electrical traces of IC. Ball Grid Array has further the following types. Molded Array Process Ball Grid Array (MAPBGA)Plastic Ball Grid Array (PBGA)  Thermally Enhanced Plastic Ball Grid Array (TEPBGA)Tape Ball Grid Array (TBGA)Package on Package   MicroBGA. Small Outline Packages   Small Outline Package is another IC package in which pins come out from the sides of the IC. The convention used for SOIC or SO package is the name followed by the number of pins used in the package. i.e SO-12 means the IC has 12 pins.   Further types of SOP/SOIC are SOJ - Small Out-Line J-Leaded PackageTSOP -Thin Small Outline PackageVSOP -Very Small Outline Package).TSSOP -Thin Shrink Small Outline Package SSOP -Shrink Small Outline PackageQSOP -Quarter-size Small Outline Package Flat Packages   Flat IC package have pins arranged on its side in L or J shape. These pins are arranged on the side of the package with the leads coming out. This package further has many subtypes. QFP (Quad Flat Package)TQFP (Thin Quad Flat Package)STQFP (Small Thin Quad Plastic Flat Package)FQFP (Fine-pitch Quad Flat Package),(Low profile Quad Flat Package)VQFP (Very-small Quad Flat Package)ETQFP (Exposed thin quad Flat Package)PQFN (Power Quad Flat Package)PQFP (Plastic Quad Flat Package)QFJ (Quad Flat J-Leaded Package)QFN (Quad Flat Non-Leaded Package)

Keypads are input devices that are being widely used in many embedded system projects. It can be found in appliances, door locks, and industrial machines. Keypads are used to take input from the user in the form of numbers or characters which can further be used for processing such as password, menu selection and navigating among different options. One of the most common and low-cost keypads is the matrix keypad with 4×4 or 3×3 buttons. In this article we will discuss how a low cost 4×4 matrix keypad can be used in STM32. Before proceeding further, we will need to know few things.Materials14×4 matrix keypad2STM32 F401How a 4×4 keypad works? 4×4 keypadIn microcontrollers usually a pin is used to take input from the user. This input can be either 1 or 0. Multiple 1’s and 0’s can be combined to store more information. For this purpose, multiple input pins will be required. However, this becomes impractical when the input pins required exceed certain number such as 16 or 9 as the microcontrollers do not have this many pins available.The 4×4 matrix keypad solves this problem and reduced the required number of pins to 8 or 6. It  is made of a thin and flexible membrane. The 16 keys of the 4 x 4 keypad module are arranged in a matrix of rows and columns. A copper trace connects each of these switches to the others. The rows and column are not connected to each other in normal condition. When we push a key, a column and a row come into contact with each other. In matrix keypads the buttons are divided among rows and columns. Four buttons lie on each row and each column. Thus, columns are connected to external input pins of microcontroller while the rows are connected to output pins of microcontroller. The output pins are high all the time. When a button is pressed the corresponding column goes high and the microcontroller detects it. Finding which column has been activated is easy as each column is connected to a separate pin, however, finding a row is difficult. Once both row and column are identified then the corresponding button can be identified. A clever method to identify the pressed key is to switch off all output pins except one, and then check which input pins is high. Doing this for all the output pins will identify the row. Once the row number is found out, the button can easily be traced out.matrix keypad in STM32STM32 F401 implementationSTM32 F401In CubeMX the relative microcontroller of our choice is selected which in our case is STM32 F401CDU6. The GPIOs that need to be selected as output or external interrupt input are given in the figure above. In the NVIC tab the interrupt should be enabled. Other necessary settings are given below.RCC → Crystal/Ceramic ResonatorSYS → Debug → Serial WireClock Configuration → HCLK → 84 MHzClock Configuration → PLL Source Mux → HSE Once the CubeMX code is generated the following code should be added to the /* USER CODE BEGIN PV */ section./* USER CODE BEGIN PV */  GPIO_InitTypeDef GPIO_InitStructPrivate = {0};  uint32_t previousM = 0;  uint32_t currentM = 0;  uint8_t key = 0;  uint8_t InputData[5] = {0};  int i = 0;/* USER CODE END PV */This code section defines the necessary variables that will come handy later.In the main.c section in /* USER CODE BEGIN 2 */ the output configured pins should be set to 1.  /* USER CODE BEGIN 2 */  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_15, 1);  HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, 1);  HAL_GPIO_WritePin(GPIOB, GPIO_PIN_4, 1);  HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5, 1);  /* USER CODE END 2 */  While the interrupt callback function void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin) should be added to /* USER CODE BEGIN 4 */ section.void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin){  currentM = HAL_GetTick();  if (currentM - previousM > 10) {    /*Configure GPIO pins : PB6 PB7 PB8 PB9 to GPIO_INPUT*/    GPIO_InitStructPrivate.Pin = GPIO_PIN_6|GPIO_PIN_7|GPIO_PIN_8|GPIO_PIN_9;    GPIO_InitStructPrivate.Mode = GPIO_MODE_INPUT;    GPIO_InitStructPrivate.Pull = GPIO_NOPULL;    GPIO_InitStructPrivate.Speed = GPIO_SPEED_FREQ_LOW;    HAL_GPIO_Init(GPIOB, &GPIO_InitStructPrivate);     HAL_GPIO_WritePin(GPIOA, GPIO_PIN_15, 1);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_4, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5, 0);    if(GPIO_Pin == GPIO_PIN_6 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_6))    {      key = 68; //ASCII value of D    }    else if(GPIO_Pin == GPIO_PIN_7 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_7))    {      key = 67; //ASCII value of C    }    else if(GPIO_Pin == GPIO_PIN_8 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_8))    {      key = 66; //ASCII value of B    }    else if(GPIO_Pin == GPIO_PIN_9 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_9))    {      key = 65; //ASCII value of A    }     HAL_GPIO_WritePin(GPIOA, GPIO_PIN_15, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, 1);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_4, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5, 0);    if(GPIO_Pin == GPIO_PIN_6 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_6))    {      key = 35; //ASCII value of #    }    else if(GPIO_Pin == GPIO_PIN_7 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_7))    {      key = 57; //ASCII value of 9      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 9;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }    else if(GPIO_Pin == GPIO_PIN_8 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_8))    {      key = 54; //ASCII value of 6      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 6;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }    else if(GPIO_Pin == GPIO_PIN_9 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_9))    {      key = 51; //ASCII value of 3      if (i == 4)            {             //Send Data            }            else            {             InputData[i] = 3;            }            if(i <= 4)            {             i = i + 1;             }            else            {             i = 0;            }    }     HAL_GPIO_WritePin(GPIOA, GPIO_PIN_15, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_4, 1);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5, 0);    if(GPIO_Pin == GPIO_PIN_6 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_6))    {      key = 48; //ASCII value of 0      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 0;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }    else if(GPIO_Pin == GPIO_PIN_7 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_7))    {      key = 56; //ASCII value of 8      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 8;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }    else if(GPIO_Pin == GPIO_PIN_8 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_8))    {      key = 53; //ASCII value of 5      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 5;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }    else if(GPIO_Pin == GPIO_PIN_9 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_9))    {      key = 50; //ASCII value of 2      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 2;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }     HAL_GPIO_WritePin(GPIOA, GPIO_PIN_15, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_4, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5, 1);    if(GPIO_Pin == GPIO_PIN_6 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_6))    {      key = 42; //ASCII value of *     }    else if(GPIO_Pin == GPIO_PIN_7 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_7))    {      key = 55; //ASCII value of 7      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 7;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }    else if(GPIO_Pin == GPIO_PIN_8 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_8))    {      key = 52; //ASCII value of 4      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 4;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }    else if(GPIO_Pin == GPIO_PIN_9 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_9))    {      key = 49; //ASCII value of 1      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 1;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }     HAL_GPIO_WritePin(GPIOA, GPIO_PIN_15, 1);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, 1);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_4, 1);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5, 1);    /*Configure GPIO pins : PB6 PB7 PB8 PB9 back to EXTI*/    GPIO_InitStructPrivate.Mode = GPIO_MODE_IT_RISING;    GPIO_InitStructPrivate.Pull = GPIO_PULLDOWN;    HAL_GPIO_Init(GPIOB, &GPIO_InitStructPrivate);    previousM = currentM;   }} In the callback function the two linescurrentM = HAL_GetTick();  if (currentM - previousM > 10)takes care of the debouncing of the buttons. In keypad it is a common problem that a but hits once is recorded twice or thrice. So, take of that, a little delay is added at the beginning of callback function.The complete code is given below.#include "main.h" /* USER CODE BEGIN PV */  GPIO_InitTypeDef GPIO_InitStructPrivate = {0};  uint32_t previousM = 0;  uint32_t currentM = 0;  uint8_t key = 0;  uint8_t InputData[5] = {0};  int i = 0;/* USER CODE END PV */ /* Private function prototypes -----------------------------------------------*/void SystemClock_Config(void);static void MX_GPIO_Init(void);/* USER CODE BEGIN PFP */ /* USER CODE END PFP */ /* Private user code ---------------------------------------------------------*//* USER CODE BEGIN 0 */ /* USER CODE END 0 */ /**  * @brief  The application entry point.  * @retval int  */int main(void){  /* USER CODE BEGIN 1 */   /* USER CODE END 1 */   /* MCU Configuration--------------------------------------------------------*/   /* Reset of all peripherals, Initializes the Flash interface and the Systick. */  HAL_Init();   /* USER CODE BEGIN Init */   /* USER CODE END Init */   /* Configure the system clock */  SystemClock_Config();   /* USER CODE BEGIN SysInit */   /* USER CODE END SysInit */   /* Initialize all configured peripherals */  MX_GPIO_Init();  /* USER CODE BEGIN 2 */  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_15, 1);  HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, 1);  HAL_GPIO_WritePin(GPIOB, GPIO_PIN_4, 1);  HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5, 1);  /* USER CODE END 2 */   /* Infinite loop */  /* USER CODE BEGIN WHILE */  while (1)  {    /* USER CODE END WHILE */     /* USER CODE BEGIN 3 */  }  /* USER CODE END 3 */}  /* USER CODE BEGIN 4 */void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin){  currentM = HAL_GetTick();  if (currentM - previousM > 10) {    /*Configure GPIO pins : PB6 PB7 PB8 PB9 to GPIO_INPUT*/    GPIO_InitStructPrivate.Pin = GPIO_PIN_6|GPIO_PIN_7|GPIO_PIN_8|GPIO_PIN_9;    GPIO_InitStructPrivate.Mode = GPIO_MODE_INPUT;    GPIO_InitStructPrivate.Pull = GPIO_NOPULL;    GPIO_InitStructPrivate.Speed = GPIO_SPEED_FREQ_LOW;    HAL_GPIO_Init(GPIOB, &GPIO_InitStructPrivate);     HAL_GPIO_WritePin(GPIOA, GPIO_PIN_15, 1);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_4, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5, 0);    if(GPIO_Pin == GPIO_PIN_6 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_6))    {      key = 68; //ASCII value of D    }    else if(GPIO_Pin == GPIO_PIN_7 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_7))    {      key = 67; //ASCII value of C    }    else if(GPIO_Pin == GPIO_PIN_8 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_8))    {      key = 66; //ASCII value of B    }    else if(GPIO_Pin == GPIO_PIN_9 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_9))    {      key = 65; //ASCII value of A    }     HAL_GPIO_WritePin(GPIOA, GPIO_PIN_15, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, 1);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_4, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5, 0);    if(GPIO_Pin == GPIO_PIN_6 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_6))    {      key = 35; //ASCII value of #    }    else if(GPIO_Pin == GPIO_PIN_7 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_7))    {      key = 57; //ASCII value of 9      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 9;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }    else if(GPIO_Pin == GPIO_PIN_8 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_8))    {      key = 54; //ASCII value of 6      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 6;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }    else if(GPIO_Pin == GPIO_PIN_9 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_9))    {      key = 51; //ASCII value of 3      if (i == 4)            {             //Send Data            }            else            {             InputData[i] = 3;            }            if(i <= 4)            {             i = i + 1;             }            else            {             i = 0;            }    }     HAL_GPIO_WritePin(GPIOA, GPIO_PIN_15, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_4, 1);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5, 0);    if(GPIO_Pin == GPIO_PIN_6 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_6))    {      key = 48; //ASCII value of 0      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 0;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }    else if(GPIO_Pin == GPIO_PIN_7 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_7))    {      key = 56; //ASCII value of 8      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 8;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }    else if(GPIO_Pin == GPIO_PIN_8 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_8))    {      key = 53; //ASCII value of 5      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 5;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }    else if(GPIO_Pin == GPIO_PIN_9 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_9))    {      key = 50; //ASCII value of 2      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 2;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }     HAL_GPIO_WritePin(GPIOA, GPIO_PIN_15, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_4, 0);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5, 1);    if(GPIO_Pin == GPIO_PIN_6 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_6))    {      key = 42; //ASCII value of *     }    else if(GPIO_Pin == GPIO_PIN_7 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_7))    {      key = 55; //ASCII value of 7      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 7;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }    else if(GPIO_Pin == GPIO_PIN_8 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_8))    {      key = 52; //ASCII value of 4      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 4;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }    else if(GPIO_Pin == GPIO_PIN_9 && HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_9))    {      key = 49; //ASCII value of 1      if (i == 4)      {       //Send Data      }      else      {       InputData[i] = 1;      }      if(i <= 4)      {       i = i + 1;       }      else      {       i = 0;      }    }     HAL_GPIO_WritePin(GPIOA, GPIO_PIN_15, 1);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, 1);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_4, 1);    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5, 1);    /*Configure GPIO pins : PB6 PB7 PB8 PB9 back to EXTI*/    GPIO_InitStructPrivate.Mode = GPIO_MODE_IT_RISING;    GPIO_InitStructPrivate.Pull = GPIO_PULLDOWN;    HAL_GPIO_Init(GPIOB, &GPIO_InitStructPrivate);    previousM = currentM;   }}  

Introduction In most robots, electricity is used for command, control, and at least one stage of actuation. Electronics are used to transport all of this electricity. Robot baby is a new high-tech bionic robot created by American researchers. There is a huge selection of pre-manufactured, standard commodity components available. Discrete components such as resistors, capacitors, and transistors; small-scale integrated circuits such as op-amps, timing chips, and motor controllers; and large-scale integrated circuits such as memory chips, digital RF receivers, and full-fledged microprocessors with billions of transistors on a chip are examples of these. Even entire computer systems are sometimes viewed as modular components. As a result, many different types of robots, including robot babies, were invented. Catalog Introduction I What is the Robot Baby? II The Robot Baby Related Video III Common Sensors Used in Robots  IV Composition Structure  V The Differences between General Robot and Robot Baby 5.1 General Robot 5.2 Robot Baby VI The Convenience of Baby Simulator VII The Development Goals of Robot Baby Ⅷ The Influence of Robot Baby Ⅸ FAQ   I What is the Robot Baby? Robot baby is a new high-tech bionic robot created by American researchers. It is named "Diego SAN" after a one-year-old baby. It was created by Hanson robotics professionals for the Machine Perception Laboratory at the University of California, San Diego 's Institute for Neural Computing. The robot baby includes a high-resolution camera that can detect people's facial emotions. It, like a genuine infant, can make a range of facial expressions, such as smiles, mugs, and frowns. He even bites his lower lip like a child and tears well up in his eyes. Just by looking at the faces, it's difficult to distinguish the difference between this synthetic child and the actual thing. For example, joy, sadness, terror, and perplexity. It will not vomit food or wet clothes like a real baby, but the robot baby is clever enough to exhibit true infant facial expressions. II The Robot Baby Related Video Video: Engaged Couples Raise Robot Babies Robot Baby Description: Reality Works for providing the RealCare Baby Simulators and support. You will know how to take care of the real baby by the robot baby. III Common Sensors Used in Robots  Robotic sensors are used to estimate the status and environment of a robot. Sensors enable robots to comprehend and quantify the geometric and physical qualities of objects in their surroundings, such as location, orientation, velocity, acceleration, distance, size, force, moment, temperature, brightness, weight, and so on. 1 Light Sensor detect light and generate a difference in voltage. 2 Temperature Sensor Detect the surrounding temperature change. 3 proximity Sensor Create a technique for the robot to avoid collisions 4 Navigation and Positioning Sensors Approximate the position of a robot. 5 Sound Sensor A microphone that detects and returns the equivalent voltage of sound. 6 Tactile Sensor A device specifying an object’s contact. 7 Acceleration Sensor A gadget used to measure acceleration and tilt Figure1  Common Sensors Used in Robots IV Composition Structure Human beings are composed of five key components at the most fundamental level: A bodily structure;A muscle system for moving the body structure; and a sensory system for receiving information about the body and its surroundings.A source of power to stimulate the muscles and sensors;A brain system that interprets sensory data and instructs the muscles on what to perform. Furthermore, while humans have intangible qualities such as intelligence and morality, the list above pretty much covers it on a physical level. The configuration of the robot infant is odder. V The Differences between General Robot and Robot Baby 5.1 General Robot The great majority of robots do share some characteristics. To begin with,  almost all robots have a moving body. Some contain merely powered wheels, while others include dozens of movable parts composed of metal or plastic. Individual segments, like bones in your body, are joined together by joints. Figure 2  Fujitsu's HOAP-1 robot PHOTO COURTESY FUJITSU AND K&D TECHNOLOGY, INC. Robots use actuators to spin wheels and pivot jointed components. As actuators, some robots employ electric motors and solenoids, while others use a hydraulic system or a pneumatic system (a system driven by compressed gases). Robots can use any of these actuator types. All of the actuators are connected to an electrical circuit. The circuit provides direct power to electrical motors and solenoids, as well as activating the hydraulic system through the use of electrical valves. The course of the pressured fluid through the machine is determined by the valves. To move a hydraulic leg, for example, the controller of the robot would open the valve connecting the fluid pump to a piston cylinder attached to that leg. The compressed fluid would cause the piston to extend, causing the leg to swivel forward. To move their segments in two directions, robots often use pistons that can push in both directions. Figure 3  NASA's Urbie climbing stairs PHOTO COURTESY NASA JPL Everything connected to the circuit is controlled by the robot's computer. To move the robot, the computer activates all of the necessary motors and valves. Most robots can be reprogrammed, which means that you can change the robot's behavior by simply writing a new program to its computer. A typical design incorporates slotted wheels that are attached to the joints of the robot. A light beam is transmitted through the slots by an LED on one side of the wheel to a light sensor on the other side. When the robot moves a specific joint, the slotted wheel rotates. The light beam is disrupted as the wheel turns. The light sensor detects the flashing light pattern and transmits it to the computer. Based on this pattern, the computer can determine how far the joint has swiveled. The same basic mechanism is employed in computer mice. 5.2 Robot Baby Unlike ordinary robots, robot babies are enhanced in a variety of ways. They not only have the same appearance as real babies, but they can also select the skin tone of other countries. Facial expressions play a vital role in how babies connect with the outside world, assisting them in developing relationships with others. The robot infant is an improvement above previous versions of the technology, which completely reassembles its jaw. figure 4  “Diego San”- a baby robot  confused (left),happy (middle) and crying (right) Hanson Diego-san was created in 2013 by the robotics businesses Hanson Robotics and Kokoro for UCSD. Experts are now using Diego to find out how babies get their mothers to smile at them so regularly. When the Hungarian-American mathematician John von Neumann proposed the concept of an autonomous robot capable of recreating itself using raw materials. Today, Neumann's vision is becoming a reality, with one notable exception: the self-replicating robot is not made of aluminum, plastics, spur gears, or sprockets. The parent robot and its offspring, a new lineage of organisms known as Xenobots, are totally biological. "It was fascinating to find that we could [create] this Von Neumann machine, but utilizing cells instead of robot parts," says co-author Sam Kriegm of Harvard and co-author of the Xenobots research published today in PNAS. Scientists construct the first 'living' devices that can reproduce. A Computer scientist at the Wyss Institute for Biologically Inspired Engineering "People have philosophized about this for a long time," says Joshua Bongard, senior author and computer scientist at the University of Vermont. "However, you may now conduct experiments to develop biological machines or machines that create biology, which in turn creates machines." It's acceptable to be perplexed. Xenobots are referred to as "machines"  despite the fact that they lack any mechanical components. Science may be evolving faster than our paradigm for discussing and even imagining this new category of machine life. "I think it challenges us to recognize that there may not be a clear dividing line between machine and organism," Bongard adds. VI.  The Convenience of Baby Simulator RealCare Baby® 3 (formerly known as Baby Think It Over® or BTIO®) is the most advanced baby simulator on the market. What does RealCare Baby mean to the educators who use this learning aid in their classrooms? We asked teachers from across the country what RealCare Baby means to them. Watch this video to hear what they told us, and why they value RealCare Baby as a training tool and learning aid for life and career skills. What RealCare Baby Means to Educators The baby simulator successfully depicts how time-consuming and hard parenthood can be. These lifelike, newborn-size manikins are ideal for usage with teenagers since they have a number of program settings that imitate an infant's fluctuating requirements and require fast response. The unexpected nature of the programmed activities demonstrates that a baby's demands do not follow a defined schedule, but are easily monitored by the facilitator. Any prenatal education program will benefit from the baby simulator. Wriggling, squirming, Moro reflex-induced jump... Look no further than this automaton for proof that artificial intelligence is thriving. Cries, coos, and burp;Abuse of records, panic, and tampering;The regular control box comes with one pair of user keys and one set of teacher keys, as well as user response sheets, a teacher correction template, a diaper, a 9V battery, and instructions. VII The Development Goals of Robot Baby Artificial intelligence that replicates robot baby behavior could assist a baby in learning from everything it encounters, just like a child does. Facial expressions are a crucial aspect of baby communication because they help babies form bonds with those around them. It is critical to educate robots on empathy by teaching them to understand human behavior and have facial emotions. Dr. Hansen's goal is to build robots that are more intelligent and sympathetic toward humans, and he believes that such emotional expression is far more important than building combat robots. The ultimate goal is for machines to feel and, more significantly, to sympathize. Ⅷ The Influence of Robot Baby Educators all over the world utilize this one-of-a-kind learning tool to teach early childhood, parenting, baby health, and sex education. This smart baby provides meaning and accountability by tracking and reporting on caregiver behavior via wireless programming. Care events, mishandled acts, time in a vehicle seat, and outfit changes are all tracked behaviors. Robot baby includes four sets of curriculum and activities to help instructors create relevant and career-focused learning experiences. The development of the robot baby is critical for scientists studying the human nervous system and doing neural computing. Although researchers acknowledge that many people will be concerned about robot babies that can build more of themselves, they feel that understanding the technology will lead to numerous benefits in the long run.   Ⅸ FAQ 1.How much does a robot Baby cost? The robots, which start at $749, are used in two-thirds of American school districts, according to the manufacturer, Realityworks. One of the benefits of the robots is meant to be the reduction of teen pregnancy, but there is little evidence that they work. 2.How does a real care Baby work? Easy operation: Baby is totally wireless. Users wear an electronic ID on a wristband that ensures RealCare® Baby 3 detects their presence. Rechareable, 6 hours charge will give 7 days operation. Realistic care: Baby requires feeding, burping, rocking and nappy changing. 3.Why do people use fake babies? Some consumers of reborn dolls use them to cope with their grief over a lost child (a memory reborn), or as a portrait doll of a grown child. Others collect reborns as they would regular dolls. These dolls are sometimes played with as if they are an infant. 4.What class gives you a fake baby? RealCare Baby® 3 (formerly known as Baby Think It Over® or BTIO®) is the world's most advanced infant simulator. Educators around the world use this unique learning aid to teach early childhood, parenting, infant health lessons, and sex education. 5.How much does an infant simulator cost? A proper response involved turning a key in its back and holding it for a while. Today, the RealCare Baby 3 infant simulator is a fantastically sophisticated, computer-programmed doll that costs up to $1,000 to replace if you lose it 6.What are the codes for baby simulator? Baby Simulator Codes (Available) PET - Redeem for reward (NEW)Coinsbaby - Redeem for 500 Coins.YAY - Redeem for 2,000 Happiness.Gems - Redeem for 250 Gems.Xmas - Redeem code for 200 Snowflakes.Snow - Redeem code for 50 Snowflakes.Snowing - Redeem code for 150 Snowflakes.Gem20 - Redeem code for 20 Gems. 7. Are the real care baby wristbands waterproof? The bracelets are also tamperproof, ensuring the designated student is completing the simulation.

Introduction Potentiometer is a common instrument that uses compensation principle and comparison method to accurately measure DC potential difference or power supply electromotive force. It has high accuracy, convenient use, and stable and reliable measurement results. But even so, when we do potentiometer experiments, we still have to deal with different error problems. The content of this article tells you how to avoid too many errors without getting too large deviations in the experimental results. Potentiometer Experiment (Compare EMF of Two Cells) Catalog Introduction Ⅰ Potentiometer Principle Analyses 1.1 Compensation Principle 1.2 Operational Principle Ⅱ UJ25 DC Potentiometer Overview Ⅲ UJ25 DC Potentiometer Application 3.1 Working Current Adjustment 3.2 Experimental Content 3.3 Laboratory Apparatus Ⅳ Discussion of Experimental Results Ⅴ FAQ Ⅰ Potentiometer Principle Analyses If you want to firmly acquire the use of the basic potentiometer, you must first understand its compensation principle and operational principle. 1.1 Compensation Principle The electromotive force (EMF) of the power supply is theoretically equal to the voltage of the two poles when there is no net current flowing inside the power supply. If you directly use a voltmeter to measure it, the result is actually the terminal voltage not the EMF. Because the power supply has internal resistance r0, if the voltmeter is directly connected in parallel to the two ends of the power supply, there must be a current I through the inside of it, and also there is inevitably a potential drop Ir0 inside. So the indicated value of the voltmeter is only the terminal voltage of the power supply (U=E-Ir0) size. Obviously, in order to be able to accurately measure the EMF of the power supply, the current I must be zero. At this time, the terminal voltage U of the power supply is equal to its electromotive force E. Figure 1. Closed Loop As shown in the figure on the right, connect the electromotive force as Es, Ex and galvanometer G to form a closed circuit. When Es<Ex, the current direction is as shown in the figure, and the pointer of the galvanometer is biased to one side. When Es>Ex, the direction of current is opposite to the direction shown in the figure, and the pointer of the galvanometer is biased to the other side. Only when Es=Ex, there is no current in the loop. At this time, i=0, and the pointer of the galvanometer is not deflected. We call these two electromotive forces in a compensation state. Conversely, if i=0, then Es=Ex, this method is called zero-show method. 1.2 Operational Principle As shown in the figure, the compensation principle shows that Ex can be determined by measuring Vab. The next step is how to accurately measure Vab. Here, the comparative measurement method is used. Connect Ex to the tap of Rab. When the tap is slid to position Rab, no current flows in G, then Ex=I*Rab, where current I is the main circuit current. Then connect a standard battery EN with known EMF in the circuit, when the tap slides to the position Rcd, G is 0 again, then EN=I*Rcd, where This method is to obtain the ratio relationship between the voltage to be measured and the EMF of the standard battery through the comparison of resistance. Because R is a precision resistance, Rab/Rcd can be read accurately, EN is a standard battery with high-accuracy EMF. Therefore, as long as the auxiliary power supply E is stable and the galvanometer G has sufficient sensitivity during the measurement process, Ex can have a very high measurement accuracy. The voltage measuring instrument made according to the above principle is called a potentiometer. Figure 2. Auxiliary Circuit It should be pointed out that the condition for the establishment of  is that the working current of the auxiliary circuit in the two compensations must be equal. In fact, in order to facilitate the reading, I=EN/Rcd should be standardized, so that the corresponding resistance value can be directly read out abV, which is Ex.Actually, there is no sliding rheostat in the instrument provided to us in the experiment, only 2 resistance boxes. This experiment requires us to use a rheostat box to replace the sliding rheostat. Therefore, we will use a resistor box R1 instead of the compensation method to measure the sliding rheostat RP, the other resistor box R2 acts as Rab. Since the resistance of them can be read directly, we can easily keep the current through the auxiliary circuit unchanged, that is, keeping R1+R2 constant.   Ⅱ UJ25 DC Potentiometer Overview UJ25 DC Potentiometer is a kind of high potential device, the upper limit of measurement is 1.911110V, the accuracy is 0.01 grade, and the working current I=0.1mA. Its principle is shown in the figure, the bottom of the right figure is its panel, and the functions of the upper 12 binding posts have been indicated on the panel. The Rab in the figure is two step resistance knobs, marked with the value of the standard battery EMF at different temperatures for correction when adjusting the working current. RP is used to adjust the working current I. Rcd is the six large knobs marked with voltage values, used to measure the unknown voltage value at the lower left corner of the function switch. When it is off, the potentiometer does not work; when it is at N, it can be connected to check and adjust the working current. When it is at X1 or X2, it can measure the unknown voltage of the first channel and obtain the second channel. The three buttons marked G0, G1, and short circuit are the control switches for rapid current detection. By being in the off state and pressing G0, the galvanometer is on in the circuit, but a large resistor R is connected in series to compensate for the principle. At the same time, protect the galvanometer; press G1 down, the galvanometer is directly connected to the circuit, so that the potentiometer is in a high-sensitivity working state. When the damping switch turns on, the galvanometer coil is short-circuited, and the coil does not swing due to the large electromagnetic damping. Figure 3. UJ25 DC Potentiometer Circuit   Ⅲ UJ25 DC Potentiometer Application 3.1 Working Current Adjustment Turn the function switch to N, turn the temperature compensation resistor Rab to the last two digits of the corrected standard battery EMF "1.018V", press the "G0" and "G1" respectively, and adjust RP to zero for the galvanometer.Measure the voltage to be measured.Switch the function switch to X1 or X2, press the "G0" and "G1" buttons respectively, and adjust Rcd to the galvanometer zero, finally the displayed value is the voltage to be measured. 3.2 Experimental Content 🔺Assemble Potentiometer(1) Design and connect the potentiometer circuit, the following is the standard battery temperature correction formula: (2) Standardize the working current, and measure the electromotive force of the dry battery.(3) Measure the sensitivity of potentiometer. 🔺UJ25 DC PotentiometerUse UJ25 box-type potentiometer to measure dry cell electromotive force. 3.3 Laboratory Apparatus ZX-21 resistance box (two), pointer galvanometer, standard battery, regulated power supply, dry battery to be tested, double pole double throw switch, UJ25 box type potentiometer.Data Processing and Error Quantitative Analysis.🔺Raw DataStandard battery electromotive force: E20=1.01186V, UJ25 measurement Ex=1.469285V, accuracy level 0.01Ambient temperature: T1=20.5℃, T2=21.5℃ EN R1=1018.6Ω R2=1983.8Ω EX R'1=1469.8Ω R'2=1532.6Ω Sensitivity Measurement/14div R''1=1484.1Ω R''2=1518.3Ω 🔺Potentiometer Measurement ResultsStandard Electricity Correction Value where ，get EN=1.01857VPosition battery EMF calculation 🔺Error and Uncertainty Analysis(1) Instrument Error get Similarly Knowing that R1, R2, R'1, R'2 are independent of each other, then the data in (1) can be obtained: (2) Sensitivity ErrorSensitivity  (3) Effects of the Temperature Change Assuming the temperature is constant, then Because of , therefore, this part of the error and its uncertainty can be ignored.(4) EN Stability Because of therefore, this part of the error and its uncertainty can be ignored.(5) Error Analysis and Synthesis of UncertaintyFrom the calculation of (3) and (4), it can be seen that the combination of uncertainty can omit the error of EN indication, and omit the error caused by the change of the auxiliary power supply and the standard battery EN during the two zero indications. Also the sensitivity error of the circuit during the two times of zero display, and because the readings of multiple measurements are almost unchanged. So only one measurement result is recorded and used, and we do not consider the impact of EN error on the measurement of Ex.Compared with the uncertainty of (2) obtained by (1), the uncertainty of (2) is about one-tenth of the uncertainty of (3), but considering that the uncertainty of (3) is of the order of 10^(-3), it can ignore the magnitude of 10^(-4). In the end , get the final result of the measurement.   Ⅳ Discussion of Experimental Results The use of UJ25 potentiometer can more accurately measure the electromotive force of the unknown power source, so as to further analyze the measurement results of the self-assembled potentiometer.Knowing that the measurement result of UJ25 potentiometer is EX=1.469258, and calculate the sensitivity error of the instrument: Because the readings of multiple measurements are consistent, it is ignored.That is, the actual measurement result of UJ25 potentiometer is .The measurement result is .That is, the relative error is .The operation of this experiment is relatively simple, but the data processing is slightly complicated, especially the calculation of uncertainty. Because of its many sources, it is impossible to analyze the errors one by one, so the smaller influencing factors are ignored to simplify the calculation. In this process, we understand that the principle of compensation to eliminate the internal resistance of the electric meter and the battery will be of great help to subsequent experiments.   Ⅴ FAQ 1. What is a potentiometer in a circuit?A potentiometer is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. ... Potentiometers are commonly used to control electrical devices such as volume controls on audio equipment. 2. What is the purpose of the potentiometer?A potentiometer is a type of position sensor. They are used to measure displacement in any direction. Linear potentiometers linearly measure displacement and rotary potentiometers measure rotational displacement. 3. How does a potentiometer affect a circuit?The potentiometer is a three-wire resistive device that acts as a voltage divider producing a continuously variable voltage output signal which is proportional to the physical position of the wiper along the track. 4. What happens when you turn potentiometer?It will behave like a normal resistor. When the circuit is connected to a center lead, and an outside lead, the potentiometer will behave like a variable resistor - turning the post of the potentiometer will increase (clockwise), or decrease (counter-clockwise) the resistance of the potentiometer. 5. How does a potentiometer change resistance?As you turn the knob of a potentiometer, the change in the resistance can be either linear or logarithmic. The way the resistance changes is called the taper. With a linear taper potentiometer, turning a knob a certain amount will change the resistance by a set amount, no matter the position of the knob. 6. How much voltage can a potentiometer handle?The easiest way to think about it is that there is a maximum current through the pot. If you have a 1W 100 ohm potentiometer, the max. current is 100mA (full voltage = 10V); if you are using only 27 ohms of the potentiometer then the max. 7. How does current flow in a potentiometer?Assume V to be the voltage produced by the cell in the primary circuit across the length of the potentiometer wire, and E to be that produced by the cell of the secondary circuit. 8. What is the formula for potentiometer?It is calculated as V/L, where V is the potential difference between two points and L is the distance between two points. Also K = (IρL/A)/L = Iρ/A. 9. How is potentiometer power calculated?Imax = √(P/R) where Imax is the maximum amount of current that can pass safely through any part of the pot, P is the specified power rating of the pot, and R is the specified resistance of the pot. For example, a 10,000-ohm, 1-watt potentiometer can safely pass √[1/(1 x 104)] amperes, or 10 milliamperes. 10. How do you calculate the output voltage of a potentiometer?Measure the total battery voltage, and then measure the voltage between the same two points on the potentiometer (wiper and negative side). Divide the potentiometer's measured output voltage by the measured total voltage. 11. What is the working principle of potentiometer?The principle of a potentiometer is that the potential dropped across a segment of a wire of uniform cross-section carrying a constant current is directly proportional to its length. The potentiometer is a simple device used to measure the electrical potentials (or compare the e.m.f of a cell). 12. What is potentiometer calculate the internal resistance of a cell?To calculate internal resistance, we use a potentiometer to first calculate the voltage across the battery, with no current through it. Then we attach a resistor in parallel to the battery and recalculate the voltage across it. ... Using the battery equation, we calculate the internal resistance. 13. What are the two uses of potentiometer?The applications (uses) of the potentiometer:Voltage divider: The potentiometer can be used as a voltage divider to change the output voltage of a voltage supply.Audio control: Sliding potentiometers are commonly used in modem low-power audio systems as audio control devices. 14. How do you calculate the emf of a cell using a potentiometer?Using a potentiometer, we can determine the emf of a cell by obtaining the balancing length l. Here, the fall of potential along the length l of the potentiometer wire is equal to the emf of the cell, as no current is being drawn from the cell. 15. How can potentiometer be used to calculate potential difference?A Potentiometer can be to measure e.m.f of a cell which cannot be measured by a voltmeter. When a voltmeter is connected in a circuit it draws current through the circuit and thus can measure the potential difference across the cell terminals. ... Thus it measures the e.m.f. of the cell. 16. What is the principle of potentiometer support with equation?The basic potentiometer working principle is based on the fact that the potential across any piece of the wire is directly proportional to the length of the wire, which has a uniform cross-sectional area and the constant current flowing through it. 17. What is potentiometer write its principle and construction?The potentiometer is a device used to compare the e.m.f of two cells. It works on the principle that when a constant current flows through a wire of uniform cross-sectional area, a potential difference between its two points, is directly proportional to the length of the wire between the two points.

Introduction As a beginner, what the functions of capacitors in a circuit? A Capacitor is a passive electronic component that stores and releases the energy. Its unique characteristic is blocking direct current while allowing alternating current to pass. The main functions of capacitors are based on these characteristics. The use of capacitors is also based on this. Here are collecting 20 questions about capacitor use in electronics enclosed with details. Let you have a more comprehensive understanding of the use of capacitors. How Capacitors Work? 20 Questions about the Role of Capacitors in Circuits Help you learn about capacitors functions in 30 minutes. These questions forcus on how capacitors work, where capacitors are used, why capacitors are used, the different types. 1) What is the function of a capacitor connected in parallel with the positive and negative terminals of the voltage source?When cap used in a rectifier circuit, it has a good filtering effect. When the voltage is alternating, the voltage at both ends cannot be changed suddenly due to the charging effect of the capacitor, which ensures the stability of the voltage. When cap used as a battery power supply, it is equivalent to short-circuiting the battery's AC signal, avoiding the increase in battery internal resistance and parasitic oscillation of the circuit due to the battery voltage drop. 2) A capacitor in series or in parallel can achieve the effect of coupling in the circuit. What is the difference between whether there is a capacitor in the circuit?In the AC multi-stage amplifying circuit, because of the different gains and powers of each stage, the DC working offset values of each stage are different. If the levels are directly coupled, it will cause the bias values of all levels to be mixed and unable to work normally. The “Pass AC, Block DC” characteristic not only solves the coupling of inter-stage exchanges, but also isolates the inter-stage biased value intermixing. 3) The two coupling capacitors in the basic amplifying circuit, the positive pole of the capacitor and the DC positive pole are connected to pass the AC and block the DC. Can the reverse connection also have this function?If the connection is reversed, the electrolytic capacitor will leak, which will change the DC operating point of the circuit and make the amplifying circuit abnormal or unable to work. 4) What is the role of the capacitor in the resistance-capacitance coupling amplifier circuit?Block the DC signal so that the static operating points of adjacent amplifying circuits are independent of each other and do not affect each other. 5) Can the analog circuit amplifier do not have a coupling capacitor? The theory in amplifier circuit adds a coupling capacitor between the transformer secondary coil and the transistor. Turn the output of the former stage into the input of the latter stage, so that two stages do not affect. The former stage is alternating current, so does the latter stage, so there no mutual influence.The former stage is indeed alternating current, but the latter stage is alternating current superimposed direct current. The transistor needs a DC bias. If there is no capacitor to block the DC, the coil of the transformer will bypass the DC bias of the transistor (because the inductor passes DC). 6) In the basic amplifier circuit, can the coupling capacitor be non-polar?In the basic amplifying circuit, the coupling capacitor depends on the frequency. When the frequency is high, a non-polar capacitor is needed. It is characterized by relatively stable, high withstand voltage, small size and capacity. Its biggest use is to block direct current and pass alternating current. Coupling capacitor is widely used in high-frequency alternating current paths, bypass, resonance and other circuits. (high-pass)When the frequency is low, since the capacitance of the non-polar capacitor is relatively low, the capacitive reactance is relatively increased, so it is necessary to use a polar electrolytic capacitor. Because of the electrolyte inside, the capacity can be made large, allowing low-frequency alternating current to pass. However, because of the organic medium between the internal two poles, the withstand voltage is limited. Non-polar capacitor is mostly used in circuits such as low-frequency AC paths, filtering, decoupling, and bypassing. (low-pass) 7) In a battery-powered circuit, why does the capacitor charging and discharging have the delay effect?Capacitors accumulate electric charge. During the charging process, the voltage rises slowly, while discharging vice versa. During charging, at the beginning, the voltage across the capacitor is zero, as the time goes by, the voltage gradually rises to the voltage you set to control the switching of the circuit. Of course, the discharging process can also be used to achieve this. The delay time is related to capacitor capacity, capacitor leakage, charging resistance, voltage, and sometimes the load resistance is also taken into consideration. 8) The resistance-capacitance coupling amplifier circuit can only amplify AC signals, but cannot amplify DC signals?Capacitor is an electronic component that blocks DC and AC. Therefore, the resistance-capacitance coupling amplifier circuit can only amplify AC signals. A direct coupling amplifier circuit is used to amplify DC signals. 9) How to tell the coupling capacitor and the bypass capacitor in the amplifying circuit?The negative pole of the coupling capacitor is not grounded, but is connected to the input of the next stage, and the negative pole of the bypass capacitor is grounded. 10) How to choose coupling capacitor for the multi-stage AC amplifier circuit?Generally ceramic capacitors can be done, and tantalum capacitors can be used if the performance is good. According to the frequency range of your input signal, capacitance of 103,104 can be used for high frequencies, and also electrolytic capacitors of about 22uF can be used for lower frequency AC signals. 11) The amplifying circuit adopts direct coupling, and the feedback network is a pure resistor network. Why is the circuit only possible to produce high-frequency oscillation?The oscillation comes from the phase shift of the closed loop reaching 180 degrees and the loop gain at this time is greater than zero. Using a pure resistor network as a feedback network will definitely not have phase shift, which comes from the open loop circuit of the amplifier only. Using a direct-coupled open-loop amplifier, there will be no capacitive elements between stages that will cause phase shifts, but the capacitor inside the transistor or MOS tube will cause it. These capacitances are all fF, the maximum is pF. The resonant frequency of the circuit composed of these capacitors and the equivalent resistance of the circuit is quite high. Therefore, the amplifier adopts direct coupling, with a pure resistor feedback network, which can only produce high-frequency oscillations. 12) How to estimate the output resistance of the first-stage amplifier and the input resistance of the second-stage amplifier? When the amplitude of the signal source is too large, what will happen at the output of the two-stage amplifier? Shake the input end of the amplifier and observe the output end to see what appears? why?A. The input resistance of the second stage amplifier is the output resistance of the first stage amplifier. B. Have distortion. C. Cause clutter due to human body induction. 13) How to use the charge and discharge of capacitors to understand filtering, decoupling and bypassing?Capacitors block DC and pass AC. Blocking DC is easy to understand, but passing AC is not easy to understand. As long as you understand it, you can understand filtering, decoupling and bypass.Capacitors are charging and discharging, but the direction of alternating current changes alternately. The magnitude of the amplitude also changes periodically. The entire changing image is a sine curve.The capacitor is connected to the AC circuit, and due to the periodic change of the AC voltage, it is also periodically changes. There is a charging and discharging current in the line. This charging and discharging current has the same shape as the voltage except that the phase is 90 degrees ahead of the voltage, which is equivalent to the AC passing through the capacitor.The alternating current passing through the resistance consumes electric energy (heating) on the resistor. However, the capacitor only exchanges energy with the power supply. The power supply sends energy to the capacitor when charging, and the capacitor returns the electrical energy to the power supply when discharging. Therefore, the power generated by multiplying the voltage by the current here is called reactive power.What needs to be clear is that when the capacitor is connected to an AC circuit, the flowing electrons (current) do not really rush through the insulating layer, but generate current in the circuit. This is because in the circuit, reverse discharge and forward charge are in the same direction, the forward discharge and reverse charge either. Understand that the capacitor is connected to AC, then the AC component is bypassed to the ground, and also the filtering is completed. 14) How to use bypass capacitor, filter capacitor and decoupling capacitor respectively?These three types of capacitors are actually used for filtering, but they are used in different circuits, so their names and usages are different.Filter capacitor, this is the capacitor we usually use after power rectification. It is a capacitor that rectifies the AC of the rectifier circuit into a pulsating DC and smoothes it by charging and discharging. This type of capacitor is generally an electrolytic capacitor with a large capacity.Bypass capacitors are used to filter out the high frequency components in the input signal. They are mainly used to filter high frequency clutter. Usually, ceramic capacitors and polyester capacitors are used. The capacity is small and is at the picofarad level.The decoupling capacitor takes the interference of the output signal as the filtering object. It is equivalent to the battery and uses its charge and discharge so that the amplified signal will not be interfered by the sudden change of the current. Its capacity depends on the frequency of the signal and the degree of ripple suppression. 15) Regarding the function of the capacitor, under what circumstances use the coupling capacitor and under what circumstances use the filtering capacitor?After the alternating voltage is applied to the two ends of the capacitor, it will continue to charge and discharge with the alternating frequency of the current. At this time, there is an alternating current of the same frequency in the circuit, which is the passing characteristic of the capacitor.When the frequency is appropriate, the capacitor can be regarded as a path to the circuit, and the AC output of the previous stage can be transmitted to the subsequent circuit through the capacitor.For direct current, it is isolated, because when the voltage at both ends is charged to be equal to the circuit voltage, there will be no more charging current.When acting on the transmission of front and rear AC signals, it is coupling, and when acting on filtering out fluctuation components and useless AC components, it is filtering. 16) The capacitor filter of the rectifier circuit uses its charge and discharge, but sometimes the filter uses the capacitor to have a different capacitive reactance to the non-pass frequency signal, such as a bypass capacitor. So which point is used when analyzing capacitor filtering?The theoretical explanation of using capacitor characteristic is more general, and the theory using capacitive reactance is more in-depth. The role of capacitor is to use its charge and discharge characteristics, depending on what components you want to filter out. Use large capacitors to filter low frequencies and a small capacitor for high frequency. In theory, the filtering in the low-frequency rectifier circuit and the bypassing in the high-frequency circuit are the same, and the difference is the capacitive reactance. 17) After the filter capacitor is fully charged, it will discharge the back circuit and then in cycle?Such a working process in the circuit, capacitor is related to the frequency of the signal. First of all, it depends on what you want to put the capacitor in the circuit. When used as a filter, it filters out a certain frequency signal to the ground. For example, the capacitors at the front end of the chip power supply are decoupling. The phenomenon you mentioned is like the filter capacitor before the voltage regulator is turned off and the filter capacitor of the switching power supply. 18) What is the specific coupling of capacitors? Is there any difference compared with filtering?Coupling refers to the process of signal transmission from the first stage to the second stage, and usually refers to AC coupling when it is not specified. Decoupling refers to taking further filtering measures on the power supply to remove the influence of mutual interference between the two levels of signals through the power supply. The coupling constant refers to the time constant corresponding to the product of the coupling capacitance value and the second-stage input impedance value.Decoupling has three purposes: D.Remove the high-frequency ripple in the power supply, and cut off the high-frequency signal of the multi-stage amplifier through the crosstalk path of the power supply.E.When the large signal is working, the circuit's demand for the power supply increases, causing the power supply fluctuations, here decoupling reduces the impact of power fluctuations on the input stage/high voltage gain stage during large signals.F. Form a floating ground or floating power supply, and complete the coordination of various parts of the ground or power supply in a complex system.The high-frequency switching noise generated by the active device during switching will propagate along the power line. The main function of the decoupling capacitor is to provide a local DC power supply to the active device to reduce the noise on the board and to guide it to the ground. 19) How to distinguish whether the capacitor in the circuit is a filter capacitor or a bypass capacitor?The filter capacitor is in the power circuit; the bypass capacitor is in the signal circuit.In fact, their function is basically the same. The filter capacitor: Bypasses or filters out the pulsating current components and plays the role of charging and discharging. Bypass capacitor: Filter or bypass high frequency or low frequency components in the circuit. 20) Is the coupling capacitor a decoupling capacitor?It is completely different. The coupling capacitor is for signal transmission, and the decoupling capacitor is for reducing interference.

IntroductionThe Temperature Sensor, a measuring instrument, uses various physical properties of a substance to convert the thermal quantity into the physical quantity, including expansion, resistance, capacitance, electromotive force, magnetic properties, frequency, optical characteristics and thermal noise. Many materials and components change with temperature, so there are quite a few materials that can be used as temperature sensors. Here are four temperature sensors in detail.Temperature Sensors ExplainedCatalogIntroductionⅠ Temperature Sensor Types Overview1.1 What is Thermocouple?1.2 What is Thermistor Sensor?1.3 What is Resistance Temperature Detector (RTD)?1.4 What is IC Sensor?1.5 Temperature Sensor Cons and ProsⅡ How to Test: Measuring IndexesⅢ FAQⅠ Temperature Sensor Types OverviewThere are many types of temperature sensors, which can be divided into contact type and non-contact type according to the measurement method; thermistor and thermocouple according to the characteristics of sensor materials and electronic components.The contact temperature sensor needs to maintain thermal contact with the measured medium, so that the two can perform sufficient heat exchange to reach the same temperature. This type of sensor mainly includes resistance type, thermocouple, PN junction temperature sensor and so on. The non-contact temperature sensor does not need to be in contact with the measured medium, but achieves the purpose of temperature measurement through the heat radiation or convection of the measured medium.Here is a detailed introduction to the commonly used four: Thermocouples, Thermistors, Resistance Temperature Detector (RTD), IC Sensor.Figure 1. Temp Sensors (Resistance Changes with Temperature)1.1 What is Thermocouple?Thermocouples are the most commonly used temperature sensors in measurement. Its main advantages are wide temperature range and adaptability to various atmospheric environments, and it is strong, low in price, does not require power supply, and is also the cheapest. The thermocouple consists of two different metal wires connected at one end. When one end of the thermocouple is heated, there is an electric potential difference in the thermocouple circuit, and the measured electric potential difference can be used to calculate the temperature.Figure 2. Metal JunctionsThe thermocouple sensor has two contacts. The measurement end (sometimes called the hot end) is where the two metals connect. The reference junction (also called the cold end) is connected to the measurement circuit. When there is a temperature difference between two ends, an mV signal proportional to the temperature difference is generated. The mV value increases with increasing temperature. The relationship between mV and temperature is non-linear.The thermocouple connector can be constructed by connecting the thermal junction to the outer sheath for grounding or ungrounding (insulating from the sheath). A grounded thermocouple responds faster, but the thermocouple will contact the processing voltage. Therefore, it is important to isolate the measurement circuit to prevent the formation of ground loops and to avoid measurement errors.Figure 3. Thermocouple for Temperature MeasurementInside the temperature component, the thermocouple is usually embedded in magnesium oxide (MgO) and a metal sheath, then insert it into the thermowell or protective tube. This helps protect the sensor from environmental pollution. When magnesium oxide is contaminated with water and salt, even thermocouples that are not grounded will eventually be grounded.As above mentioned, the relationship between voltage and temperature is nonlinear, so it is necessary to make a second measurement for the reference temperature (Tref), and use the test equipment software or hardware to process the voltage-temperature conversion inside the instrument to finally obtain the thermocouple temperature (Tx). Thermocouple is the simplest and most versatile temperature sensor, but its sensitivity is relatively low, which is easy to be affected by environmental interference signals, and the temperature drift of the preamplifier. So it is not suitable for measuring small temperature changes, that is, it is not suitable for high-accurate measurement and application.In actual use, the thermocouple measuring circuit can measure any temperature except 0°C. The measuring circuit must measure the temperature of the cold junction and restore the temperature to 0°C. This kind of electrical compensation is called cold junction compensation (or reference junction compensation). Most thermocouple measurement circuits do this.If the application requires a thermocouple instead of a thermistor, a higher-grade thermocouple is better. In addition, their cost difference is small, and high-quality wire can provide higher stability.🔺Table 1: Thermocouple Types and Application RangesThermocouple TypeApplication Range (℃ / ℉)E95-900℃ (200-1650℉)J95-760℃ (200-1400℉)K95-1260℃ (200-2300℉)N95-1260℃ (200-2300℉)R870-1450℃ (1600-2640℉)S980-1450℃ (1800-2640℉)T0-350℃ (32-660℉) 1.2 What is Thermistor Sensor?The main component of the thermistor sensor is the thermistor, which absorbs heat radiation around.Thermistors are made of semiconductor materials, mostly with a negative temperature coefficient, that is, the resistance decreases with increasing temperature. Temperature changes will cause large resistance changes, so it is the most sensitive temperature sensor. However, the linearity of the thermistor is extremely poor and has huge effects with the production process. So the manufacturer cannot give a standardized thermistor curve.The thermistor is very small and responds quickly to temperature changes. But it needs to use a current source, and its small size also makes it extremely sensitive to self-heating errors.Figure 4. Thermistor SensorThe thermistor measures the absolute temperature on the two lines, with better accuracy, but it is more expensive than a thermocouple, and the measurable temperature range is also smaller than that of a thermocouple. A commonly used thermistor has a resistance value of 5kΩ at 25°C, and a temperature change of 1°C causes a resistance change of 200Ω. Note that the lead resistance of 10Ω only causes a negligible error of 0.05°C. It is very suitable for current control applications that require fast and sensitive temperature measurement. Small size is benefit for applications with space requirements, but care must be taken to prevent self-heating errors.Figure 5. Resistance-TemperatureThe thermistor also has its own measurement tips. With small size, it can quickly stabilize, and will not cause thermal load. However, it is not strong enough, and large currents can cause self-heating. Since the thermistor is a resistive device, any current source will cause heat on it due to power. Power is equal to the product of current squared and resistance. Therefore, a small current source must be used. If the thermistor is exposed to high heat, it will cause permanent damage. 1.3 What is Resistance Temperature Detector (RTD)?RTD is a precision temperature sensor, made of high-purity conductive metal (such as platinum, copper or nickel) or alloy. Its resistance increases with increasing temperature and decreases with decreasing temperature, similar to a thermistor. RTD is like a thermoelectric converter, converting temperature changes into voltage changes. By passing a constant temperature current through the temperature sensor, an output voltage that increases linearly with temperature can be obtained. The most suitable metal for RTD is a pure metal that remains stable within a given temperature range. The resistance-temperature change relationship is preferably linear. The larger the temperature coefficient (it is defined as the resistance change caused by unit temperature), the better, and it must be able to resist thermal fatigue and respond sensitively to temperature changes. A typical RTD has a protective sleeve and a probe. The protective sleeve is mainly used to protect the RTD from being damaged by the measured medium, which is usually made of stainless steel, carbon steel, inconel or cast iron, and its use temperature can reach 1100°C.Figure 6. Resistance Temperature Detector (RTD)It is currently the most accurate and stable sensor, and its linearity is better than thermocouples and thermistors. However, RTD is also a temperature sensor with slow response speed and more expensive price. So it is most suitable for applications that have strict requirements on accuracy, but speed and price are not critical. 1.4 What is IC Sensor?IC sensors can work in a temperature range of -55°C to +150°C, and precise one can operate at temperatures up to +200°C. It is commonly used in fitness tracking applications, wearable products, computing systems, data loggers, and automotive applications. The most common integrated IC temperature sensors are analog output devices, digital interface devices, remote temperature sensors, and those integrated ICs with thermostat functions.Figure 7. IC Sensors (Thermometer)Analog output devices (usually output voltage, but some also output current) are most like passive solutions when they need an ADC to process the output signal. Digital interface devices most often use a two-wire interface (I2C or PMBus) and have a built-in ADC. In addition to including a local temperature sensor, remote temperature sensors also have one or more inputs to monitor the remote diode temperature—they are most often placed in highly integrated digital ICs (for example, processors or field programmable gate arrays FPGA). When reached the temperature threshold, the thermostat can provide a simple alarm.Here are the details of two common types:🔺Analog Output Temperature SensorThe integrated sensor is made using silicon semiconductor integration process, so it is also called a silicon sensor or a monolithic integrated temperature sensor. It is a dedicated IC that integrates a temperature sensor on a chip and can take temperature measurement and then output analog signals. The main features of this sensor are single function (only measuring temperature), small temperature measurement error, low price, fast response speed, long transmission distance, small size, micro power consumption, etc., which are suitable for long-distance temperature measurement, control and measurement. What’s more, non-linear calibration doesn’t required, and the peripheral circuit is simple.🔺Digital Output SensorDigital temperature sensor is the product of microelectronics technology, computer technology and automatic test technology (ATE). The intelligent temperature sensor contains temperature sensor, A/D converter, signal processor, memory (or register) and interface circuit. Some products also come with multiplexers, central controller, random access memory and read-only memory. The characteristic of the intelligent temperature sensor is that it can output temperature data and related temperature control quantities, adapts to various microcontrollers (MCU). It realizes the test function through software on the basis of hardware, and its intelligent harmony also depends the level of software development.1.5 Temperature Sensor Cons and Pros🔺Table 2: Advantages and Disadvantages of thermocouples, RTDs, thermistors and IC sensors.CriteriaThermocoupleRTDThermistorIC SensorTemperature-250℃ to +750℃-100℃ to +500℃-267℃ to +2316℃-55℃ to +200℃AccuracyBestDepends on calibrationGoodGoodLinearityGoodWorstGoodBestSensitivityLessBestWorstGoodCircuityComplexDepends on accuracy/power requirementsComplexSimplestPower ConsumptionHigh when takingLow-highLowest Ⅱ How to Test: Measuring Indexes1) Measurement accuracy: 0.01 level2) Resolution 0.1uV and 0.1mΩ3) Scan switch parasitic potential: ≤0.4μV4) Temperature range: Water tank: (room temperature +5~95)°C; Oil tank: (95 ~ 300)°C; Low & constant temperature bath: (-80 ~ 100)°C; High temperature furnace: (300~1200)°C5) Temperature control stability: better than 0.01℃/10min (oil tank, water tank, low temperature constant temperature tank); 0.2℃/min (tube type verification furnace)6) Total uncertainty: For thermocouple verification, measurement uncertainty is better than 0.7 ℃, repeatability error <0.25 ℃; For thermistor verification, measurement uncertainty is better than 50 mk, repeatability error <10 mk7) Working power supply: AC220V±10%, 50Hz, and well protected grounding.8) High temperature furnace power: about 2kW9) Constant temperature bath power: about 2kW10) Power of microcomputer measurement and control system: <500 Ⅲ FAQ1. What is temperature sensor and how it works?How do temperature sensors work? They are devices to measure temperature readings through electrical signals. The sensor is made up of two metals, which generate electrical voltage or resistance once it notices a change in temperature. ... Temperature is the most common physical measurement type in industrial applications. 2. What happens when a temperature sensor goes bad?If the coolant temperature sensor goes bad it can send a false signal to the computer and throw off the fuel and timing calculations. ... This will cause the computer to think the engine is cold, even when it is not, and as a result will use more fuel than necessary. 3. Which temperature sensor is best?The most well-known are Pt100 (with a resistance of 100 ohms at 0°C) and Pt1000 (with a resistance of 1,000 ohms at 0°C). The Pt1000 offers better accuracy and a larger tolerance to long wire lengths than the Pt100. Compared to thermocouples, resistance sensors offer better accuracy and a more linear response. 4. What is the application of temperature sensor?Within our homes, temperature sensors are used in many electrical appliances, from our refrigerators and freezers to help regulate and maintain cold temperatures as well as within stoves and ovens to ensure that they heat to the required levels for cooking, air confectioners/heaters. 5. How do I know if my temperature sensor is bad?What Signs May Signal Your Coolant Temperature Sensor May Be Failing.Poor Fuel Economy.Irregular Temperature Readings.Black Smoke from Your Exhaust.Your Engine is Overheating.Your Check Engine Light is On. 6. How important sensors are nowadays?Intelligent sensor systems are omnipresent in our everyday lives. They provide security, save lives and improve our quality of life. As more and more areas of life are automated and networked, the importance of innovative sensor technologies will also increase in the future. 7. What should I consider when choose a temperature sensor?Several factors must be considered when selecting the type of sensor to be used in a specific application: temperature range, accuracy, response time, stability, linearity, and sensitivity. 8. What is the value range of a temperature sensor?The effective operating range is -50 to 250 °C for glass encapsulated thermistors or 150°C for standard thermistors. 9. What are the pros and cons thermocouple?Advantages and disadvantages of thermocoupleAdvantages of thermocouple: Simple working principle, Short response time, Low price, Wide temperature ranges, Rugged construction, Self-powered, Small size.Disadvantages of thermocouple: Nonlinearity, Accuracy, Interference can cause errors. Old technology, Needs calibration, Corrosion. 10. What is difference between PT100 and RTD?There is no difference a PT100 is a version of a RTD (resistance temperature detector). What is an RTD? A resistance temperature detector, also known as an RTD or resistance thermometer, is a type of temperature sensor. ... A PT100 sensor is the most common type of Resistance Thermometer (RTD).