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LM358 Circuit: Voice Control Delay Switch (With Example)

  • Contents

I Description

This blog mainly introduces the use of the LM358 integrated operational amplifier. We also introduce how to use the LM385 chip to implement a voice-activated delay switch circuit. In addition, the blog also analyzes circuit compositioncircuit analysis, and circuit production and debugging. This circuit we will discuss has the following advantages: small size, economical and practical, easy to make, and intuitive. Therefore, LM358 is especially suitable for beginners' circuit learning.

LM358

Catalog

I Description

II Introduction

2.1 Voice-activated delay switch

2.2 lm358

III Circuit function and schematic diagram

IV Circuit analysis

4.1 Linear part

4.2 Non-linear part

V Circuit production and debugging

VI Conclusion

Component Datasheet

FAQ

Ordering & Quantity

II Introduction

2.1 Voice-activated delay switch

What is a voice-activated delay switch? The voice-activated delay switch is mainly used in the corridor of a residential area or office. The function of this switch is that only after dark when someone walks through the stairway and makes footsteps or other sounds, the corridor lights will automatically light up to provide illumination. When people enter the house or walk out of the apartment, the corridor lights will automatically turn off after a delay of 30 seconds to achieve the purpose of energy-saving.

The working principle of the LM358-based circuit introduced in this blog is simple and easy to understand, suitable for beginners' circuit production.

2.2 LM358

LM358 is a dual operational amplifier. There are two independent operational amplifiers with high gain and internal frequency compensation inside, which are suitable for a single power supply with a wide range of power supply voltage, and also suitable for dual power supply operation mode. In addition, under the recommended operating conditions, the power supply current is independent of the power supply voltage. The scope of application of LM358 includes sensor amplifiers, DC gain modules, and all other occasions where operational amplifiers can be powered by a single power supply.

The features of LM358 are as follows:

  • Internally Frequency Compensated for Unity Gain
  • Large DC Voltage Gain: 100 dB 
  • Wide Bandwidth (Unity Gain): 1 MHz (Temperature Compensated)
  • Wide Power Supply Range:

– Single Supply: 3V to 32V
– Or Dual Supplies: ±1.5V to ±16V

  • Very Low Supply Current Drain (500 μA)—Essentially Independent of Supply Voltage
  • Low Input Offset Voltage: 2 mV
  • Input Common-Mode Voltage Range Includes Ground
  • Differential Input Voltage Range Equal to the Power Supply Voltage
  • Large Output Voltage Swing
  • Unique Characteristics:

– In the Linear Mode the Input Common-Mode Voltage Range Includes Ground and the Output Voltage Can Also Swing to Ground, even though Operated from Only a Single Power Supply Voltage. 

– The Unity Gain Cross Frequency is Temperature Compensated.

– The Input Bias Current is also Temperature Compensated.

III Circuit function and schematic diagram

The LM358-based circuit uses an integrated operational amplifier, and the basic circuit in terms of linearity and nonlinearity is used to make a voice-activated delay switch. The circuit is shown in Figure 1.

lm358 circuit

 

Figure 1. LM358 sound control delay switch circuit diagram

This circuit uses electret microphones to collect sound signals. First of all, amplify the signal with an inverted proportional amplifier circuit composed of an integrated operational amplifier LM358. Subsequently, the voltage comparator composed of LM358 is used to control the relay to turn on.

IV Circuit analysis

4.1 Linear part

The linear part of the circuit shown is the sound amplifier circuit, which is composed of an electret microphone and an inverted proportional amplifier circuit

The inverse proportional amplifying circuit in this circuit is implemented by LM358. LM358 contains two independent, high-gain dual operational amplifiers, suitable for a single power supply with a wide range of power supply voltage. At the same time, it is also suitable for dual power supply mode.

The electret microphone in this circuit converts sound waves into electrical signals, and the inverted proportional amplifier circuit amplifies the electrical signals and provides them to the subsequent circuits. The two capacitors C1 and C2 are coupling capacitors. The signal amplification factor of this circuit is:

4.2 Non-linear part

The non-linear part is a voltage-controlled delay switch circuit. The sound signal collected by the electret microphone is amplified by an inverted proportional amplifier circuit and then coupled via C2 to turn on the diode VD1 and charge the capacitor C3.

When the charging voltage rises to Uth=[R7/(R5+R7)]VCC, the voltage comparator outputs a high level, and the transistor is saturated and turned on. At this time, the relay coil is energized, the switch K is closed, and the light-emitting diode is on.

There is no sound from outside at this time. The diode VD1 is turned off, and the capacitor C3 discharges to R6. When the discharge voltage drops to Uth, the voltage comparator outputs a low level, and the transistor is cut off. At this time, the relay coil is powered off, the switch K is off, and the light-emitting diode is off.

V Circuit production and debugging

First, list the components according to the schematic diagram, and then check each component. We need to make sure everything is correct before we start welding the circuit. It is shown in Figure 2 after completion.

 

Figure 2. Physical picture of LM358 circuit

Finally, connect the 9V DC power supply to debug the circuit. When sound is emitted to the electret microphone, the corresponding three diodes will light up. After a period of delay, the light will go out. Then adjust the resistance of the variable resistor and the corresponding delay time changes happened.

VI Conclusion

The voice-activated delay switch circuit described in this article is designed based on LM358 components. Beginners can further deepen the application of the LM358 integrated operational amplifier through the study of this circuit, and can better grasp the welding technology of the circuit and the troubleshooting method of the circuit fault.


Component Datasheet

LM358 Datasheet


FAQ

  • What is lm358 op amp?

LM358 is a dual op-amp IC integrated with two op-amps powered by a common power supply. It can be considered as one half of LM324 Quad op-amp which contains four op-amps with common power supply. The differential input voltage range can be equal to that of power supply voltage.

  • What is lm358 used for?

LM358 can be used as transducer amplifier, DC gain block etc. It has large dc voltage gain of 100dB. This IC can be operated on wide range of power supply from 3V to 32V for single power supply or from ±1.5V to ±16V for dual power supply and it also support large output voltage swing.

  • Why lm358 is used in IR sensor?

IC Lm358 is used as a comparator when IR receiver senses IR radiations. When the o/p of lm358 goes high, then LED connected at the o/p turns ON. The output pin of the IC LM358 is used to interface with PIC microcontroller.

  • How does an lm358 work?

IC LM358– LM358 consists of two independent, high gain operational amplifiers in one package. Important feature of this IC is that we do not require independent power supply for working of each comparator for wide range of power supply. LM358 can be used as transducer amplifier, DC gain block etc.

  • What is the difference between lm358n and lm358p?

The suffix denotes the manufacturer's packaging code. The 'N' is used by most manufacturers for the plastic 8-pin package. The 'P' is used by a few manufacturers for the plastic 8-pin package. Raven Luni is right, there is NO difference between the two devices, just the mfgrs.

  • How do I know if my lm358 op amp is broken?

Measure the DC voltage at the +input. then measure the DC voltage at the output. if the results are significantly different, the opamp is most likely shot. if they are the same, the opamp is most likely ok and the problem is something else.

  • What is the difference between lm386 and lm358?

The LM386 is a complete audio power amplifier, the LM358 is a dual operational amplifier. When using the LM358 e.g. as a pre-amplifier, you will have to supply a separate power amplifier.

  • What is a dual op amp?

With a dual supply op amp, the V+ terminal of the op receives a positive voltage and the V- terminal connects to negative voltage. Therefore, any input signal fed into the op amp can swing from the positive voltage supply to the negative voltage supply.

  • What is LM series?

The following is a list of LM-series integrated circuits. ... The LM series originated with integrated circuits made by National Semiconductor. The prefix LM stands for linear monolithic, referring to the analog components integrated onto a single piece of silicon.

  • How to import lm358 into LTspice?

1. Download model file and unzip.
2. Place .cir file in same folder as schematic.
3. Place "opamp2" symbol on schematic.
4. Change "opamp2" value to LMX58_LM2904.
5. Place directive on schematic ". lib LMx58_LM2904. CIR" without quotes.

 

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