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  • Contents

I. 74HC164 Introduction

74HC164 adopts DIP-14, SO-14, SSOP-14  and TSSOP  -14 package pin configuration. It is complementary to MOS 8-bit serial input and parallel output unidirectional shift register, the logic symbol is shown in figure 1. The power supply voltage is 2~6V. In figure 1, A and B are the serial code input terminalsCLR  is the clear input terminalCLK  is the clock pulse input terminal. With the arrival of the rising edge of the clock pulse, the state of phase A, phase B, and the subsequent phase shifts from QA to QH in turn.

Catalog

I. 74HC164 Introduction

II. 74HC164 Logic Symbol

III. Circuit Design

IV. How to Check and Repair the Circuit

FAQ

Ordering & Quantity

II. 74HC164 Logic Symbol

74hc164 logic symbol

Figure 1 74HC164 Logic Symbol

III. Circuit Design

Figure 2 is an instrument circuit composed of serial input and parallel output digital integrated circuits. T2-T5, C5, and resistance together form a turn signal flashing oscillation circuit. When the DR (connected to the turn switch) in J8 is disconnected, this circuit will not work and the turn signal will not flash; when DR is on, the oscillation circuit starts to work, the turn signal starts to flash.

Figure 2 Meter circuit diagram

Figure 2 Meter circuit diagram

DR is a three-position switch, one pole is connected to the left turn signal.  One pole is connected to the right turn signal, one pole is suspended in the air, and the other end of the pole hits the ground.

 

The switch-off circuit is composed of Tl, DLRll, and R12. A switch-type Hall element is installed in the front and rear brakes of the electric bicycle. When the switch is switched, the Hall element outputs a low potential, that is, the BRK terminal in the plug J2 is grounded, Tl is turned on, and there is a voltage of nearly 5V on the collector of Tl. This voltage is sent to the controller through the BRK terminal in J2, and the power supply circuit of the motor is turned off. The motor stops working and acts as a brake. On the contrary, when the brake is not pinched, the Hall element outputs a high potential, Tl is cut off, and the motor runs normally.

 

Because 74HC164 is an 8-bit serial input and a parallel output shift register.  it forms a movement mode and battery power display circuit with light-emitting diodes. 74HC164's output pin 13, pin 11, and D5-D7 form the side of the sports mode display circuit, and pins 6 and 10 and D8-D12 form the battery power display circuit. The display signal from the controller is sent to the serial input terminals 1 and 2 of the 74HC164  through the DATA terminal in the J2, and then shifted by the internal circuit, the driving signal is output from the relevant output terminal to light up the corresponding light-emitting diode,  so as to complete the control of the display circuit.

IV. How to Check and Repair the Circuit

This circuit is relatively simple and easy to repair. The main basis for repairing is to judge the quality of 74HC164. First, check whether the +5V voltage is normal, and then check whether the voltage at pin ③ of the 74HC164's clock signal input is close to +5V. If it is lower than +5V, and after disconnecting R73, the CLK terminal voltage of J2 is normal, and the 74HC164 is damaged. If the voltage of the CLK  port is abnormal, the fault is in the controller. Next, measure whether the voltage of the serial input terminals ①and ② changes during the transition of the motion mode. If not, the fault is in the controller; if there is, the 74HC164 is damaged. From the actual repair situation, most of the 74HC164 failures are caused by damage to the internal circuit of the ⑩ pin (power supply terminal). In addition, when purchasing 74HC164.  You can first measure the resistance of the ⑩ pin. The resistance value should be about 4kD in the positive test and infinite in the reverse test.


FAQ

  • How does the 74HC164 transmit data in the microcontroller circuit?

  1. One pin of the single-chip microcomputer is like a faucet, and the data is sent one by one, that is, like the water from the faucet, dripping drop by drop. The 74H164 is like a small bowl receiving water. It is just full after receiving 8 drops of water. At this time, it is sent to the digital tube.
  2. The single-chip microcomputer must send an 8-bit (or more) data, if it is sent at the same time, it is a parallel transmission, if it is a bit by bit, it is a serial transmission. The data of the single-chip microcomputer is sent to the 74HC164 bit by bit, which is serial, and the 74HC164 sends the data to the digital tube at once, which is parallel. So 74HC164 plays a role from serial transmissionto paralleltransmission.
  • What is the difference between 74HC164D and 74HC164N MCU?

The D in 74HC164D represents a chip package. The N in 74HC164N means dual in-line plastic packaging.

  • What is the difference between 74HC164 and 74LS164, can they be used together?

74ls164 is a TTL circuit, the power supply voltage is 5V, the high-level output current Ioh is -0.4MA, and the low-level output current is 8MA.

74HC164 is a CMOS circuit, the power supply voltage is 2V ~ 6V, the output drive current can reach plus or minus 20MA. If the power supply voltage you use is 5V and the output drive current is suitable for 74ls164, they can be used together.

  • What devices can 74hc164 be replaced with?

74HC164 is a CMOS device with a power supply voltage of 2V-6V. It can be directly replaced by 74HCT164, 40H164. If the power supply voltage is 5V and the output drive current is small, it can also be replaced by 74164, 74LS164, 74F164, 74ALS164.

  • Which of 74LS164 and 74HC164 has higher driving capability?

74LS164 is a TTL device with a high-level driving capability of about 0.4mA and a low-level driving capability of about 8mA. 74HC164 is a CMOS device, with high-level and low-level drive capability up to 20mA. The above data comes from DATASHEET. But generally speaking, the high-level output capability of many CMOS devices is weak, smaller than TTL, and the low-level drive capability is stronger.

  • Can 74hc164n be used to drive the digital tube?

Of course, you can use the 164 chip to drive the nixie tube, which is mostly used in situations where the IO port resources are tight and the display data refresh of the nixie tube is slow. When designing the circuit, multiple 164 chips are used in cascade, no matter how many digital tubes are driven, only 2 IO ports of the single-chip microcomputer are occupied. It can be said that it is the most IO port-saving driving method, and it is still driven statically, without strobe and brightness Low phenomenon.

The disadvantage is that multiple 164s are used in cascade connection, which will cause the single-chip microcomputer to send a large amount of display data (1 byte per nixie tube) at one time when refreshing the display data. During this process, the nixie tube will be all on, although the data is sent The process duration is very short, but it still affects the display effect. It is recommended to turn off the digital tube when refreshing the data.

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