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74HC595: Circuit Design of LED Driver

Author: Mia
Date: 9 Oct 2020
 1568
Circuit Design of LED Driver

I. Introduction

The 74HC595 is an 8-bit serial-in or parallel-out shift register with a storage register and 3-state outputs. 74HC595 with the characteristics of high speed, low power consumption and simple operation, can be easily used in MCU interface to drive LED operation. This article introduces the circuit design of LED display drived by 74HC595.

Catalog

I. Introduction

II. Basic Description

2.1 LED Display

2.2 74HC595

III. Circuit Design

3.1 Hardware Circuit

3.2 Display Driver

IV.  Conclusion

FAQ

Ordering & Quantity

II. Basic Description

2.1 LED Display

A 7 Segment LED Display, also known as LED display, has been widely used in various instruments because of its low price, low power consumption and reliable performance. There are many types of LED drivers on the market, and most of them have multiple functions, but the price is correspondingly higher. If used in a simple system with low cost, it is not only a waste of resources, but also increases the cost of products. Using 74HC595 chip to drive LED has various disadvantages. High speed, low power consumption, unlimited number of LEDs. It can control both the common cathode LED display and the common anode LED display. The circuit designed with 74HC595 is not only simple, but also low in power consumption and strong in driving ability. It is a low cost and flexible design scheme.

2.2 74HC595

The 74HC595 is an 8-bit serial-in/serial or parallel-out shift register with a storage register and 3-state outputs. Both the shift and storage register have separate clocks. The device features a serial input (DS) and a serial output (Q7S) to enable cascading and an asynchronous reset MR input. A LOW on MR will reset the shift register. Data is shifted on the LOW-to-HIGH transitions of the SHCP input. The data in the shift register is transferred to the storage register on a LOW-to-HIGH transition of the STCP input. If both clocks are connected together, the shift register will always be one clock pulse ahead of the storage register. Data in the storage register appears at the output whenever the output enable input (OE) is LOW. A HIGH on OE causes the outputs to assume a high-impedance OFF-state. Operation of the OE input does not affect the state of the registers. Inputs include clamp diodes. This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC.

Figure 1. 74HC595 Functional Diagram

Figure 2. 74HC595 Logic Symbol

III. Circuit Design

3.1 Hardware Circuit

Figure 3 is a display panel circuit designed with AT89C2051 and 74HC595 interface.

Figure 3. Circuit of Display Panel

The P115, P116, and P117 of the P1 port are used to control the display of the LED, and they are connected to the SLCK, SCLK and SDA pins respectively. Three digital tubes are used to display the voltage value. On the circuit board, LED3 is on the far left and LED1 is on the far right. When sending data, first send the display code of LED3, and finally send the display code of LED1. The brightness of the LED is controlled by the resistance of PR1 to PR3.

2.2 Display Driver

Use DISP1, DISP2, and DISP3 to store display data. After the CPU initialization is complete, call the LRDISP subroutine to clear the register of 74HC595. There is no need to call the clear subroutine before calling the display subroutine DISPLAY. Now write the two subroutines as follows.

CLRDISP:

MOVR2,#24

CLRBIT:

CLRSCLK

CLRC

MOVSDA,C

SETBSCLK

DJNZR2,CLRBIT

RET

Display:

CLRSLCK

MOVR3,#3

MOVR0,#DISP3

DISP1:

MOVA,@R0

MOVR2,#8

DISP2:

CLRSCLK

RLCA

MOVSDA,C

SETBSCLK

DJNZR2,DISP2

DECR0

DJNZR3,DISP1

SETBSLCK

RET

IV. Conclusion

It can be seen from the above examples that there are no complicated technical problems in the design of hardware and software when 74HC595 is used to design LED driver circuit. In addition, 74HC595 can be used not only to drive LED displays, but also to drive light-emitting diodes. Each 74HC595 can drive 8 LEDs simultaneously. This solution is ideal when the volume requirements of the product are not high and want to reduce the cost.

 


FAQ

  • What is 74HC595?

74HC595 is a shift register which works on Serial IN Parallel OUT protocol. It receives data serially from the microcontroller and then sends out this data through parallel pins. We can increase our output pins by 8 using the single chip.

  • What is a 74hc595n?

8-bit Shift Register 74HC595N

A shift register is a chip you can use to control many outputs (8 here) at the same time while only using a few pins (3 here) of your Arduino.

  • How does a shift register work?

Shift registers hold the data in their memory which is moved or “shifted” to their required positions on each clock pulse. Each clock pulse shifts the contents of the register one bit position to either the left or the right.

  • How 74HC595 Shift Regiester works?

The 595 has two registers (which can be thought of as “memory containers”), each with just 8 bits of data. The first one is called the Shift Register. The Shift Register lies deep within the IC circuits, quietly accepting input.

  • How does an 8 bit shift register work?

The SN74HC595N is a simple 8-bit shift register IC. Simply put, this shift register is a device that allows additional inputs or outputs to be added to a microcontroller by converting data between parallel and serial formats. Your chosen microprocessor is able to communicate with the The SN74HC595N using serial information then gathers or outputs information in a parallel (multi-pin) format. Essentially it takes 8 bits from the serial input and then outputs them to 8 pins.

Ordering & Quality

Photo Mfr. Part # Company Description Package PDF Qty Pricing
(USD)
74HC595BQ-115 74HC595BQ-115 Company:Nexperia USA Inc. Remark:IC 8BIT SHIFT REGISTER 16-DHVQFN Package:16-VFQFN Exposed Pad
DataSheet
In Stock:87000
Inquiry
Price:
3000+: $0.10346
6000+: $0.09719
15000+: $0.09092
30000+: $0.08339
75000+: $0.08026
150000+: $0.07712
Inquiry
74HC595D-112 74HC595D-112 Company:Nexperia USA Inc. Remark:IC SHIFT REGISTER 8BIT 16SOIC Package:16-SOIC (0.154", 3.90mm Width)
DataSheet
In Stock:5102
Inquiry
Price:
1+: $0.38000
10+: $0.31100
25+: $0.28440
100+: $0.21150
250+: $0.19168
500+: $0.15864
1000+: $0.11898
2500+: $0.10906
5000+: $0.10246
Inquiry
74HC595D-118 74HC595D-118 Company:Nexperia USA Inc. Remark:IC SHIFT REGISTER 8BIT 16SOIC Package:16-SOIC (0.154", 3.90mm Width)
DataSheet
In Stock:82500
Inquiry
Price:
2500+: $0.08960
5000+: $0.08463
12500+: $0.07716
25000+: $0.07218
62500+: $0.06471
125000+: $0.06223
Inquiry
74HC595N-112 74HC595N-112 Company:Rochester Electronics, LLC Remark:SERIAL IN PARALLEL OUT Package:16-DIP (0.300", 7.62mm)
DataSheet
In Stock:On Order
Inquiry
Price:
658+: $0.38000
Inquiry
74HC595PW-112 74HC595PW-112 Company:Nexperia USA Inc. Remark:Shift Shift Register Element Bit 16-TSSOP Package:16-TSSOP (0.173", 4.40mm Width)
N/A
In Stock:On Order
Inquiry
Price:
1+: $0.34000
10+: $0.27600
25+: $0.25240
100+: $0.18790
250+: $0.17024
500+: $0.14090
1000+: $0.10568
2500+: $0.09687
5000+: $0.09100
Inquiry
74HC595PW-118 74HC595PW-118 Company:Nexperia USA Inc. Remark:IC SHIFT REGISTER 8BIT 16TSSOP Package:16-TSSOP (0.173", 4.40mm Width)
DataSheet
In Stock:217500
Inquiry
Price:
2500+: $0.09108
5000+: $0.08602
12500+: $0.07843
25000+: $0.07337
62500+: $0.06578
125000+: $0.06325
Inquiry
74HC595PW-AUJ 74HC595PW-AUJ Company:NXP USA Inc. Remark:IC COUNTER REGISTER 8BIT 16TSSOP Package:16-TSSOP (0.173", 4.40mm Width)
DataSheet
In Stock:On Order
Inquiry
Price:
Call
Inquiry
74HC595PW-C1118 74HC595PW-C1118 Company:NXP USA Inc. Remark:Shift Shift Register Element Bit 16-TSSOP Package:16-TSSOP (0.173", 4.40mm Width)
N/A
In Stock:On Order
Inquiry
Price:
3435+: $0.07000
Inquiry
74HC595PW-Q100-118 74HC595PW-Q100-118 Company:Nexperia USA Inc. Remark:Shift Shift Register Element Bit 16-TSSOP Package:16-TSSOP (0.173", 4.40mm Width)
N/A
In Stock:On Order
Inquiry
Price:
1+: $0.39000
10+: $0.33000
25+: $0.30800
100+: $0.24630
250+: $0.22872
500+: $0.19354
1000+: $0.14955
2500+: $0.13768
5000+: $0.12880
12500+: $0.11991
25000+: $0.11688
Inquiry
CD74HC595NS CD74HC595NS Company:Texas Instruments Remark:Shift Shift Register 1 Element 8 Bit 16-SO Package:16-SOIC (0.209"", 5.30mm Width)
DataSheet
In Stock:On Order
Inquiry
Price:
Call
Inquiry

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