Making A Single 74HC595 Seven Segments Driver For Arduino PIC And AVR

Overview

Using 74HC595 shift registers, we can drive any display such as 7-segment or a dot matrix. It saves the controller pins with only three control signals requirements. These control signals are:

1. Serial Clock
2. Serial Data
3. Enable pin

Two extra power supply pins are VCC and GND. Using these three pins we can drive a large amount of shift register as we need, for example 10 8-bit shift register.

A sample images of SN74HC595N from online store.

 

Pins And Logic Diagram Of SN74HC595

 

Timing Diagram

 

I make a single seven segments board driven by a single 74HC595 shift registers. I remove this single seven segments from an HP Print/Scan/Copy machine.

 

Fully Solder Board

 

Copper Side After I Soldered.

This board is made using a simple toner-transfer method. I use my own HP laser printer with my hot plate iron at home.

Schematic Diagram. The SSD is common anode type.

The SSD I used here is common anode type. I added three 1N4148 switching diode to reduce the voltage. Since each 1N4148 has a voltage drop of ~1V, thus three of this could make a voltage drop of ~3V. The SSD needs only ~2V of nominal working voltage.

A screen shot of PCB design

High Quality Print Copper Side.

An optional components side

I took a 3D view of this PCB.

 

Design file could be downloaded here. The file Proteus 8 format. Please use the latest version to open.

Arduino Test Program

Arduino is popular due to ease of programming. I test this board with Arduino Uno I possess. I use shiftOut() function to interface to 74HC595. This function is considered as a software SPI. We can declare any pin on Arduino to shift out clock and data.

 

The syntax of shiftOut() is:

 

shiftOut(dataPin, clockPin, bitOrder, value)

 

Where,

• dataPin - Serial data output synchronizes with clock
• clockPin - Serial clock output 
• bitOrder - Decide which bit order to transfer first. It could be MSBFIRST or LSBFIRST
• value - An 8-bit data to transfer   

 In this programming interface I use board to display value between 0 and F, since the hexa decimal has 16 values.

 

The sketch is shown below.

 

Arduino Test Program

 

Counting reaches 0x0A is hex.

 

Arduino test program could be download here. 

 

 

 We can use the ATMega32 microcontroller to interface to some serial to parallel shift registers chips.

1. ATMega32 Interfaces To SN74HC164 Shift Registers
2. ATMega32 SPI Interfaces To SN74HC164 And LED 
3. ATMega32 SPI Interfaces To SN74HC164 And LCD Using 3 Pins
4.  ATMega32 And SN74HC164 Serial Seven Segment Display
5. ATMega32 SN74HC164 Seven Segments Display And Switch Interfacing 
6. ATMega32 SN74HC164 Three-Digit Multiplexing Display
7. ATMega32 SPI Interfaces With SN74HC595 For Character LCD Controlling