Shift Registers

Controlling (mixing) inputs (push buttons) and outputs (LEDs) with the 74HC595 IC.

Contents

• Background
• Main goal
• Cases
  • One shift register (74HC595): 4 inputs and 4 outputs
  • Two daisy-chained shift registers (74HC595): 8 inputs and 8 outputs
  • Three daisy-chained shift registers (74HC595): 12 inputs and 11 outputs
• Results

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Background

Work inspired by and adapted from Kevin Darrah's video on How to Control a Ton of Inputs using Shift Registers!. Note: In the video, Kevin shared and explained his great idea as well as his code. However, schematics/diagrams are missing, what makes the process a bit difficult to follow. In case you're wondering, this image describes the main idea:

Main goal

My goal is to optimize my Soccer Penalty Kicks Game's control, which is currently working with 2 analog input reads based on resistors, controlling 12 push buttons, which, as mentioned by Kevin in his video, becomes problematic at the end of the day when having a number of inputs.

While Kevin's work handles multiple buttons (like a piano), my control has only one active button, so in the code, as soon as I identify a button press, I exit the button inspection and only light one LED.

Cases

One shift register (74HC595): 4 inputs and 4 outputs

See the source code.

Two daisy-chained shift registers (74HC595): 8 inputs and 8 outputs

See the source code.

Three daisy-chained shift registers (74HC595): 12 inputs and 11 outputs

This is what I actually needed for my game. One of the buttons triggers another action and is not connected to any LED, that's why the odd numbers :).

See the source code.

Parts

Amount	Part
11	Red LED
11	330Ω Resistor
12	Push button
12	Diode 1N4001
1	10kΩ Resistor
3	Ceramic capacitor 1µF
1	Electrolytic capacitor 100µF
3	74HC595 Shift Register
1	Arduino Uno (Rev3) - ICSP

3_daisy_chained_shift_registers_12_inputs_11_outputs.mp4

Results

This is how the control looks ike after implementing Kevin's approach.

penalty_kicks_goalkeeper_control.mp4