This project uses three blue and three green buttons and a tri-color LED that shows the winner’s color or red for a tie. Nine 2-input AND gates use 4081 ICs, while three 3-input OR gates use one 4075 IC. Multiple button presses activate at least two LED colors, signaling an invalid move.

Any button press powers the circuit. Each button connects to the ICs supply through a low-voltage-drop 1N5819 diode and to the logic through a 1N4148, a higher voltage-drop diode, preventing CMOS inputs from exceeding the supply voltage and damaging the ICs.

Rock, Paper, Scissors Rules

Rock crushes scissors – Win Rock

Scissors cut paper - Win Scissors

Paper covers rock - Win Paper

A match is a tie.

Nine 2-input AND gates detect the valid outcomes: three wins per player and three ties. Three 3-input OR gates combine the results and control the tri-color LED: green or blue shows the winner, and red shows a tie.

The board required three revisions. I labeled the logic-gate functions (AND/OR) on the schematic to simplify design verification. Early in the design process, I created a spreadsheet to map the possible combinations. I used the AND and OR logic functions to test the design in the spreadsheet.

RPS.zip contains the KiCad project files and RPSTemplate.pdf, a printable case-drilling template.

The wide-pin tri-color LED and push buttons with colored caps were the hardest parts to source, and I have found them only on Amazon. The components, including push buttons without colored caps, are readily available from Digi-Key and other suppliers. I found the battery holder on Digi-Key but not on Amazon.

You may adapt this project for your own version or use it as the starting point for a new design.