Parts List

Use any of these: a pressure mat switch (the flat kind from door chimes, under $2), a thin-film pressure sensor like the RP-S40-ST (under $3), or make your own from two sheets of aluminum foil separated by a piece of foam with a hole cut in the center. The RP-S40-ST works in V1 — wire it in series. The harder someone presses, the brighter the LED glows.

The soft kind, not the bright clear ones. Diffused LEDs scatter the light for a warm glow. About $0.25 each.

The flat silver one. 3V. Same battery used in the Swamp Glow build. Available at any drugstore, grocery store, or online. About $0.45 each in a 20-pack.

Black electrical tape. Holds the wiring connections together. Any hardware store or dollar store.

ATTINY85-20PU. Same chip used in the Swamp Glow build. Tiny 8-pin microcontroller — program it once, it remembers forever. Runs on 2.7–5.5V. 5-pack for $13.99 — gives you spares.

A flat resistive strip — resistance drops when pressed. About the size of a finger. Reads as analog input on the ATtiny85. Thin enough to hide under a cushion or mat. Under $3.

Pull-down resistor for the pressure sensor. 1/4 watt. Brown-black-orange color bands. Connects Pin 7 to GND so the analog reading stays low when nobody is pressing the sensor. 100-pack.

Same programmer used in the Swamp Glow build. USB programmer board with a built-in socket. Plug the ATtiny85 in, plug into USB, upload from the Arduino IDE. $16.99.

LED current limiter. 1/4 watt. Brown-green-brown color bands. 100-pack for $5.49.

Same holder used in the Swamp Glow build. Snap-in holder with red (+) and black (−) wires and built-in on/off switch. Red wire to VCC (pin 8), black wire to GND (pin 4). No extra hookup wire needed. 6-pack for $5.59.

VERSION 3 — GO FURTHER

Building Version 3? You still need the pressure mat from Version 1. No soldering required for the ATOM Matrix itself — just two jumper wires and a resistor to the mat.