Overview

Adafruit carries a lovely foot switch which has a single pole-double throw switch inside.  The switch can activate a number of items including an alarm or powerswitch tail to control your world.

A much-requested project by Adafruit customers is using the foot switch to interface with a PC via universal serial bus (USB).  To get a switch activation to talk to the USB bus takes a controller - some smarts.  

Adafruit's ATtiny85 based Trinket is low cost and contains enough smarts to perform USB communication (via some smart library software).

Only three parts are required.  The foot switch, a USB cable, and a Trinket 5V.  The entire project costs less than $20.  And it takes less than an hour's work.

The wiring is shown above.  The existing foot switch wires are cut short and two connected to Trinket pins #0 and GND (ground).  When the foot switch is activated, the switch contact pair that creates a short connects Pin #0 with ground. When the Trinket detects the pin connected to ground, it outputs one or more characters as a PC keyboard.

The Trinket Keyboard tutorial states a Trinket 5V should be used due to the microcontroller clock rate the library uses.

As you take apart and reassemble the switch, there are some small parts you will want to keep track of for reassembly.
Last updated on 2016-09-27 at 09.35.50 PM Published on 2015-01-20 at 11.33.22 AM