simple usb e-brake I made using an old USB keyboard 

you will need some sort of switch. I used a micro switch from an old microwave but you can basically use any type of momentary switch. you will also need an old keyboard. 

use a multi-meter to find the 2 contacts that correspond to the key you want to use for e-break, and solder the switch wires to the contacts on the board. in my case I used the space bar

you'll also need a bolt and locknut for the pivot, and some rubber bands for the spring bac

k. 

throw, feel, and activation force fully customizable by adjusting rubber bands and switch position. I also added felt pads to the switch lever to soften the activation