Since I printed and start use this case for my Retropie I always imagined how to make a power button. The idea was change the design to make the move button and then move a switch. In the end I had another idea, where I didn’t need change the case. Using a 555 as monostable I done a touch switch.

Step 1: Parts

1 - LM555 timer
1 - 2N7000 FET
1 - 10k resistor
1 - 100k resistor
1 - 330k resistor
1 - 680k resistor
1 - 10nF capacitor
1 - 10uF capacitor
1 - Universal PCB

Step 2: How To

The circuit is simple, when pin 2 of 555 receive the pulse of “finger” the 10uF capacitor start your charge and the output 555 (pin 3) goes to high level and then when the capacitor stop charge the output goes to low level. For the Raspberry Pi turn on is required that the pin 5 (GPIO3) go to low level. For do this was used a FET 2N7000 and a resistive divider, where a resistive divider delivery 3.3V to pin 5 of Raspberry Pi and when the gate of FET receive the high level, the 3.3V signal goes to low working as a switch.