SSD Booting : low power issue

[Techstyle]

I started off just installing a power switch.  momentary switch was connected across pins 39 (GND) and 40 (GPIO21).  an LED was connected up between pin 38 (GPIO20) and the same GND (39).

In the file /boot/config.txt (use sudo nano /boot/config.txt)

Add the following:

#on/off switch
dtoverlay=gpio-shutdown,gpio_pin=21
dtoverlay=gpio-poweroff,gpiopin=20,active_low="y"

this will command a shutdown when pin 21 is grounded and then when power is off, pin 20 will go low - this is a simple demonstrator and works well (and you can prototype with simple components)

mine looked like this:
     
   
simple and easy to use, but breakers got switched off...