Uploaded July 2018 | Updated September 2026, 2 weeks ago
Pretty cool one here I came up with. Starting with this simple latch circuit I talked about a while back: youtu.be/SntdiUYmp4s
NOTE! Put a 1k resistor right at the base of those two NPN transistors. You never want to have two transistor bases tied together like that.
I wanted to use this to power up my raspberry Pi project, which is pretty easy, but I also wanted to use this to power down as well. Since you can't just kill power suddenly to the Pi, I enabled GPIO21 to go HIGH after a safe shutdown:
sudo nano /boot/config.txt
Adding in this line at the end:
dtoverlay=gpio-poweroff,gpiopin=21
Then from the processing sketch be able to monitor that same pushbutton and determine when to execute the shutdown command. That code zipped up here:
kevindarrah.com/download/laserTargetApp_7_8_18.zip
And the pinout for the GPIO Header: https://pinout.xyz
Oh and make sure to check out the last video on exactly how I got the Pi setup the way you see it in this video: youtu.be/4vdnGZWjBTk
Check out my Tindie store (trigBoard is available) tindie.com/stores/kdcircuits
Thanks to all the Patrons for dropping a few bucks in the tip jar to help make these videos happen!
patreon.com/kdarrah
Twitter: twitter.com/KDcircuits
For inquiries or design services:
kdcircuits.com
Pretty cool one here I came up with. Starting with this simple latch circuit I talked about a while back: youtu.be/SntdiUYmp4s
NOTE! Put a 1k resistor right at the base of those two NPN transistors. You never want to have two transistor bases tied together like that.
I wanted to use this to power up my raspberry Pi project, which is pretty easy, but I also wanted to use this to power down as well. Since you can't just kill power suddenly to the Pi, I enabled GPIO21 to go HIGH after a safe shutdown:
sudo nano /boot/config.txt
Adding in this line at the end:
dtoverlay=gpio-poweroff,gpiopin=21
Then from the processing sketch be able to monitor that same pushbutton and determine when to execute the shutdown command. That code zipped up here:
kevindarrah.com/download/laserTargetApp_7_8_18.zip
And the pinout for the GPIO Header: https://pinout.xyz
Oh and make sure to check out the last video on exactly how I got the Pi setup the way you see it in this video: youtu.be/4vdnGZWjBTk
Check out my Tindie store (trigBoard is available) tindie.com/stores/kdcircuits
Thanks to all the Patrons for dropping a few bucks in the tip jar to help make these videos happen!
patreon.com/kdarrah
Twitter: twitter.com/KDcircuits
For inquiries or design services:
kdcircuits.com
