power control

  1. Doktor Jones

    P-channel mosfet and 555 for power-on delay?

    It's been forever and a day since I've been here, but I'm dipping my toes back into electronics design Anyways, I have a "dumb" device that's connected to a hat on my Raspberry Pi 4. Unfortunately, due to some signaling issues with the dumb device, if it's on when the Pi powers on, the Pi gets...
  2. L

    LM317 no reference voltage

    Hello all, This is my first post so forgive me if I break any rules, I am trying to create a variable voltage power supply using an lm317 but am running into problems. For starters, it doesn't seem that I have a vref voltage, when probed I get 0 volts across input and adjust. My second problem...
  3. I

    Question about switching between 220v and 12v

    Hi, I'm an engineer but not in the field of electronics. I live in the countryside and here the water comes from a 0.5HP electric water pump to the house, from a water tank. There are power outages quite often in winter, so I have some batteries with a solar panel and a inverter to manually...