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What's wrong with this circuit? The mosfet will turn on just fine with 5v or the gpio 3.3v but i cannot get it to turn off. It will only turn off if I use another external power supply for the Raspberry Pi and connect the GNDs. But with this circuit it just won't turn off. Why is that?

note: there's a 2n3906 pnp transistor between gpio pin and Drain.

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    \$\begingroup\$ What do you expect the circuit to do? It looks like you have ground connected to both the drain and source of the mosfet. How do you know it's allowing current to flow? It's possible I don't totally understand the diagram \$\endgroup\$ – Essaim Nov 15 '17 at 3:15
  • \$\begingroup\$ Also, how does the switch control the raspberry pi? \$\endgroup\$ – Essaim Nov 15 '17 at 3:23
  • \$\begingroup\$ Probably the transistor is turning off, but there is some overlooked alternate pathway from Raspberry Pi board GND to 5V Boost Gnd. Can you show the full detail of how the PNP is connected? \$\endgroup\$ – mkeith Nov 15 '17 at 3:31
  • \$\begingroup\$ I turn on the switch and the mosfet turns on which turns on the raspberry pi which turns on the gpio pin high. if i turn off the switch it should signal the raspberry pi to shutdown and pull low the gpio pin. \$\endgroup\$ – colofofong Nov 15 '17 at 3:33
  • \$\begingroup\$ Isn't the gpio pin then holding the mosfet's gate above the threshold voltage? \$\endgroup\$ – Essaim Nov 15 '17 at 3:38

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