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i have a kobo with a serial port output providing 3.3v when the device is turned on.

i want to use it to control a microcontroller 5v board with esp32 on it drawing max 200mA directly from the battery (so they share common ground)

note:despite the fact esp32 is 3.3v the board i use can only be powered w/ 5v

i’m wondering what is the best solution between

  • mosfet
  • bjt transistors
  • relays
  • and possibly other.

also what components should i use given i want i) no consumption when kobo is off ii) minimal consumption when kobo is on

bobleponge
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1 Answers1

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MOSFETs switch "loadless" basicaly it has a tiny capasitor inside that if charged opens the MOSFET

BJT(Bipolar Junktion Transistors) switches with a "load" basicaly if the Base to Emiter Voltage is Positive or Negative (depending on if it is a NPN or PNP type)it opens. (not 100% sure please correct me if im wrong)

A Relay uses a Coil to pull a Contact closed.

In my opinion MOSFETs are the best option here, spesificaly as a Lowlevel switch as its easyer to build.(Connect Source to Supply, Connect Gate to your GPIO pin of the ESP, Connect Drain to Ground)

Please do some reseach in case ive missed something.

mss0406
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    "Connect Source to Supply, Connect Gate to your GPIO pin of the ESP, Connect Drain to Ground" - this sentence could be correct, but there's enough ambiguity that it can lead to miswiring. I think you wanted to state something more like source to ground of supply, and drain to ground of load, and specifically N-Type (not P-type) MOSFET, i.e. something like https://electronics.stackexchange.com/q/18884/9612, picture (3)? – nanofarad Apr 26 '22 at 19:29
  • which is an appropriate mosfet for 3.3v to swtich 5v@200mA then? – bobleponge Apr 26 '22 at 20:05
  • oh yeah @nanofarad is right – mss0406 Apr 27 '22 at 05:19