How can I detect a load is connected to a MOSFET and report that back to the MCU? So the MOSFET can be ON or OFF, but I need to know in both situations if there's something connected or not.

NOTE: if it involves an additional GPIO, then id like to add an indicator LED instead.


simulate this circuit – Schematic created using CircuitLab

  • 2
    \$\begingroup\$ Please draw a schematic of how everything is connected. Can you live with say 1 uA leaking into your load? \$\endgroup\$ – winny Oct 22 '20 at 9:21
  • \$\begingroup\$ Perhaps using a smart switch, instead? Also, the load can be few micro amperes or several tens of amperes, so how would a device report its state? \$\endgroup\$ – Marko Buršič Oct 22 '20 at 9:55
  • 4
    \$\begingroup\$ When the MOSFET is on, measure current as the voltage across a small sense resistor between the MOSFET and the supply rail it switches. When it is OFF place a high value resistor across the FET to leak a little bit of current into a load, and see if there's full voltage across the empty terminals, or a reduced one across a load which is present. For more specifics you will have to edit your question to provide more details \$\endgroup\$ – Chris Stratton Oct 22 '20 at 10:32
  • \$\begingroup\$ @MarkoBuršič can you give an example of a smart switch? \$\endgroup\$ – Seeker Oct 22 '20 at 10:38
  • \$\begingroup\$ You can download some app notes on Infineon, NXP, ...any other manufacturer that produces MOSFET smart switches for automotive, industry, ...etc \$\endgroup\$ – Marko Buršič Oct 22 '20 at 11:12

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.