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I have a piece of electronics that acts as a event sensor and its trigger voltage starts around 3.3V. Lets say that I want to little bit hack this device and hook it up to a button that is on other device. I found out that when I press this button, LED will turn on and there is about 2.3V that can be measured one resistor. If button is pressed again, LED will turn of and there will be 0V.

I want to make this button as an input to the event sensor, but 2.3V is too low voltage to trigger it. I could use Arduino that would read input voltage and I can define trigger threshold there. But I want it to be simple electronics, passive and efficient. Maybe MOSFET or BJT? Can someone give me advice how to do it?

Thank you

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  • \$\begingroup\$ What is the "event sensor"? \$\endgroup\$ – Ron Beyer Aug 12 '20 at 19:43
  • \$\begingroup\$ You can use a transistor as a switch. \$\endgroup\$ – user253751 Aug 12 '20 at 19:48
  • \$\begingroup\$ I've used general term "event sensor". But basically I mean by that is sensor that is triggered by event, like PIR. \$\endgroup\$ – banbananko Aug 12 '20 at 20:00
  • \$\begingroup\$ MOSFETs and BJTs are not passive. \$\endgroup\$ – Andy aka Aug 12 '20 at 20:04
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schematic

simulate this circuit – Schematic created using CircuitLab

This is an inverting switch. R values can be changed

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Use a voltage divider to create a desired trigger level voltage and use a comparator to deliver full (3.3V for example) voltage when that voltage level is reached.

enter image description here

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  • \$\begingroup\$ Thank you for your answer. Could you explain it with schematics? It was a years ago since I used electronics, that's why I'm asking here \$\endgroup\$ – banbananko Aug 12 '20 at 20:02
  • \$\begingroup\$ added schematic to my original answer \$\endgroup\$ – Alex Chumak Aug 12 '20 at 20:20
  • \$\begingroup\$ Thanks, its so simple and I like this approach. \$\endgroup\$ – banbananko Aug 12 '20 at 20:53
  • \$\begingroup\$ Glad you like it. I'm a novice myself but have found comparators to be really neat. So is this the answer you're going with then? Mind marking it as such then? \$\endgroup\$ – Alex Chumak Aug 12 '20 at 21:52

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