We have an installation that provides:

  • a common line (C), which divides into two wires;
  • an input line (I), which carries the signal from a button (between I and C there's normally 0V, and 12V when the button is pressed);
  • an output line (O), which carries a signal to a bell (between O and C there's always 12V).


simulate this circuit – Schematic created using CircuitLab

A controller is to close the OC circuit every time a given temporal pattern shows in I (say, a concrete Morse-like -short/long- sequence of pulses), so the bell will ring if the concrete word is recognized at the input. Such a controller has been implemented in C++ and uploaded to an Arduino Nano, and it works fine on a protoboard, with a button as input and led as output, all in the same electrical range.

Since both the IC and the OC are 12V circuits, and the controller is in the 5V range, what is the minimal circuit to embed the controller between the IC and the OC circuits?


3 Answers 3



1) use a transistor's b-c junction;

2) use a mosfet;

3) use a relay, solid state or mechanical;

4) find a chip with 12-compliant pins;



Just use a transistor that can handle 12V with the base connected to the Arduino and that's it...

Maybe I didn't get what you were trying to say, but anyway, I think that's what you are looking for.


I think you can use "mosfet" control 12v with 5v voltage also if you think this is insufficient you can add the relay, control relay with mosfet without how much voltage as you want. I made disco lights with rgb strip led and when I run the circuit different time and different type of led turn on and turn off I used 3 mosfets and 3 arduino outputs the strip led work with 12v.

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