Peltier + NPN + MOSFET

If your FET gate has a lot of capacitance, you need enough resistor to keep from drawing more than 40mA when turning the FET ON.

5V / .04A = 125R minimum.

The FET board has 1K built in so no chance of exceeding 40mA. Small (805 or 603) SMD component so would not recommend changing unless experienced / right equipment. According to my simulation 1K makes for sluggish turn on / off but acceptable for this application. FET dissipation <0.5W when switched at 10KHz.


Didn’t realize that what you had was a manufactured module - not a couple of FETS connected together. The 2N7000 does nothing except drive the indicator LED. The IRLR8113 is driven direct by the Arduino output. The module already has a 1K ohm limiting resistor in the IRLR8113 gate lead, so there is no need for your external 1K resistor. Leave it out. Including it will slow the switching time down excessively. It is slow enough due to the internal resistor.
I did a simulation on the circuit and although switching is slow, it works OK in this application.
IRLR8113 dissipation is <500mW, (@ PWM of 10KHz) which is OK - it will get warm but not excessively hot.

Give it a go - it should work and it should not be possible to easily do any damage.

Note that the mosfets, being wired onto a board, have reasonable protection against static damage, so no special handling precautions are needed. Be careful however, not to drop scraps of wire, tools, splashes of solder etc onto a powered board - nothing protects against that sort of disaster.

If you are using a UNO or any of the others with a DC input socket, you should be able to use this to power the Arduino from your 12V supply. I am doing this on my current project where just about all the peripherals run on 12V. I have no separate supply for the Arduino.


Thank you for all the trouble! Will give it a try!