I am trying to make a cooler using Peltier Modules, the Peltier Modules and the fans switch on when the Temperature sensor attached to the circuit reads above a certain threshold. But I know that Arduino can only handle a couple of MilliAmps as its functionality, in such a case, how can I control my 480W circuitry (12V/40A) using Arduino?

I'm very new to all this and will appreciate a detailed answer.

EDIT: To the best of my knowledge, this is not a duplicate of another question as the other question says I'm currently working on several projects that each require controlling devices ranging from 800mA to 2A from an Arduino Uno., whereas my application requires much larger current than that.

  • @gre_gor Edited the question to address your concern.
    – Kv07
    Jul 4, 2018 at 20:07

2 Answers 2


There are solid-state relays (such as this one) capable of switching the currents - 40A - you're talking about and may be a better choice than a mechanical one. Note that it will probably need to be mounted to a heat-sink.

You're Arduino then only needs to drive enough current to switch the relay. The example I gave above is not a recommendation as I've never used it; it's just the first one I found that is spec'd for enough more than 40 Amps to not be operating at its limit. I'm sure there are others as well.

The current it will draw from the Arduino is not specified; this is something you will need to find out about whatever relay you choose, to be sure it won't exceed the Arduino's 20 mA pin-driver spec. It is spec'd to require a heat sink.

  • 1
    When the relay draws more current, than the Arduino's pin can provide, you can simply use a small transistor to switch this current
    – chrisl
    Jul 4, 2018 at 15:20

You are correct the Arduino can only handle a few mA at 5V. In order to do what you want you need to use the Arduino to switch relays that can handle the current.

  • Where can I get the relevant info to work with these relays? I tried looking up on the internet but the stuff was a bit too complex for a new tinkerer like me.
    – Kv07
    Jul 4, 2018 at 12:07
  • You are looking for one of the multitude of blue cubes that google will return if you search for "12V 40W relay". The problem is narrowing it down to one that meets you requirements. You have two connections on the logic side, + and -, which are your switching lines connected to the Arduino. On the other side there are usually 3 connections, Com[mon], NO(Normally Open) and NC(Normally Closed). With no voltage applied at the logic side the NO connection will be switched off, the NC connection will be switched on. When you apply a logic voltage NO switches on and NC switches off. Jul 4, 2018 at 12:22
  • 1
    The ratings/voltages are usually printed on the relay. Jul 4, 2018 at 12:22
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    Make sure your check de DC rating, not the AC rating. DC ratings tend to be a lot lower.
    – Gerben
    Jul 4, 2018 at 18:10
  • @Gerben can you elaborate?
    – Kv07
    Jul 4, 2018 at 20:08

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