New to post, but I come here often. So I am working on building a small fermentation chamber and i want to control the temperature using two Peltier's. One for hot and one for cold. I'm using two to help prevent thermal shock, and also use the way temperature works with heat rising and cold falling.

I have read a fair bit from this forum and others, but I can't find the answer to my basic questions.

Can I use a transistor as a switch to turn on and off a Peltier without any real problems?

I've seen a few posts about using a h-bridge ,or a variety of tec controllers. But none of the posts go into good detail, and I'm not that good on programming.

My basic design is to use an Arduino connected to a temperature sensor and the two Peltier's connected to the transistors and the power supply. Add a bunch of fans to circulate air, and program it turn hot on below x point and cold on above y point.

If there is a post that does answer my question sorry for the double post. But any help is appreciated. If you have questions about my project please feel free to ask. Thanks for the help.

EDIT: I am on working on the theory right now. I have not committed to any parts yet. I have been looking at easily available Peltier's usually running on 12V and varying amps. Everything else was gonna be commonly available parts.

My end goal is to have a controllable fermentation chamber, with commonly available parts, that's easy and cheap enough others to build. Most of the things I've seen are lacking information, or have too much complexity.

  • \$\begingroup\$ How closely do you need to control the temperature? How much current and at what voltage will your Peltier junction draw? \$\endgroup\$
    – Eric Urban
    May 25, 2016 at 1:46
  • \$\begingroup\$ Most of the recipes I've looked over have around a 3-5 degree Fahrenheit range. The peltier's I was looking at run on 12 volts and range from 3-15 amps. \$\endgroup\$
    – chris h
    May 25, 2016 at 3:16
  • \$\begingroup\$ My suggestion is you just use a prebuilt relay board. You can use some relays to turn the power on and off. You can use a single peltier junction to heat and cool things. When reverse current is sent through the junction it is just a heater. \$\endgroup\$
    – Eric Urban
    May 25, 2016 at 3:26
  • \$\begingroup\$ I understand they can be run in reverse. See response below. Also I've seen pairs cheaper or at the same price as single units. I can see relays being used. I have more experience with transistors and that's why I chose them. \$\endgroup\$
    – chris h
    May 25, 2016 at 4:19

1 Answer 1


Yes - a transistor or MOSFET of an appropriate size and rating will easily control one or more Peltier cells.

You are aware that a Peltier cell can both heat and cool simply by reversing the polarity of the DC voltage feeding the cell?

If you give us more information regarding your setup, we can provide more information.

What is the voltage and current rating of your Peltier cells?

What power supply voltage do you want to run from?

FWIW - many Peltier coolers and heaters run from Automotive power supply nominal 12 Vdc.

  • \$\begingroup\$ I understand that they can be run both ways by reversing the polarity. I was going to use 2 so I can have one placed near the top of the box to be the cold one. And one at the bottom to be the hot one. Heat rises, cold falls. I also want to prevent thermal shock even though the likelihood in my application is low. I was going to make the chamber out of foam insulation boards, probably 2'x2'x4'. \$\endgroup\$
    – chris h
    May 25, 2016 at 3:52
  • \$\begingroup\$ Heatsinks both sides with air forced through them. Along with the fans on the heat sink I would probably have an additional 4 fans to ensure even air flow through the chamber. I'm debating on where to place the thermostat. I'm probably going to go in the chamber first, but may move it into the fermenter at a later time. \$\endgroup\$
    – chris h
    May 25, 2016 at 4:06

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.