Pololu simple motor controller 18v7


for my project on using a peltier to heat and cool things,
i am curious as to whether i could use a pololu simple motor controller 18v7 to control my 15.4V max, 7A max peltier module in terms of the bi-directional polarity. i know the motor controller should work for a motor but am unsure if it can work for a peltier.

secondly, do i need to use the arduino microcontroller if i were to use this pololu motor controller? or can i just simply ignore the need for an arduino and connect the pololu to the computer directly using their own interface?

thanks you


You could probably use the Simple Motor Controllers(SMC) for that. (We have heard of other people using our motor controllers to control Peltier devices before, so whether or not you can depends on the specifics of the Peltier device you want to use.)

The SMCs do feature bidirectional control, and can be controlled over computer via USB or with a microcontroller (like the Arduino platform) over TTL serial. How you control the SMC would depend on how you want to control the Peltier device. For example, if you just want to adjust from your computer how much voltage is supplied by the SMC, you do not need an Arduino. If you want to do anything that requires more control, like changing the supplied voltage automatically after a set time, you would probably need something like an Arduino to take care of the more complex logic and then send signals to the SMC when you want specific things to happen.

By the way, the SMCs can be configured to be controlled by analog voltages, which means you could probably make a system that uses a knob to adjust how much voltage is supplied to your Peltier device. You can learn more about how to do that and other things inside the SMCs’ user’s guide, which can be found under the Resources tabs of their product pages.

- Amanda

Hi, thanks for the reply.

oh in that case since I am using a portable power supply machine which has knobs to allow me to control the magnitude of voltage/current, i would hence not need to use pololu to control the magnitude of voltage. All i need is for it to only control the DIRECTION of the current to change the polarity of the peltier module. in view of this would you recommend if i control both the direction and magnitude of the current through the pololu-computer directly or control direciton on pololu and magnitude via the knobs of the power supply machine? the former seems more straight forward am i right as it allows you to just focus on one source/mode of control.

any advice on this?


The Simple Motor Control Center features a slide bar that allows you to effectively adjust the voltage of the OUT pins on a Simple Motor Controller (SMC). This feature also allows you to reverse the polarity of the power supply connected to VIN on the SMC. So, if you want to control your device from your computer, I recommend controlling both the effective voltage and the direction with the SMC.

If you want to control the voltage directly from your supply, I recommend using a double-pole, double-throw (DPDT) switch like this one from Servo City to reverse the polarity of your adjustable power supply. (Using a switch like that basically allows you to manually flip the positive and negative leads of your supply.)

- Amanda

Hi Amanda,

sorry, been away for a while. Alright i guess then that controlling from the computer will be the best choice. Since this is a 18V7, does it mean that if i were to connect directly from my computer to the pololu simple motor controller which is connected to my peltier, my peltier will still be able to receive 15Volts and 7 amperes? Does the laptop supply that much voltage and current??? no need to use external supply machine right? just checking with you only. no need to use step up voltage/current regulator right? thanks!


Hi, Robin.

The connection from your computer to the Simple Motor Controller will not supply power to your Peltier system; the USB connection is only used to interface with and power the microcontroller on the Simple Motor Controller. You will need to connect a separate power supply to VIN to power your Peltier.

- Amanda

Hi Amanda,

thanks for the prompt reply. could i ask you if controlling the motor speed the same as controlling the temperature of the peltier chip in the motor control center (sliding bar)

I will be using the computer directly to control the direction and magnitude of Vin by the way.
also, for setting the limits of the temperature of the peltier module, do i need to use the analog/RC/microcontroller channels or do any form of reversal/forwarding of limit switches or killing of switches? or can i just control the limits of the temperature of the peltier from the USB mode will do in the motor controller center platform?


By the way, you will get more efficiency from your peltier module if you add a big inductor in series, to smooth out the PWM.

Yes, controlling the motor speed with the slider bar should be the same as controlling the Peltier temperature, since both variables are proportional to the voltage supplied.

If you want to set the limit to some exact temperature, you will probably need to use a temperature sensor and a limit or kill switch, since the Simple Motor Controller does not have a feedback feature. How you want to trigger that switch (e.g. using a microcontroller) is up to you. However, if you want to set a soft limit, you can use the control center to set the max speed under the motor settings tab, which should effectively limit the temperature.

- Amanda

Hi Amanda again,

i managed to get my setup working with my peltier and cooling fan. the cooling fan (12V, 0.31A) and pololu motor controller are connected in parallel to a 12V, 8.5A power supply while the peltier module (15.4V, 7A) are connected to the OUTB and OUTA ports of the pololu motor controller

however the cooling fan was able to work and the motor controller could be detected by the control center BUT my peltier was not working! I check the peltier and it is new and working when connected separately. Where did it go wrong?

thanks amanda

Hello again.

Can you try setting your motor controller to run the Peltier unit at a 100% duty cycle? Can you post pictures of your setup that show all of your connections?

- Amanda

so basically the setup is as attached in this post

peltier to Vin Vout pins of motor controller

motor controller connected with cooling fan in parallel and both connected to battery in parallel, of course haha

sorry error, i meant peltier connected to OUTA & OUTB pins/ports of motor controller while Vin and Ground ports/pins of motor controller is connected to the circuit board. i shall attach the real schematic here: (live version of circuit diagram previously posted)

hi amanda these are the input settings, motor settings and advanced settings for the pololu upon connection. what needs to be changed?

this is the status printscreen, previous post was on input settings, motor settings and advanced settings. peltier does not seem to work. wonder why…

Thank you for posting a picture of your setup and screen shots of your Simple Motor Control Center. Did you try running your Peltier at 100% duty cycle? If you are unsure how to do that, you could try moving the “Manually set speed” bar to 100% under the “Status” tab, then clicking the “Apply Settings” button.

I did not notice anything obviously wrong with your connections, however, it is generally not a good practice to use a breadboard for high-current connections like driving your 7A Peltier unit. I recommend simplifying your system to just the power supply, Simple Motor Controller, and Peltier device until you get it working.

- Amanda

Thanks amanda its working now! however lets say if i want to use 2 peltiers instead of one, is it advisable to use the same pololu motor controller and pololu software for BOTH peltiers? am i right to say that if i am using 2 peltiers then i need to buy the motor controller that have 6 ports am i right? 4 ports to connect to the 2 peltiers and the other 2 ports for powerr input. thank you!

If you do not need to control them individually, it is possible to control two Peltiers with a single Simple Motor Controller (SMC) by connecting both devices in parallel (e.g. connect one side of each Peltier to OUTA and the other side to OUTB). However, the motor controller needs to be able to supply enough power for both Peltiers, so I would not recommend using the SMC 18v7 that you currently have, since your Peltier devices can draw around 7A per (14A total). Instead you might try using the SMC 18v15 or SMC 18v25, which can output up to 15A and 25A respectively.

If you want individual control over each Peltier, then you are correct about needing a motor controller with two motor channels (4 motor ports + 2 ports for VIN and GND).

By the way, it is generally a good idea to choose a motor controller that can output some margin more than the current draw of your load. At the moment, your setup seems to be fine, but if you start noticing any issues, or you plan on getting another one to use with your second Peltier, you might consider using the SMC 18v15.

- Amanda

Where did you buy your power source from? Are you using a PID code or is it PWM, also are you using the motor controller to reverse the polarity or that switch? Im trying to do the same thing but with 6 peltier tiles


Thanks Amanda for the reply. Could i know lastly, given the picture attachment i posted in this reply, whether 2 V- and 2 V+ ports on the power supply machine in the photo attacahment means that I can use each pair of V+ and V- for each 7A peltier? you mentioned to use the 18V15 controller but i guess for the second peltier i plan to use a DPDT relay switch as mentioned by you several posts ago. Will it be fine in this way? the power supply machine will be able to supply to 2 peltiers am i right? thanks!