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Author Topic: Peltier via PWM  (Read 1800 times)
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Hello!!
I've never used Peltier cells and I'd like to build up a closed loop controller using Arduino and a Motor Shield. The controller must be able to drive the Peltier in both ways (cooling and heating).
For the programming part I'm ok (I'm more a programming guy than an electronic one).

My problem comes to the power circuit connected to the Peltier, I will use a 37.9W cell (max 3.9A or 15.7V), my idea is to connect the peltier to the two outputs of a H-Bridge (like the one found on almost all motor shields) driven by a PWM signal generated from the Arduino. How can i set the current that flows inside the peltier? I mean in a standard mosfet circuit I would use a resistor that fixes the current flowing inside the cells, but in this case?
I would like to use a standard 20euros shields (rated 2A) and not a 50euros one (rated 15A), but I should fix the current to 1.8A more or less to avoid H-Bridge burning every 10 minutes.
Any help is welcome and much appreciated.
Bye



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Limiting the current through a Peltier device will severely limit the cooling ability of the device. You would be better off using relays to turn the device on and off (2 relays with at least 3 poles so you can interconnect them so they can't turn them both on at the same time.

Simple temperature control would be to set the limits for On/Off of the device just turn it on when it needs more heat/cool and turn it off when it is cold/hot enough. You could get better control with less overshot if you worked on PID control. Depends on the needs of the system.

You want to use the Peltier devices at full rated current/voltage to get the best performance. And remember - they only have about a 40 degree F or 22 degree C temperature differential.
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The simplest way of limiting the current is to control the voltage.
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So to run the Peltier at full power, you need an H-bridge capable of supplying 15.7V to it, and the H-bridge must be able to carry 3.9A comfortably. At that current, I'd look for a mosfet H-bridge.
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I've also read somewhere that PWM isn't ideal with Peltiers - perhaps it increases thermal stresses or isn't as thermodynamically efficient as linear drive.  Adding a suitable series inductance to the device could be a solution - suggest doing a little research about how important this is.
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So to run the Peltier at full power, you need an H-bridge capable of supplying 15.7V to it, and the H-bridge must be able to carry 3.9A comfortably. At that current, I'd look for a mosfet H-bridge.

Or Relays. 2 relays would let you select Heat or Cool and could also be wired to interlock so you can't turn both of them on at the same time
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