Peltier based aquarium cooler/heater?

Awesome. The peltier I'm looking at draws up to 10A. Are there any h-bridge IC's that can handle that kind of draw?

Ok seems I have a lot to read about h-bridges. If anyone can give me some pointers that would be great. Thanks.

http://forum.arduino.cc/index.php?topic=169717.msg1262798#msg1262798

Plan B ~ Plan F.

There are lots of high current H-bridges advertised on eBay - search for VNH5019 or BTS7960. Or use this one Pololu - VNH5019 Motor Driver Carrier from Pololu.

Great, thanks again. I've looked at these h-bridge chips available on ebay and BTS7960 looks the cheapest (£12 from China). It's a little more than I was expecting to pay (about the cost of 4 peltiers!) -- before I order, is there a cheaper DIY approach or should I just take the plunge and get this?

Also, will I need an opto-coupler or similar to protect the arduino? Or is that taken care of? Thanks.

With the BTS7960 rated at 43A I guess up to 4 peltiers (10A each) can be connected.

I was looking at power supply units for such a project and it seems a DIY AC->DC will be needed. I had no problem finding bridge rectifiers rated for 50A, but where does one find 50A transformers (240v AC to 12v DC)?

The cheap DIY approach would be to use 1 or 2 relays. Preferably a DPDT relay to reverse the polarity of the drive to the H-bridge and a single mosfet to turn the power on/off (and do PWM if you want to). That way, you can use the mosfet to turn the current off before switching the relay over, to avoid arcing. But if you don't want to PWM the Peltier, then two SPST automotive relays with >10A DC contact ratings would be sufficient. You'd need to use transistors to drive the relays.

You don't need optical isolation if you use a common ground between the Arduino power supply and the Peltier power supply.

Combo:
With the BTS7960 rated at 43A I guess up to 4 peltiers (10A each) can be connected.

I wouldn't push units purchased via eBay too close to their maximum ratings. OTOH the BTS7960 drivers I found on eBay are all dual units, so you could run e.g. 2 or perhaps 3 Peltiers from each channel.

Combo:
I was looking at power supply units for such a project and it seems a DIY AC->DC will be needed. I had no problem finding bridge rectifiers rated for 50A, but where does one find 50A transformers (240v AC to 12v DC)?

Don't do that, buy a switch mode power supply instead. Search your local distributor for a suitable one. If you intend to use more than one Peltier, consider connecting 2 identical ones in series, because 24V 10A is easier to manage than 12V 20A.

Thanks this really helps. I have an old PC power supply unit which can provide 450w via 12v and 5v rails. Would that be a suitable? Are PC PSU's switch mode power supplies?

Combo:
Thanks this really helps. I have an old PC power supply unit which can provide 450w via 12v and 5v rails. Would that be a suitable? Are PC PSU's switch mode power supplies?

Yes they are. Check the current ratings of the individual outputs, which are usually written on the unit. You will probably find that the +12V output can't supply as much as 10A.

How much heating/cooling power do you think you really need?

Boiling the ocean?

The PSU says input 200-240v / 4.5A.

Output: +5V 22A max
+5V(FP) 2A max
+12VA 18A MAX

Combined power on +3.3v and +5v rails not exceed 150w
Combined power on +12va and +12vb rails not exceed 360w.
Max continuous dc output power shall not exceed 375w.

Ok so it's 375w. Does this seem ok? It would be convenient to power both the arduino and peltier(s) from a single power source...

To start with I'd like to power one peltier but I'm thinking this could probably power two of them? I'd be happy to use more to get a faster temperature ramp (they're cheap).

Combo:
With the BTS7960 rated at 43A I guess up to 4 peltiers (10A each) can be connected.

I was looking at power supply units for such a project and it seems a DIY AC->DC will be needed. I had no problem finding bridge rectifiers rated for 50A, but where does one find 50A transformers (240v AC to 12v DC)?

They're available but cost a pretty penny. Here is a 120V to 12V@600W(50A):

afremont:
They're available but cost a pretty penny. Here is a 120V to 12V@600W(50A):
http://www.amazon.com/Tiella-Lighting-800AT600T-Remote-Transformer/dp/B007JY3U66

Ouch, yes. Salvaging an old PSU so much more economical (assuming I can get it to switch on, been trying for a couple of hours now jumping various wires, etc).

Combo:

afremont:
They're available but cost a pretty penny. Here is a 120V to 12V@600W(50A):
http://www.amazon.com/Tiella-Lighting-800AT600T-Remote-Transformer/dp/B007JY3U66

Ouch, yes. Salvaging an old PSU so much more economical (assuming I can get it to switch on, been trying for a couple of hours now jumping various wires, etc).

Connect the green wire to one of the black wires, and it will turn on (assuming it's an standard ATX)

In some cases the PC power-supplies need a minimum load on the 5V output, but it's not often that it's an issue.

// Per.

Thanks for the help. I was wondering if these BTS7960B (or similar components capable of reversing a motor) will supply the peltier with PWM or with pure DC? I've read that PWM for peltier is not ideal.

Combo:
Thanks for the help. I was wondering if these BTS7960B (or similar components capable of reversing a motor) will supply the peltier with PWM or with pure DC? I've read that PWM for peltier is not ideal.

They can supply the unit with a fixed DC voltage in either direction, or they can be used to PWM the element. See item 41 at http://www.tellurex.com/technology/peltier-faq.php regarding PWM and Peltier elements. It's true that if you want to use PWM to run the Peltier element at less than full power, then this is not as efficient as running it off steady DC at a lower voltage, unless you use a series inductor to smooth out the PWM.

Hello,
I was looking for the same project as I also need to cool a small size (25 l) aquarium to a constant 26-27 deg. c. and I would like to use a Peltier based solution + temperature ontrol loop based on Arduino.
Please let me know in case you completed the project.

Combo:

afremont:
They're available but cost a pretty penny. Here is a 120V to 12V@600W(50A):
http://www.amazon.com/Tiella-Lighting-800AT600T-Remote-Transformer/dp/B007JY3U66

Ouch, yes. Salvaging an old PSU so much more economical (assuming I can get it to switch on, been trying for a couple of hours now jumping various wires, etc).

Momentary contact the green output wire to any black (ground) output wire.

Henry_Best:
Momentary contact the green output wire to any black (ground) output wire.

If you're only making the contact momentarily, the power supply turns off again. There are absolutely no "smarts" in the power supply that will keep it turned on. The green wire needs to be pulled down to GND potential to keep the power supply turned on.

In a PC, the Chipset has the control over this signal.

// Per.