Fridge TEC

[rog8811]

I had a search around and found only 1 mention of fridge TEC's in the last year so........

As I cannot walk past a skip without having a look (dumpster diving in the US?)
I came across a mini 240v~ 12v DC fridge...... misses out the "what I did next" bit.....

I have a 2" square TEC on a 6" square, finned, heatsink. I connected it up to 1.5v (drawing 400ma) and it works!
Has anyone used one of these at all? Is 1.5v the max I should feed it with? I cannot believe that they will take 12v.

Any info gratefully received.

Regards rog8811

 

[Benm]

Most TECs are designed to operate up to 12 or 15 volts, provided you can suplly both hot and cold sinking to sustain such a thermal transfer rate. That would mean a setup with fins on both the hot and cold side to make a fridge, and possible a fan to assist.

But if you want to use it to cool a laser: leave the fins on the hot side and find out how much voltage it requires to cool your laser down as low as you want it to. The problem usually is condensation and even ice formation, not lack of TEC power.

 

[rog8811]

The problem usually is condensation and even ice formation

I got as far as condensation when I tried it out, thanks for the info that it should take more volts if required.

Regards rog8811

 

[likewhat]

With those big ones you can run like 15 volts and 5 amps through them. If you are going to use it to keep a laser cool you should set up some kind of a thermostat that keeps it from getting so cold it creates condensation.

 

[rog8811]

Oops, took the thermostats off ...easy to put on again though , thanks for that.

Regards rog8811

 

[IgorT]

I have a fridge like that, and i sometimes use it to cool lasers down.


But i also have some very small Peltiers - 20x20mm and 15x15mm - and even these take up to 4A, but at very low voltages (1.9-2.5V). 400mA is nothing for a Peltier.

I have a few datasheets, and will look up the current requirements and heat pump capabilities for a 50x50mm, like you found. It will not be the exact current yours can take, but it should give you an idea.

A quicker way would be to simply hook up the fridge power supply to a (running) car battery and measure the current going through the peltier. Don't use AC tho.



BTW: I just got some samples of very efficient (buck circuit) constant temperature Peltier controller ICs. Unfortunatelly i won't be able to play with them untill the middle of the next month (too much work). There are also some other simple constant temperature Peltier regulator circuits available online for various purposes. Need to search for the links.

 

[rog8811]

hook up the fridge power supply to a (running) car battery

I did my surgery in the dark beside the skip.... the rest went back in  :
I will look forward to any info you can find.

Regards rog8811

 

[Heidi]

I have a small fridge that runs on mains and 12v too. Never used it as I go camping a lot and have a big cooler box that uses either ice or 12v battery/transformer. The small fridge is no use to me as I can't get a bottle of wine in it.  :-*

Still collecting bits to make my first burning dvd laser, and was hoping to use the TEC from the fridge to cool 2 open can 20x dvd burner diodes + maybe use one of the beam splitter cubes to combine the outputs from two diodes. I'm really hoping I'll get close to 500mw if I drive them hard and keep them nice and cool.

I'm hoping to solve the condensation problem by sealing the diodes in a airtight box and using those bags of silica crystals you get with camera packaging to suck up any moisture that may still linger after the enclosure is sealed.

Does anyone know how to remove the beam splitter cubes from the dvd writer assembly? They seemed to be glued in with something. How can I remove it without damaging the optical surfaces of the cube?

 

[likewhat]

For temperature regulation you can probably just use a sensor that turns on and off a relay. If you just want to keep it from getting hot that is all you need.

I have built diode lasers that needed a high degree of regulation in the past so we used a simple yet effective analog circuit that monitored the temperature compared it with a set point and varied the current going to the TEC with a FET. They would keep the temperature constant to within 10 mK of the set point. I

 

[rog8811]

Does anyone know how to remove the beam splitter cubes from the dvd writer assembly?

On the blue ray sleds you can just use a scalpel to take out the splitter cubes, they are not held very securely.... only trouble is they are very small and hard to work with without touching the surfaces.

For most of my combining I have left them in the sled housing, which I cut bits off, to allow me to mount the lasers in the right place.

Regards rog8811

 

[IgorT]

Ok, i found info on the following Peltier sizes:

- 50 x 50 x 4.5mm   15.4V   8A   79.1W heat pumping capability
- 49.5 x 49.5 x 3.9mm   15.4V 14A 123.5W heat pumping capability

Hmm, i didn't expect this... The smaller one is actually more powerfull. I guess you could still hook it up directly to a car battery and measure the current, to get a better idea, to which one of the above it is closer.

Of course you will never need even a fraction of this power. You only need it to pump away around 1W of heat, depending on the diode used.
It would take a constant current source and some fine tuning, untill the temperature doesn't drop or climb anymore.

Or if you put together a circuit with a thermistor, you could just set it to any desired temperature, and the circuit would do the rest, no matter what the amount of power dissipation is required...

Using thermostats is usually not recommended for Peltiers from most manufacturers, but it still works. The manufacturers recommend PWM or current regulation.

It's very late here, so i'll post the links to those circuits tomorrow.

 

[rog8811]

Thanks all for the information, I will have a play when I get a bit of time.

Regards rog8811