useless ebay peltiers

[mindburner]

title should read PELTIERS sorry

I have been trying to build a cooler box, along the lines of Gary Honis's design. The peltier's I have tried just don't do anything. They are useless. The box itself came out fine and I have the insulation foam in place etc. I just can't get any cooling. Tried 50w and 80w ebay specials, both seem pointless. They get cold when initially powered up, but soon loose the cooling. I have tried to improve the heat sink etc but without success. I think they are just very inefficient.

I have used a variety of PSU's, heat sinks etc with little improvement. I am beginning to wonder if I have non conductive aluminum. It's 1mm think and seems a decent grade.

I just wonder has anyone managed to get a solution that worked short of buying a cooler box and removing the unit from it. This maybe the last resort but in the US these coolers are a lot cheaper than ripoff Britain, so I wanted to be sure a cooler would work before splashing the cash.

Anyone got a make or model of a cooler that they hove used to good effect in the DSLR cooler?

many thanks

heres a pic

[pete_l]

Don't forget that air is a pretty good insulator. So it will take a long time for any "cold" to get from the Peltier to the camera. Also, the insulation around the box needs to be pretty good too. I doubt that a token layer of polystyrene tile (I don't know what you've tried, but my attempt was pretty useless, too ) is simply not enough. Even with all the gaps sealed, Poly isn't that great an insulator and I think I'd have needed a few inches of "proper" insulating foam to keep the warmth out.

Afterthought: If you want to test the efficacy of the cooler, build a small insulated box the size of the Peltier and maybe 1cm high that's water-tight and has a removable lid. Slide it onto the Peltier, so the the cooler is the base of the box. Add a known quantity of tap water, cover the top and turn on the Peltier. See how long it takes to freeze.

if you start with 5cc (5grams) of water at room temperature - say 20°C you'll need to supply 420 Joules to get the water to freezing point and another 1670 Joules to get it to freeze. 2090 Joules all told. If your 50Watt Peltier is running at 100% efficientcy (it isn't) and your box lets in no external heat (it won't) then it'll take 42 seconds to freeze the water. In practice it'll take much longer, but by timing it you can calculate the "cooling power" of your Peltier, since you'll know how much energy the water lost in order to freeze (the 2090 Joules) and the time it took to extract that much heat energy from the water. if it took (say) 200 seconds, then you'll know ther cooling power was 2090 / 200 = 10.5 Watts. You may be able to improve the Peltier's cooling power with a larger heatsink or better insulation.

[ncjunk]

I thought polystyrene foam was a good insulator? solid polystyrene isn't so much, but the foam is and widely used as such.

theres a few people on here with peltier experience i'm sure one will be able to help.

[JCJC]

We did find a secondhand campingaz box on the bay, like this and stripped the plastic parts off the lid, used the assembly (almost as it came) in the side of an ali box.

The peltier came fitted with a lump of ali (1 x 3 x 3) against one side, lots of thermal paste and I think we changed the fans, when finished the box/camera/fans/cables were heavy, but worked almost to Gary Honis spec's.

These are at Aldi soon, don't know much about them.

We clad the outside of the box with a few layers of depron underfloor insulation, also used for rc aircraft (flying wings).

I had plans for a MK3 replacing the Ali box with just an 'L' shape, fix camera and cooler, box to be depron - but never quite got there.

Hope this is helpful, we played with ebay peltier's, odd heatsinks and fans at first, the complete assembly was easier and wish we had started with that.

JCJC's dad

[pete_l]

I thought polystyrene foam was a good insulator? solid polystyrene isn't so much, but the foam is and widely used as such.

In bulk, for sure. The box I made was from a single tile and was only about 1cm thick. It didn't really keep anything cold for long (I put some ice cubes in it and they melted about half as quickly as the "control" outside the box). It might just have been too leaky or too thin.

[Gina]

My cold finger Peltier cooler works! I have a 25mm square, 5v 19.5W Peltier on the cold finger and then a copper plate (22swg) and then a 40mm square 12v 50W Peltier. This is water cooled with a NorthBridge water block, plus tubing, reservoir with pump and 120mm square radiator with same size 12v fan. I got -19C on the cold finger but the EXIF T reading was only -9C. I'm currently working on a better design with much shorter cold finger. Both Peltier TECs came from eBay from a UK supplier with top rating. They aren't all that efficient but they do work. I made the mistake earlier of using a too powerful Peltier.

[ncjunk]

In bulk, for sure. The box I made was from a single tile and was only about 1cm thick. It didn't really keep anything cold for long (I put some ice cubes in it and they melted about half as quickly as the "control" outside the box). It might just have been too leaky or too thin.

Ah ok 1cm won't be thick enough, it would be interesting to see how it performs each time you double the thickness. I assume there would be a limit to usefull thickness plus it would look really bad if too thick

[mindburner]

i'm currently on 3cm of insulation. The peltiers don't even seem to drop it 1 degree. I have only had iy on 20mins from a 5 amp PSU, but I thought it should have been cooler.

Thanks for all the info ont he coolers, I iwll check them out.

[Fish-Man]

They are working aren't they ? and you haven't "blown" them.

The cold side should go white and frosty within a couple of minutes, and the hot side, should be too hot to keep your finger on, within a few seconds.

Are you using the correct voltage ? Each size has a different voltage requirement, and using too high a voltage will kill them, and too small a voltage will not get them upto working point.

Your 5A PSU should be fine for the smaller peltiers, but if you are trying the 80W 12v one, your PSU has run out of steam (5A x 12v = 60W)

Just a couple of things to think of..

Regards,

Paul

[mindburner]

They are working aren't they ? and you haven't "blown" them.

The cold side should go white and frosty within a couple of minutes, and the hot side, should be too hot to keep your finger on, within a few seconds.

Are you using the correct voltage ? Each size has a different voltage requirement, and using too high a voltage will kill them, and too small a voltage will not get them upto working point.

Your 5A PSU should be fine for the smaller peltiers, but if you are trying the 80W 12v one, your PSU has run out of steam (5A x 12v = 60W)

Just a couple of things to think of..

Regards,

Paul

Hi yes they get cold when run with a 12 v supply. I dont think they are blown But not cold enough to get frosty. The hot side gets hot but again not overly. I was running the 50 w one off a 12v 1.25a psu then tried a 5a 12 one. Both were poor. I must check the current pull on the 5a supply incase it is not actually supplying 5a but less.

[Gina]

i'm currently on 3cm of insulation. The peltiers don't even seem to drop it 1 degree. I have only had iy on 20mins from a 5 amp PSU, but I thought it should have been cooler.

Thanks for all the info ont he coolers, I iwll check them out.

You seem to have a duff one. They get cold one side and hot the other in a few seconds even on lower power. Are you sure your PSU isn't switching off due to overload? Have you checked the voltage and current going to the Peltier? If you have power going into the device you will get heating even if you don't get cooling. I don't know how they behave when they fail as I haven't had one fail (as yet).

[mindburner]

hi Gina, yes they get warm ok and the cooling is there when first powered up but seems to fade after a few seconds. I will measure the current draw as maybe the laptop type PSU mount supply I have may not be producing enough.

[anon584358564e]

I know this is several years late, but try putting the hot side's heatsink in water. Just drop it in a dish of water that is below the level of the electronics. Make sure you have the silicone sealed kind and not the bare conductor kind or this is an accident waiting to happen.

I had a similar problem where I thought my ebay peltier was useless. When I ran current through it it would cool down a bit at first, then actually climb above ambient temperature on both sides. A few degrees hotter on the cool side and way, way hotter on the hot side. Like 200 degrees F before I shut it down for safety.

It turns out it just wasnt heatsinking very well. Peltiers can only cool between a certain range, like 60 degrees or so. You can find this in your datasheet. If the hot side gets 60 degrees above ambient, the cool side will never drop below ambient no matter how much power you throw at it. I placed the fins of the hot side heatsink in a tupperware dish of water and it instantly fixed everything. The cold side dropped below freezing, which was impressive for a 90 degree day.

Also make sure you are running enough amps through it. Below about 1/3 of its maximum rated amps it wont do any cooling at all, only create heat. Check the amperage with a multimeter to make sure you are getting enough.