peltier usage

[ving (David)]

during winter i could take 10 second exposures with my lpi with minimal hot pixels... now the weather is warming i am struggling with 2 second exposures!

i had never looked into cooling with peltiers before today and was browsing jaycar and noticed they are only about $10. I have a suitable fan and heatsink already so what else would i need? is this a hard project to do? (i have absolutely no electronics ability) anyone here done this before? how effective is it? i only have a 9v battery for the RA drive on teh mount... how would i power it?

thanks in advance for input/comments

[bojan]

You will have to do serious redesign of your camera, if you want to cool the CCD chip only... Which I think is the better option. (see my design here http://www.iceinspace.com.au/forum/a...4&d=1156235900)
If you want to cool the whole thing... well simply build the temp isolated enclosure for your camera (fridge... the cooling plate should be inside as well) and apply the fan to stirr the air inside. It may work...

[ving (David)]

hmm... a camera re design is prabably going too far.

[bojan]

Those peltiers are usually designed for 12V (for car fridges).
All you need to really take care about is to mount the hot side on the proper heat sink (preferably cooled with fan, to prevent damahe to the peltier module. This must be outside of the enclosure of course). Inside enclosure goes the cold plate, mounted on the cold side of the peltier, with your camera & fan.

[ving (David)]

just wondering, how much voltage does a usb 1.0 port put out? is usb 2 different?

[bird (Anthony Wesley)]

Peltiers chew lots of current. My cooler with 3 of the jaycar peltiers in parallel uses about 10 amps @ 12v when running.

This is way past the ability of usb or firewire to supply :-)

cheers, Bird

[ving (David)]

bugger, thanks sir

[asimov (John)]

12V car battery with charger attached coming up David? Or do you have another plan of attack?

[bird (Anthony Wesley)]

If you're close to 240v power you can't beat a computer power supply. lots of amps at +12v, and they're cheap.

cheers, Bird

[asimov (John)]

I have been running mine on a 240V - 13.8V 6A supply. Works well.

[monoxide]

my first post here!, anyway,
id be careful with peltiers,
i have had a fair bit of experience with them (computer cooling)
most that i have seen are 15v 20a units (they are more efficient at around 12.5 however) its best to get a dedicated power supply for them or you will find the wiring getting hot to the touch, melting then frying the power supply and possibly whatever you were trying to cool in the first place.
meanwell make the best peltier power supplies.
keep in mind the heat generated by the peltier unit, air cooling a peltier is usually really inefficient. heat generated = the wattage of the peltier + the wattage of whatever your cooling, then you have the worry of condensation unless you fabricate a peltier controller (or buy one) and for the cost of getting all that going you could just put a larger heatsink on it or a fan that pushes more air. or even watercool it.

[Gargoyle_Steve (Steve)]

The trouble with peltiers is that if you just apply voltage and leave them running they work flat out at maximum amps / cooling. You could end up freezing your cam depending on what size peltier you use (often rated in eiter amps drawn, r watts consumed). Remember that these things are basically a heat pump - give it max power, it keeps pumping heat at max capability.

Better applications usually have some form of control that limits power drain (and maximum heat pumping) by either modulating the duty cycle (ie power switches on and off rapidly so it is effectively only on 40%, 60%, etc of the overall time) or by thermostat (temperature sensor) to switch the unit off when desired temp has been reached.

Dock Smith have a kit for an electric motor variable speed controller used for drills, etc this is a "duty cycle" control type design, can be used for peltier control.