portable mini fridge and lasers

[eyceage]

Why not ... run the TEC at its rated power and amperage to take advantage of it's cooling potential?

Well, unless you're generating an awful amount of heat, at full power you risk condensation or even ice crystals forming on lasers and such.

I use a bench-top linear power supply to run mine, and dial-in the right voltage so it's cool but without condensation.

If I turn it all the way up, it will pull moisture out of the air which freezes on contact - forming pretty crystal ice trees and mossy looking structures.

[MechEng3]

My thermocouple is mounted on the bottom of the laser ,right on the 1/2" aluminum plate that the units are mounted on. The TEC is on the opposing side. When the plate temp gets to any point above 26 C , the PID does it's job. When it cycles to keep the plate at this temp, I have no worries of ice in or on my lasers. It is an extra measure to keep them cooler than just a big plate. I feel it does an excellent job of safely controlling temps and keeping the blue photon factory from premature death. So my TEC unit is not just "on" all the time. It has a controller to take any faults out of the loop here....even a falure warning of under/over temp.....my setting of choice. So far it has a stable record of +/_ 2 deg C of target temp.....

[eyceage]

ahhh... ok. so the PID automatically does what I've been doing manually. Cool (no pun intended)

Where do you get such a thing? Are they easy to set up?

[MechEng3]

Auber instruments has a very nice unit. User friendly as well as small in size. I found the ones I have on fleabay...the guy is in Florida if I remember. Has a selection of thermocouples as well. Good units as I have seen them on other equipment. This is the same as the ones I have....... http://cgi.ebay.com/Universal-Digita...QQcmdZViewItem It is a bit on the bulky side but I reccomend a new Solid State Relay {opto coupled} for the task at hand. I have some pix in my gallery under tec cooling and new setup.

[LaserLover]

ive just been given a mini fridge for free and ive just taken it to bits.

It seems perfect for keeping my scanner cool, all it is, is a peltier, heat sink and fan on a big metal plate.

anyone else tried this???

I don't see any reasons to cool your scanner unless the heatsink the're mounted on are inadequate to dissipate the heat generated under long extended operating periods.
I can see you potentially using your peltier cooler to experiment on lowering the operating temperature of laser diodes to shorten the operating wavelength. Also to cool the Laserver blue 473nM DPSS laser head because the heatsinks they provide don't provide adequate cooling. Just be carefull to control the temp accurately so you don't run into condensation problems and you might boost the power by up to one third and enjoy longer operating lifetime as well.
Get a good TEC temp controller. Mecheng can fill yoi in.
Rick

[BADGER]

Why not just use a controller >PID< and run the TEC at its rated power and amperage to take advantage of it's cooling potential? You already have the heat sink in hand. It should handle the watts of heat generated by the TEC it was on if a good fan is used. I have a program here somewhere to calculate heat dissapation on a given surface area for Watt/amp TEC and shows amount of cooling needed in cfm's and size of minimum heat sink required.

proportional integral derivative controllers are'nt very well suited to peltier modules due to the fact they generaly give a pulsed output. which isnt what you want, really you want a variable voltage. eyceage has got the right idea. a varibale resistor inline would do the job.

[MechEng3]

It works really well for me as it has been tested for quite some time now with a SSR. The biggie here is to set the proportional time value a little larger than you might think.This will slow down the gain response. Set the integration time values high so that response is also slowed,making the output more stable.The differentiation time will be set in according to supplied chart functions, in deg C so that your local upper and lower limits can be anticipated and compensated for without the system oscillating.The dampening function should be experimented with to get a medium setting being carefull not to set too small....oscillation again. If your unit has digital filtering here again a middle of the road setting will adjust for the best delay time of response. The SSR [solid state relay] doesn't mind being signalled the way I have it set up. These settings keep on/off time to a .5 second cycle with my unit. It manages to keep the 1/2" aluminum plate and lasers at a very stable 28 deg C no matter where it is working as far as local temps are concerned. I just wanted more than a cooling device that was on or off. I wanted control of it and to be able to see what it was doing. Thats all. Just another system to add into the cabinet that I liked.

[yaddatrance]

This is the same as the ones I have....... http://cgi.ebay.com/Universal-Digita...QQcmdZViewItem It is a bit on the bulky side but I reccomend a new Solid State Relay {opto coupled} for the task at hand.

Good find! That looks aethetically nicer and definitely cheaper than the TEC
controllers I've been using! Have you had a chance to monitor it to see how
it performs? I think I'm going to pick one up this weekend. I figure at that
cost I can't lose

[The_Doctor]

That's was on my watch list for a while, so I didn't forget it. I want one, but for now, it will have to wait, like most things..
The dual display ones are even nicer.