The usefullness of a compact, cheep, clean, controlable and non-consumable source of heat extraction is well understood. I have read an untold number of posts speculating on the many uses of Peltier cooling devices for clandestined chemistry. No doubt many bee's have tried using Peltiers, but I doubt many have actually been able to use one in production. Let me know if you found different, but I found the little bastards to be somewhat of a tease the first half dozen times I tried to get them to do any real work.
They would initially produce an impressive burst of temperature drop, shooting to 50-60 deg C below ambient, but quickly drift back up and in some cases come to rest ABOVE ambient. Since a cooling device that works for less than a minuite is near useless, I kept trying and scraping idea's that involved peltiers until I learned 'the secret' to using peltiers.
'The secret' is simply the realization that these devices have inherent tendancy towards currrent stability. They will draw far more current, and thereby deliver more heat to the 'hot' side, than can be removed by the heat exchanger attached to the device. If offered mucho amps, they will pass mucho amps and happily fry themselves like a vietnamese monk.
Circuits are available to limit current at the supply, but without inteligent current controll based on actual sensor feedback, pessamistic assumptions must be made which will seriously limit the practicality of the device. Since it is doubtfull that your average bee can look at a heat exchanger and guess its Watt transfer capabilities(which actually requires calculating the exchange metrics for two coupled heat exchange processes that start at ambient conditions and then cycle towards an equilibrium), limits can save the device from self destruction but are unlikely to produce an optimal result.
And since no feedback it provided to the operator as to the result being achieved or the final resulting temp, the operator has no idea what is being achieved, how much more could be achieved or what to do to make that happen.
Inteligent control based on sensor input can change all this. By sampling temperature data from the hot and cold sides of the device, or even better, the coolant entry and exit temp from the hot and cold sides of the device, the actual results can be calculated using the maximum ejection capabilities of the liquid/air heat exchanger as the limiting factor.
In addition to providing a maximized result based on the limitations of the current system, the control software can provide feedback to the operator about how much of the pumping capabilities of the chip are being utilized and what can be done to improve the situation.
I have already done about half of what I describe using a cheep and easy to use microcontroller called an OOPIC. The OOPICE has numerous built it A/D converters and offeres easy current control through built in PWM(pulse width modulation) functionality. PWM is the technique of toggeling the current on and off at a high frequency and varying the percentage of on-time vs. off-time to control the current provided to the device. This is the recomended method for controlling a Peltier.
The OOPIC dev kit with everything necessary to program it, except for a windows PC, can be purchased for less than $100. It connects to the PC via a serial cable that is supplied. You program the device using your choice of; a simplified VB like syntax, a simplified C like syntax or a simplified Java like syntax. once simplified, all three look almost alike anyway. The main difference being whether you put a semicolon at the end of the lines and how you punctuate a function call.
If you are a first time programmer, you will have to make all the first time programmer mistakes, but you are not likely to find a less demanding environment to learn in than this. Getting a temp reading takes a couple lines of code, setting the PWM percentage takes a single line of code. The entire program with all the bells and whistles will likely be less than fifty to seventy lines of code unless someone gets inspired enough to add a complicated LCD or HTML realtime display screen.
Now is the time to make suggestions, if people have other controllers they like. I also have the Rabbit 2000, which is much faster and has a more professional development environment. But the dev kit is $200-500 with a limited use compiler that will likely need to be upgraded, and does not have built in A/D conversion. So an A/D chip, mux and voltage reference circuite would need to be added, which is a pain in the ass compared to the OOPIC. It also requires classic C programming skills, further reducing its usefullness.
Let me know what you think...
TrickE
And on the eight day, God created Meth...
... and hasn't done much of anything usefull since!