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Thermoelectric cooling system

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asha

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Hi everyone,

I need to design an electronic circuit for a thermoelectric cooling system, which has to be a closed-loop control system, an idea where to find a good references ?

Thanx
 
You will need a temperature controller with a current controlled output. Try googling "proportional temperature controller" , "pid temperature controller" or "thermoelectric temperature control" for references.
 
Hi everyone,

I need to design an electronic circuit for a thermoelectric cooling system, which has to be a closed-loop control system, an idea where to find a good references ?

Thanx

This is pretty straightforward. You can use a proportional integral controller, thermistor (or thermocouple) for temperature sensing and a TEC driver. The TEC driver circuit needs to be an H-bridge for bidirectional control, and it can be either a linear or PWM mode, but PWM is more efficient. You can directly drive the TEC with the PWM pulses and you don't need a coil unless you want to use one for other reasons (such as electrical noise and component stress). The PWM frequency should be > 2 kHz and preferably > 10 kHz to not stress the TEC. The PI controller can be either from a microcontroller or a simple OP-Amp circuit.

It's really not very difficult, but there are many options on the actual implementation. The final choices depend on your constraints. The typical modern approach is to use a thermistor with an analog circuit to sense the temperature. Then feed this into a micro with A/D conversion. Generate PI control and PWM signals with the micro and drive the H-bridge with TEC. Then you need to tune the proportional gain and integral gain to get a good stable closed loop control.
 
Lol...I happen to be doing this soon..But steves PWM advice is poor. TEC do not like PWM. They prefer full on, full off. The thermal inertia of the load will govern the on/off times. all u need is a set point. PID control is only necessary if there is low inertia which is unlikely unless u are working with very small load volumes, eg. chemicals or bio samples.
U do need a thermistor as a sensor though, driving the MCU ADC which u calibrate with a thermocouple DVM or other temp. indicator.
 
I also had a bad experience with PWM but have later found out it is ok as long as you don't exceed the voltage rating of the device. ie don't drive a 12 volt device with a 50% PWM from 24 volts.
 
Ejaz
Tell us what you are doing so we can get it right.
What TEC, what are you cooling, what voltage do you have, how good must your temperature control be.
 
But steves PWM advice is poor. TEC do not like PWM. They prefer full on, full off.
PWM is full on, full off. It's just the speed that varies.;)
 
Sir presently iam using Silicon drift detector(SDD) for which i want to cool for -30degrees centegrate...
Iam reaching upto 20 degrees and getting much noise in output of FET used to pass current in SDD. So what can i do for better performance. Can u suggest me any circuit or design for TEC?
 
can anyone suggest me a FET which can give output ID as 5A

Can anyone suggest me a FET number which has a capability of giving 5A as Id
 
U can get to -20 if u insulate it properly. A modern TEC would give u a 50 degree C differential using optimum conditions and optimum currents with optimum cooling.
U will need a sizable heatsink and cooling fan, or perhaps a PC water cooling rig to ensure the -30 deg C. Only possible if TEC hot side is kept under 20deg C, otherwise u will have to stack TECs which is more complicated.

However, does your SSD generate any wattage load?
It seems u want -30 deg C or better. This won't require any 'control' just insulation, heatsinking & a continuous regulated powersupply....at near the 15VDC rated of the TEC.

here's a nice logic level beefy FET for u:
VISHAY SILICONIX
IRLZ44PBF

Should run 5A without needing a big heatsink
 
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I don't know much/anything about SSD's but I think there is only a small amplifier to create heat so it is like Mosaic says.
Maybe you could post a picture of your set up? If you tell us the TEC it might help.
With what we know now the only suggestion I might make is that you could liquid cool the hot side. Maybe a compressor type freezer to cool some liquid that you circulate thru the heatsink to lower the hot side temperature by 10 or 20 C.
Maybe we can help with some more info. What is your hot side temperature for example. How are you insulated? I think it can be done.
 
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