I've tried to learn as much as possible from existing threads regarding this subject, but I'm left with questions & would really appreciate advice..
I wish to turn on two TEC's and the liquid cooling system (pump, fans etc) that cools the hot side of the TEC's. It will not have to adjust/modulate the temperature either, just turn on/off and run at peak efficiency of the TEC's for set on/off periods (8 hrs on per day).
I would also like to run a few sensors (i.e. hot side temperature) that Arduino can use to safely shut off the system incase a temperature threshold is exceeded on the hot side of the TEC when a pump or fan fails. I will also eventually wish to run a single stepper motor in this prototype.
My concern is choosing the correct components to make this work safely. I've read threads of people using the following (motor) driver shields to connect the TEC's to Arduino. - While their use seems to include modulating the power at which the TEC's run, I only wish to switch them on/off;
Am using 2x 40mm TEC 8.5 Imax 15.5 Vmax
Questions:
Is the driver shield /w MOSFET above the correct and optimal method to do what I want, and which shield is best? (Options outside of the two above mentioned shields are welcome)
If yes, how to choose the correct MOSFET for the current you wish to drive to your TEC? (Read some safety concerns about this)
Which Arduino model would be most suitable for this project and can handle what i've outlined above?
Do I need a switching power supply for this, or will the driver shield run the TEC's at my specified voltage?
Recommendations for temperature sensors, shield etc for intended use v. welcome
Your question needs to be clarified, I think. I didn't get a good understanding of what you want to do.
Are you trying to do bidirectional control (HOT AND COLD) or just hot or cold?
If you are only hot OR cold, do not bother with an H-bridge, use a discrete mosfet probably an N-mosfet low-side control.
If you have say "12V" power supply, and you only want to deliver "5V" to your TEC, be mindful that is quite inefficient to PWM from high to low voltage a TEC. It will be OK but it is not effective for maxinum cooling. You greater greater losses with a 50% PWM of 12V than 100% 6V DC.
Kinnishian:
Your question needs to be clarified, I think.
Sorry, to clarify; Cooling only, and it does not have to increase or decrease with the ambient temperature of the room(The only heat load), as that will remain constant. Do I still need PWM control then?
Unit only has to turn on for 8 hour sessions and cool at peak efficiency. This includes switching on the TEC's, the pump & fans (used to liquid cool the hot side), and ideally sensors whose data can be used to do a safety shut-off in case of pump/fan failure.
What kind of driver shield would I need for the (N-)MOSFET you referred to? As I mentioned the 40mm TEC's i'm using are specified at 8.5 Imax and 15.5 Vmax.
Which Arduino model would be best for what I want to do?
TECs can be put in series, but then you need twice the usual power supply voltage of 12 V (so about 24 V) at about 6 amperes.
If you use them in parallel, you need a 12 V supply capable of at the very least twice the typical current of about 6 amperes (so about 12 amperes).
I assumed you would wire up the latter and recommended a 12 V, 15 ampere power supply for a margin of safety.
The series connection is safer because when in parallel, one of the TECs may take more than its share of the current and possibly overheat. To avoid that problem for parallel connections, each TEC should have its own controller.
jremington:
To avoid that problem for parallel connections, each TEC should have its own controller.
Sorry if i'm completely misunderstanding, but according to the description it's a dual driver shield featuring two channels each capable of delivering continuous 12 A. - Wouldn't that imply that I connect one TEC per channel?
jremington:
Correct. In that case, each TEC would have its own controller.
Two logic level MOSFETs would do the same job, at less than 1/10 the price.
Thank you kindly. -- That makes sense, although I would much rather use the shield now and experiment later (i'm quite inexperienced) since the TEC's are easily the most critical part in the build, and the shield has some built in safety features.
There's a few more components I could use input on, please bear with me
Regarding Pololu shield: are MOSFET's onboard or do you need to add them?
TEC hot side liquid cooling: Would I need another type of shield to control the watercooling pump and the two fans via Arduino? (on/off)
Originally I was considering using a bimetal switch to shut off the TEC's incase of overheating, but with Arduino it seems I could wire a temperature sensor so that Arduino can act based on it's data and perform a safety shutdown if necessary; -- Any recommendations for shield/sensor that can do this?
Lastly, any suggestions/advice in specifying the power supply? I see the Meanwell switching psu's come up often, is there anything better for prototyping and learning?
Would also be useful to know if I would need a lot of output channels on the psu to run to each shield/device
jremington:
What does the Pololu product page tell you?
Sorry, you're right.
jremington:
3. For safety, never rely on electronics when a simple thermal switch will do.
OK, am a bit lost how this would be wired to work together with the Arduino. Would you wire a single bimetallic switch in between the the Pololu shield outputs and the TEC's to shut both off?
I'm also looking at how the bimetallic switches are installed, the way the liquid plates sandwich the TEC's seems to prevent proper installation of the switch near enough the hot-side. Not sure if there is any alternative ways to do this.
