# Thermoelectric air cooler and heater controlled by a thermostat

#### Mohammed Yassine

Joined Apr 13, 2016
5
Hello everyone !

I am currently working a thermometric air cooler and heater that can be controlled by a thermostat for a college contest. I am quite gifted when it comes to finding hardware solutions to specific problems; However, I am really novice when it comes to electronics and my country's maker community is currently ignoring me and not taking me seriously. I came here looking for help if it's possible. The air cooler and heater uses 4 TEC modules and needs to be controlled by a thermostat. I am really looking for any help I can get my hands on as the contest is drawing near; Circuit board, hints.. anything. There is a fab lab where I live so I have access to 3D printers, CNC machines and prototyping machines. Thank you so much in advance.

#### Mohammed Yassine

Joined Apr 13, 2016
5
Apparently I can't edit anymore but I just wanted to say that the circuit consists of 4 TEC modules and 2 fans and a thermostat or at least a button for heating and a button for cooling.

#### wayneh

Joined Sep 9, 2010
17,168
Do you have a question? I have two for you: What are you planning to use to power this thing? In cooler mode, where do plan to send the heat?

You didn't ask for my opinion, but I think a thermostat-controlled TEC is not going to win a college-level contest.

#### tcmtech

Joined Nov 4, 2013
2,867
You didn't ask for my opinion, but I think a thermostat-controlled TEC is not going to win a college-level contest.
Oh you might be surprised/appalled at what can win a college level contest these days.

Depending on how he implements it I think it's well worth following through. Using it as a simple solid-state active heat pump to keep a small room cooler and dryer by pumping heat and moisture to the outside is not that unreasonable of concept.

It may not have the efficiency of a phase change mechanical heat pump system but it would be something that could be make very light weight and thus highly portable.

I know if I was stuck in an office or some room with marginal if any air conditioning a small briefcase sized window mountable air conditioner that puts out just enough cool dry air to keep me comfortable in a chair in front of it would be a very attractive device!

#### wayneh

Joined Sep 9, 2010
17,168
I don't disagree but I suspect that not all of the thermodynamics have been considered for this project. It will take some engineering just to remove more heat than the waste heat from the power supply.

#### tcmtech

Joined Nov 4, 2013
2,867
I don't disagree but I suspect that not all of the thermodynamics have been considered for this project. It will take some engineering just to remove more heat than the waste heat from the power supply.

Us a number of lower wattage TEC units in series until they reach a combined working voltage acceptable level to run on rectified line voltage (ten to Twelve 12 volt 100 watt units in series will run on 120 VAC rectified without issue) and put a heatsink and fan on the hot side that can handle 3 - 4X the thermal transfer as the cold side units.

Granted the efficiency won't be all that great but when if you could have simple portable single person air conditioning in a package the size of a common briefcase that no more complicated than set in a window and plug in the trade off for many would be well worth it!

From what I can see online a ~ 3000 BTU cooling capacity (~1000 input watt) prototype unit with heatsinks and fans could easily be manufactured for around $120 US currency. Thread Starter #### Mohammed Yassine Joined Apr 13, 2016 5 Do you have a question? I have two for you: What are you planning to use to power this thing? In cooler mode, where do plan to send the heat? You didn't ask for my opinion, but I think a thermostat-controlled TEC is not going to win a college-level contest. Four TEC modules TEC 1-12706 57.2W 15.2V 6A, and two fans; Powering on a 220V/50 HZ network. Whether cooling or heating is selected, the waste heat will be blown out of the room. Thread Starter #### Mohammed Yassine Joined Apr 13, 2016 5 So I have been looking around and tinkering and I have made this. Note: I am very novice when it comes to electronics so it maybe something very absurd Note also that the thermostat and power supply will most like be bought and not made. What do you guys think ? Will it work ? what can be adjusted ? Thank you so much in advance ! #### Attachments • 7.8 KB Views: 9 #### wayneh Joined Sep 9, 2010 17,168 Sure it will work. Just be sure the power supply has a rating comfortably above the total current you need. Don't forget the fans and any indicator lights and such you might include. You might place the power supply to be cooled by the device itself. In heating mode, you won't need to reject heat outside the room. These things usually include some refinements such as a delayed turn-off of the fans and a temperature sensor on the hot side of the TEC to shut everything down if it overheats. A fan failure is not uncommon, and you don't want to burn up your TEC because a$5 fan failed. At a minimum, you should think about using fuses.

A common mistake with these projects is using too small a heat sink on the hot side. It needs to shed up to ~10X as much heat as the cold side draws in. The performance of the entire machine can be limited by the ability to remove heat from the hot side.

#### tcmtech

Joined Nov 4, 2013
2,867
What do you guys think ? Will it work ? what can be adjusted ? Thank you so much in advance !

Well as I mentioned earlier by putting the TEC units in series you can add their voltages up to a point where line voltages can be used and the step-down power supply not needed which saves you money on parts plus using several smaller lower wattage TEC cost less than a single larger one of equal capacity.

The rest is just a matter of properly sizing your heatsinks and fans to work most effectively with the ambient temperatures.

#### wayneh

Joined Sep 9, 2010
17,168
Ummm.... transformer-less power supplies are kind of verboten around here.

#### Mohammed Yassine

Joined Apr 13, 2016
5
Omg guys I can't thank you enough ... Thank you guys so so much !

#### tcmtech

Joined Nov 4, 2013
2,867
Ummm.... transformer-less power supplies are kind of verboten around here.
Sort of yes but also not really. Apparently if it uses a capacitive coupling to produce a lower than stock line voltage ist forbidden but if it directly rectifies the line voltage and then either uses that line level DC or then run that through a SMPS or PWM control of some sort like a treadmill motor or such uses it's good to go.

I'm suggesting direct conversion of the AC line to DC and using that so it should be fine here.

But then again who knows? Maybe running multiple TEC units in series directly at line voltages is a forbidden thing as well?

#### KeepItSimpleStupid

Joined Mar 4, 2014
5,088
I have done a TEC cooling application for an enclosure. No controls except a variable power supply. They are not efficient by a long shot.