Unless you expect to bounce between Hot and Cold a lot I would start out with a Relay. Its simple and will require almost no troubleshooting.
Thinking about Peltier coolers that i have worked with, a few things come to mind.
- They've have always been 4A + whatever the fan requires.
- of the top of my head the maximum temperature change is 18 degrees Celsius.
Don't pin me down on these things though.
With super slow PWM (.05Hz a 20second cycle) i think you can come to a very decent prediction of what might happen, though i suggest to just leave the Fan running.
The delay in temperature change is going to depend a lot on the object the is being cooled/heated, so i think that a percentage controlled system is definitely worth a go,
First of all, why did you start a new thread ? and why didn't you leave a link to the new one in the old one ? I don't think it's very cool really.
I mentioned the 'very slow PWM' which i still think is the way to go,.
F provide it with a lower voltage, the current will drop and the heat exchange will be less, but for that you need a variable power supply, or device that can increase resistance, like a transistor.
But i do really want an answer to the first question.
You have a good point in Your reply.
I once PWM:ed a 48 volt fan. It could not be done the seller told. But what the hack I thought. Take the picture: Using loose cables in Your hand and You shortly make contact.. The fan makes a little rush, whatever type it is.
Done. I selected a very low frequency, maybe 25 Hz. Then I applied PWM in duty cycles of 0, 25, 50, 75 and 100%. It worked like a charm.
I've only played with a Peltier module a few years ago but I recall one issue is the difference between cooling and losses.
Cooling is a function of average current. Losses are a function of the RMS current.
So if you have 12V and you need the cooling a 6V supply would generate....
Cooling approx = to that with 6V.
Losses will be Ploss = V^2/R so during the 12V period the losses are 4 times that of 6v. And because a 50% dutycycle the losses are down to 2 times that of a 6 volt supply.
Because Peltier's are so inefficient I would think extra losses are not desirable.
Note there may be other reasons not to PWM a Peltier I don't know. I'm not a good source for Peltier operation except for the above.
Hi there. Can I control the power or not with PWM pulses? I have a battery and I don't want it to drain so fast. That is, I want to use less power from the peltier cell while controlling it with PWM. If I have it at 50% it consumes 50% less from the battery than what it consumes if it is at 100%.
I read that no, and also that yes and I am already confused.
I have an other question. What I want is that my peltier cell does not consume so much so that the battery does not discharge quickly.
What happens if I lower the voltage? It would consume less Wh and if I am not mistaken it will make the battery not discharge as fast.
It's possible? That is, use 6v instead of 12v so that it consumes half.
Yes you can. It is somewhat less efficient than using DC.
That is, use 6v instead of 12v so that it consumes half
It will consume about 1/4 the power (P = V^2/R). Batteries are not the preferred power source for Peltier devices.
Can you tell me more about that? Please why do you say less efficient? If I feed it with DC and control it with PWM, wouldn't it be the same?
Why not? I am looking for it to be a portable system.
Of course not. PWM is rapid on/off switching. That cannot possibly be considered the same as DC.
Why not? I am looking for it to be a portable system
Fine, but be prepared to carry around large, heavy batteries. Do some experimentation, and you will learn.
I think the best solution is to just vary the voltage. What do you think? That is, reduce and increase the voltage if I want it more or less cold or hot.
Those batteries commonly used for drones are small, light and powerful (18000 mAh at 14.8V is about 20000 mAh at 12V). If I lower the voltage more, it will last longer because of the lower consumption, right?
I have not tested the batteries yet, on paper everything is beautiful. But, before buying the batteries (the most expensive) I would like to have other opinions.
I used to have a 100AH battery (lead-acid deep cycle, thick plates, not VMF) and a Peltier cooler. By switching it on and off every few hours i could make the food last through the festival weekend.
If efficiency is a motivation, drop the whole idea of a Peltier element. They are hugely inefficient.
The Peltier metallic diodes are all in series and their individual break-down voltages usually add up to the rated voltage for the device.
You might try experimenting with a Peltier device sometime. They run as expected on lower than the rated voltage. They are not "diodes", and are fully reversible.
My first Arduino project. but only on-off control
Useful Peltier application and test note here: https://www.ti.com/lit/an/slua979a/slua979a.pdf