Peltier Electronic Project Help

[Ben227]

Hi there, I am a complete beginner to electronics and my overall knowledge is very limited so bear with me.

I wish to power a peltier module and two fans using one power supply and have the circuit activated using a relay controlled by an Arduino Uno.
The peltier I have taken out of an old mini fridge is a TEC1-12705. Will this Peltier module be "powerful" enough to be used as a drinks cooler? Should I buy a different one?
The two fans run at DC 12V 0.19A.
So I want a power supply to power the Peltier and two fans. My problem is that I don't completely understand Amperage so I don't know what to buy or whether it would be able to power all of these components.
If somebody could give me a suggestion to how to power this project and suggest a specific power supply it would be greatly appreciated.
Thanks
Ben

 

[davenn]

hi Ben
welcome to the forums

The datasheet says that it will draw 5 Amps at its 12V supply
If it was running for reasonable periods of time, several hours at a time, I would be getting a PSU capable of 6 - 7 Amps
so that it wouldn't be working at its limit

Dave

 

[(*steve*)]

(edit: thanks Dave for looking up the actual current consumption -- my figures updated)

There are a few issues:

1. The peltier device will require the largest amount of current -- you need to determine what that is (was it a 12V fridge?)
2. If you have a 12V supply, you simply add up all the currents. Say the peltier is 5A, the fans 0.2A each, and your assorted other electronics 0.1A. This means 5.5A are required. To be safe you might choose a power supply capable of 8A.
3. You want to avoid placing the peltier device under cycles of thermal stress if at all possible (See point #19 on this page).

This document provides some useful generic information.

Another useful point of view is expressed here. The recommendation is that (especially for cooling applications) a variable voltage (essentially a variable current due to the load curve of these devices) is better than PWM as it results in lower I²R losses and thus higher efficiency. This is of course predicated on your ability to vary the voltage without associated losses that would result from a linear regulator. So a variable output switchmode regulator is probably the ideal solution.

Given that you "don't understand amperage", much of the previous discussion may be well over your head, but it may be useful to come back to as you learn more and more.

If the peltier is designed for 12V then you can simply connect it straight up to 12V and get maximum cooling (or heating) and go for your life. Given the relatively low thermal conductivity of air, it may be best to line your "fridge" with aluminium sheet that is connected to the cold side of the peltier device so as to maximise the reansmission of heat to the peltier and then out to the outside environment.

 

[Ben227]

Thank you very much guy you have been very helpful.

So each component will draw what ever amperage they need from the power supply?

So you recommend 12V 8A. Will this voltage and amperage be safe to breadboard?
Thanks
Ben

 

[Harald Kapp]

The voltage is safe, 12V are no problem for a breadboard.

8A can't be handled by a typical breadboard (if you think of the solderless plug-in type). You should consider using prototyping PCBs (veroboard , stripboard or similar). Even with this kind of prototyping board you may have to "reinforce" the traces carrying the 8A. This is easily done by e.g. soldering an additional wire onto the tracks that carrry high current.

 

[davenn]

Thank you very much guy you have been very helpful.

So each component will draw what ever amperage they need from the power supply?

So you recommend 12V 8A. Will this voltage and amperage be safe to breadboard?
Thanks
Ben

Yes ... they only draw what they need ( wont go into the true technicalities till you are ready )

Yup, 12V 8A would truly be sufficient
as Harald said, no, breadboards wont handle that current ( note you wont be drawing 8 Amps ... refer to what I said in earlier post about having a PSU rated higher than what is needed so it isn't overworked)

personally I wouldn't put more than ~ 0.5 Amp into the solderless breadboards

Dave

 

[Ben227]

The voltage is safe, 12V are no problem for a breadboard.

8A can't be handled by a typical breadboard (if you think of the solderless plug-in type). You should consider using prototyping PCBs (veroboard , stripboard or similar). Even with this kind of prototyping board you may have to "reinforce" the traces carrying the 8A. This is easily done by e.g. soldering an additional wire onto the tracks that carrry high current.

Is this an appropriate prototyping board provided I reinforce the tracks?
http://www.amazon.co.uk/gp/aw/d/B00...251b88a1&pi=SY200_QL40&qid=1410536403&sr=8-3#
Bit of a silly question, but is 12v 8amps enough to give a significant electric shock?

 

[Gryd3]

Bit of a silly question, but is 12v 8amps enough to give a significant electric shock?

Don't play with your circuit with wet hands.
Your body from hand to hand dry should be more than 1700Ω which will not allow anymore than 6 or 7 mA DC to travel through your body. This is not a significant shock and the value rated is a rare value for the human body to be at. (5% population has a low skin resistance such as this) Remember though that smaller currents can be lethal if they are from AC, or delivered directly or in close proximity to your heart.
That said, it is never a good idea to intentionally pass current of any sort through your body. Disconnect power from your circuit before working on it, or use safe practices and never grab a conductive item with each hand. It is a good practice when working on higher voltages to work with one hand in your pocket.

http://en.wikipedia.org/wiki/Electric_shock#Body_resistance

 

[Ben227]

In regards to the extra wires I will add to the veroboard/stripboard, do the wires need to be a certain thickness or can I use any type of wire?

 

[Harald Kapp]

Here's a table that tells you which wire gauge to use for what current. It has entries for 7A and 9A (chassis wiring) with AWG 22 or 21 respectively.

 

[Ben227]

Okay, I have bought and had delivered a 12v 8A power supply, however when I connect my peltier to the supply with a fan also, the fan stop and starts consistently every second as does the LED indicator on the power supply. This is not the case when I connect the fan by itself. Any help?

 

[Gryd3]

Okay, I have bought and had delivered a 12v 8A power supply, however when I connect my peltier to the supply with a fan also, the fan stop and starts consistently every second as does the LED indicator on the power supply. This is not the case when I connect the fan by itself. Any help?

sounds like an overload condition to me. Check your wiring, and are you sure 8A is suitable for all of the devices connected?

Edit: 8A was recommended, but perhaps the model for the peltier device was mis-printed or typed out incorrectly. It could also be bad or damaged.... ultimately, there is a problem somewhere that we can help locate.

 

[Ben227]

sounds like an overload condition to me. Check your wiring, and are you sure 8A is suitable for all of the devices connected?

Edit: 8A was recommended, but perhaps the model for the peltier device was mis-printed or typed out incorrectly. It could also be bad or damaged.... ultimately, there is a problem somewhere that we can help locate.

Do you think it would be easier to just order a new peltier module, say a 12v 5a one off ebay? As the one I have has been taken out of a fairly old mini fridge so may not be reliable or as you say may not be suitable.

 

[Gryd3]

Do you think it would be easier to just order a new peltier module, say a 12v 5a one off ebay? As the one I have has been taken out of a fairly old mini fridge so may not be reliable or as you say may not be suitable.

This may resolve the issues, only if it is the peltier device.
The other parts should be looked at and tested before you invest more money into it.
do you have any other 12V sources you can try? (ie. old computer power supply)

 

[morphingstar]

Anyone knows the efficiency of Peltiers these days? They used to be in the <10% region. Lots of wasted energy.

 

[Ben227]

This may resolve the issues, only if it is the peltier device.
The other parts should be looked at and tested before you invest more money into it.
do you have any other 12V sources you can try? (ie. old computer power supply)

The fan works perfectly by itself running off the power supply, is that not evidence enough that it is the peltier causing the problems?

 

[(*steve*)]

The fan works perfectly by itself running off the power supply, is that not evidence enough that it is the peltier causing the problems?

It could be the power supply not able to handle the load. If the load is within the stated capacity of the PSU, then it's not the peltier's fault.

 

[Ben227]

I bought another peltier module 12V 5a, I hooked it up to the power supply and placed it with the right end in the heat sync and fan cooling. With the new peltier there was now jumping or stop and starting with the power supply and everything worked smoothly. However, I believe I have broke this module, as after a minute or so testing with it powered it stopped cooling on one side and began to overheat all over. I presume I will need to buy yet another one. Can anybody help me with what went wrong? Was it not getting cooled enough by the fan? Do I need to hook it up to a resistor or something?

 

[Ben227]

I've sorted out the Peltier heat issues, what I am wondering now is if I can run the Peltier 12V 5a, the two fans 12V 0.19a, an arduino uno which is powering a relay board, and a set of LED striplights 12V 2a, all off the 12V 8a Powersupply. Excluding the Arduino this adds up to 7.38a required, and the arduino is recommended to have 500ma to 1a power, which means it would be using the power supply to its maximum output of amperage, would this work theoretically or will the power supply not be able to handle the load? I could use a different power supply for the LED striplights, but having two power supplies would be a pain.

 

[Gryd3]

I've sorted out the Peltier heat issues, what I am wondering now is if I can run the Peltier 12V 5a, the two fans 12V 0.19a, an arduino uno which is powering a relay board, and a set of LED striplights 12V 2a, all off the 12V 8a Powersupply. Excluding the Arduino this adds up to 7.38a required, and the arduino is recommended to have 500ma to 1a power, which means it would be using the power supply to its maximum output of amperage, would this work theoretically or will the power supply not be able to handle the load? I could use a different power supply for the LED striplights, but having two power supplies would be a pain.

You are reaching the limit, supplies are usually over-engineered to allow a little overhead.
Running it like this could make it susceptible to voltage dips, or even having it cutout.
I can't tell you if it would work or not. In a pinch, I'd do it, but to make sure it continues to run smoothly you may need to invest in a larger supply, or an additional supply.