Electronics Help

[TrevorW]

I've a Peltier that's designed to draw 12v 4amp to operate at 48watts roughly however under load the temperature control circuit I'm using only draws 10.2v, so I assume the Peltier isn't operating at peak efficiency as wouldn't be drawing 4amp.

Any advice would be welcome ???

[wasyoungonce (Brendan)]

12V 4amp is alot ...are you sure your PSU is capable of supplying 12V at that amperage.

You said it only draws 10.2V? The peltier won't draw that voltage it will draw a current, aka around 4amps at "12V supplied".... This is indicating the PSU you are using is "loading down" and not capable of supplying 12V at 4 amps.

I suspect the peltier is a 48W device thus if you provide 20V it should draw around (p=EI thus I =P/E thus I = 48/20 = 2.4amps). You can vary the E and I proportionally to each other but it will still be a 48Watt device. Thus you original PSU is probably not up to the task.

Do you have another high amperage 12V PSU?

Maybe try the peltier on a car battery! Do you have a 10amp multimeter to measure the I draw?

[Starkler (Geoff)]

Edited: Oops nevermind. Didnt read the original post properly

[Garyh]

Hi Trev,
I did notice that temp regulator at Oatley outputs 10v to the peltier module, The only way you could up the voltage is alter the curcuit somehow to up the voltage. Maybe a resistor value with the voltage regulator? I don`t know enough about these things to be of much help.

Also just check the PS like mentioned to make sure there is the capacity to supply the full load. Im ditching my old PS (ATX pc supply) as it can`t handle the load (total of 5-1/2amp) even thou it says 14amp @ 12v , and drops to only 9.3v with full load. My new ATX supply handles the load nicely with only a .3v drop.
cheers

[TrevorW]

Tested the connectors without load and states over 12v once load applied drops to 10.2v.

Power supply says its 12v 5 amp maybe should try a different power supply.

Maybe it's something to do with the temp controllers attached are details of this.

Cheers

[wasyoungonce (Brendan)]

That controller kit can be set up in 2 ways:

1. A continuously switching controller. It is constantly switching the power on/off (in a duty cycle), according to the temp of the peltier. Thus the measured voltage at the peltier may be lass than the full supply as it is being switched rapidly.

2. As a temp switch. Aka it switches on and of to maintain temp.

I suspect you have it set up as in 1 and that nothing is wrong. Best you try the peltier (alone not with the controller cct) across a car battery as this will have ample supply to test it.

[Karls48 (Karl)]

Trevor, the Peltier temperature regulator kit you got, regulates current to the Peltier by switching it rapidly on and off. That’s why you are measuring lower voltage on output. As the temperature reaches preset point, the time space between on and off period increase thus reducing average output voltage and current to about 0.35A. By using this controller the Peltier device is never fully on or fully off. Using simple thermostat on and off controller is not recommended with Peltier devices.

[TrevorW]

Would it be better just running it without a controller and having it on all the time

[wasyoungonce (Brendan)]

There is no problem running the controller with the peltier, it will run slightly under peak efficiency. But, you can adjust the temperature you want to keep the peltier at your desired "peak" temp.

Alternately if you want max cold just run the peltier without the controller.

Tis a trade off as they say.

[TrevorW]

Thanks for the input, I found to get the lowest temp I had to keep the pot trimmed up so the fan on the heatsink was running all the time. I'm probably better off going without the controller as the aim is to get the Peltier as cold as possible and keep it there as the cold plate is's open too the air so thermal loss would be signifcantly more than an enclosed container where insulation would help maintain a constant thermal state. Although even when connected to the power supply and pilling a full 12v after 15 odd minutes of running the temp on the cold plate still only gets down to about 1-2 C so it could be the power supply

Cheers