I'm trying to build an aquarium chiller using a Peltier device, large computer heat sink, and a laptop power supply to drive the system. I'm using this device:
http://auspicious-e.com/index.php?main_page=product_info&cPath=30&products_id=263
The stats say it has a 1.3 to 1.5 Ohms resistance.
The laptop power supply I'm using outputs 20V and 3.5A.
I first tried a 12V 1A wall wart to run the device. This worked, but got the wall wart very hot (as expected) and couldn't drive the cooler to full power.
I tried just hooking the laptop power supply to the peltier device and the power supply would just cut out. It obviously has a short circuit protection and was detecting way to many amps drawn.
My calcs would tell me that at 20V into 1.5 Ohms of resistance I'd have 20/1.5 Amps (ohm's law, right?). So that's way over the rated 3.5A. So I went and picked up some Radio Shack resistors. They are 10Ohm 10W ceramic resistors. So my idea was that I put all 3 in parallel. So that gives me 10/3 = 3.3 Ohms of combined resistance. I then put this in series with the peltier device. So that would give me 3.3 + 1.5 = 4.8 Ohms of resistance total, right? So that should draw 4.2A. Still over the rated limit, but it works to not trigger the protection circuit in the power supply.
PROBLEMS:
1) The resistors get really hot. My IR temp probe is reading 230F even when they are connected to a heat sink.
2) The peltier is not transferring much more heat than with the 12V, 1A supply. My guess is that all my extra power is going to heating up the resistors....
Any ideas on how I can power the peltier properly??
http://auspicious-e.com/index.php?main_page=product_info&cPath=30&products_id=263
The stats say it has a 1.3 to 1.5 Ohms resistance.
The laptop power supply I'm using outputs 20V and 3.5A.
I first tried a 12V 1A wall wart to run the device. This worked, but got the wall wart very hot (as expected) and couldn't drive the cooler to full power.
I tried just hooking the laptop power supply to the peltier device and the power supply would just cut out. It obviously has a short circuit protection and was detecting way to many amps drawn.
My calcs would tell me that at 20V into 1.5 Ohms of resistance I'd have 20/1.5 Amps (ohm's law, right?). So that's way over the rated 3.5A. So I went and picked up some Radio Shack resistors. They are 10Ohm 10W ceramic resistors. So my idea was that I put all 3 in parallel. So that gives me 10/3 = 3.3 Ohms of combined resistance. I then put this in series with the peltier device. So that would give me 3.3 + 1.5 = 4.8 Ohms of resistance total, right? So that should draw 4.2A. Still over the rated limit, but it works to not trigger the protection circuit in the power supply.
PROBLEMS:
1) The resistors get really hot. My IR temp probe is reading 230F even when they are connected to a heat sink.
2) The peltier is not transferring much more heat than with the 12V, 1A supply. My guess is that all my extra power is going to heating up the resistors....
Any ideas on how I can power the peltier properly??