- Apr 21, 2001
Would it be smart to overpower a 15.8 volt peltier with a 17 volt supply? Also, how can you figure out how many amps a line is making?
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LimeyGreg (May 14, 2001 07:29 p.m.):
A peltier needs to be run at the correct voltage for it to work at it's most efficient. If you under voltage it then it will not draw the correct current and so will not cool as it is designed.
Similarly, if you overvolt it it will not be functioning at it's most efficient point and will in fact be producing excess heat so reducing the amount of heat being pumped from the cold plate.
Might I also take this time to point out that a power supply that is incapable of supplying the necessary current at the specified voltage will also lead to reduced output voltage. When too much current is drawn from an underrated supply the supply will only provide it's rated power. Simple power/voltage/current calculations will show this to be true.
Finally, for all those that may think a 300 watt computer psu will power a 150 watt peltier. The rated power of the 12v rail is not 300 watts, it is only a portion. Also, you need to allow about 30% minimum safety margin. Also, be sure that the power consumption you are looking at is the total power and not just the amount pumped from the cold side, otherwise you will end up buying a power supply that will be seriously underated.
LimeyGreg (May 15, 2001 08:46 a.m.):
If that is a stand alone psu then yes it should do just fine. You can assume that the peltier will probably need about twice the power quoted due to it's efficiency (or lack of). Say your pelt consumes 2x54 watts, your current requirement at 15v will be approx 7 amps.
If it's a computer psu then check the current rating of the rail you are using and find it's power output for that output line. Bear in mind that if you run it at the 12v supplied by a computer psu the heat pumped will be considerably less, and if you try using it on an AMD with air cooling you will probably end up with cpu temps greater than just the HSF alone.
What cpu and method of cooling will you be using ?
LimeyGreg (May 16, 2001 02:19 p.m.):
Okay, well you are going to have to either extend your present hold-down device or change it completely. It will depend on your type of chip, is it Slot 1 or FCPGA ?
Your best results will be realized if you make the cold plate from copper, it needs to be larger than the peltier but smaller than the HSF. For optimum cooling the peltier needs to be mounted with 150~300 psi clamping pressure depending on the device. You obviously can't achieve this with the 370 socket tabs, so drill and countersink the cold plate and drill/tap the HSF accordingly - now you can clamp the peltier to the HSF with the cold plate.
There are many different hold down designs and a search the web will yield several ideas. You may not to want to go to the trouble of mounting the cold plate in the above manner but an adjustable clamp is your best option, preferably with spring tensioned screws that will prevent overtightening.
Don't forget the insulation, closed cell neoprene (an old mouse pad ), dielectric silicone grease (automotive tune up grease) for the socket and conformal silicone RTV (more runny than regular silicone) for the back of the socket.
Is your peltier "potted", if not you may want to seal it around the edges to keep out condensation. The main problem here is the material used, if you use regular silicone RTV it usually gives off acetic acid fumes which when trapped in the peltier can cause long term corrosion. A good hi temp epoxy such as say JB Weld may be a better option. There are medical grade RTV's that do not give off acetic acid, but they are not as easily obtained, here is one such company http://www.nusil.com/
I hope that gives you a basis for your installation.
It_The_Cow (May 17, 2001 03:36 p.m.):
I plan on getting a FROST-74 from Tedist.com. It has an Imax of 6.1 amps, Qmax of 65.0 watts, and a Vmax of 16.7 volts, and a DeltaT of 74. And about the volts, it was supposed to be 16.7 volts contrary to my previous statement of 15.8 volts. Sorry