Meanwell S-240-24 240 Watt Power Supply
 

Hey guys..

I just bought a Meanwell S-240-24 240 Watt Power Supply. It runs on 24V. I got it cheap, therefore that is why I didn't get the 12V one. I need this to run a 172W pelt specd for 12V and 11.6 amp.
Here is the problem.. I am not an electronic guy, and this may have been a foolhardy purchase however, I need to convert this to power my 12V. Unless you think my tec could handle 24?? Any suggestions?

Not sure where to post this, as I didn't see a power mod category.

Re: Meanwell S-240-24 240 Watt Power Supply
 

Something doesn't make sense here. You said, "I need this to run a 172W pelt specd for 12V and 11.6 amp."

Got a link? It doesn't make sense that the TEC has the following specs:

Qmax = 172 W
Vmax = 12 V
Imax = 11.6 A

172 Watt Tec specs from Danger Den:

Qmax = 172 W
Vmax = 24.6 V
Imax = 11.3 A
dTmax = 69 °C

HAHAHAHAHHA!!! I was shooting from the hip. I DID buy that exat pelt, but since I am electric illiterate to the 1000th degree and I was going of memory i missed the mark.

Ok. I stand corrected now.

Can I.. should i do it? Will I be ok? I was wondering if you could run the thing on that 24V or the 12V line. I don't wanna burn up the pelt. Any suggestions are welcome. I was told that it could run on a 12V and I assumed that it should.

the suggestion to be more accurate with my numbers is implied. :D

You'll want to run it at about 85% capacity, otherwise it just sucks up power like you can't imagine, and it's just not worth it.

Yes, you can run it at 12v, and it will perform ok, but only for a chiller, not for a CPU pelt.

So if I just plug right in to that 24V im good to go!

How would I get that to run at 85 capacity? Somehow put 19.2V on it?

You could put a 0.5 Ohm 50 Watt resistor in series with the TEC.

That would give you about the right voltage. The resistor would be dissipating 40 Watts though, and would need a substantial heatsink.

Wouldnt that resistor be tiny? And dissipating that much heat..hmmm.. place it on the load side. Any way to work it into the internals of the case and lower the entire line?
Bah.. I have no idea why these things psu's cost so much.
Sorry to ask so many questions, but I have never taken an electrical theory or any class related.. time to take that at summer school or something.
With that much heat in question, running it strait out at 24V could be an even par tradeoff? Powerconsumption vs. Heat?

Yeah somehow I don't see using a resistor to "use up" 5volts as being a particular power saver but then - I didn't so well on that circuitry midterm -stupid AC current, I never understood you -Although I didn't think my DC was that bad :P

Or does the pelt run "better" at 85% or just better in the cooling:power use ratio?(Which is what I thought BigBen was implying)

I understand that for that last 15% you gain minimal cooling and it chuggs double the power.

Actually depending on your hotside cooling system, you may lose CPU cooling as you take the TEC voltage above 80% of Vmax.

TEC power consumption goes up roughly as the square of the voltage, while the TEC has already reached about 90% of it's cooling capacity at 80% of Vmax.

The added temperature differential you can get across the TEC by taking the voltage above 80% of Vmax, is generally offset by the increase in hotside temperature due to the extra heat the hotside cooling system must remove.

Putting a resistor in series isn't an efficient way of reducing the voltage to the TEC, but at least the power dissipation in the resistor doesn't have to be cooled by the TEC's hotside cooling system. An additional heatsink in some existing airflow path can do the job.

A better way to go, would be to put a high efficiency adjustable DC to DC converter between the PSU and the TEC and adjust it to the voltage that gives optimum cooling, but I'm not going to explain how to do that here.

Do you mean one of these? (link)
If anyone can find a cheap one.. ill be greatful. No price on these.. >:(

Here's a better idea: sell the Meanwell for a profit, and get yourself something else ;) Don't they sell (new) for ~$100?

Those are high power linear regulators. They won't be any more efficient than a series resistor.

I don't think it would be easy to find a cheap DC to DC converter that puts out the 18 - 19 volts that would be ideal. I really think the series resistor is probably the most practical way for you to use that supply.

Resistor Link

These are available from Digi-Key. Digi-Key part # TMC50-.50-ND is a 0.5 Ohm 50 Watt resistor. They cost $5.21 each.

But what else is he going to get?

A couple PSU's could be used with +5V of one in series with +12V of the other to get 17V, but that's a lot of space taken up to do the job.

18 to 19 volts is just not a commonly used voltage.