Easy way to power many pelts without expensive power supply.
 

The biggest problemwith pelts is obviously the cost and effecieny of the power supply. Now, since peltiers are very simple loads and care very little about the quality of the power coming to them, why not hook 10x 12 volt pelts or 5x 24 volt up in series, thus making a 120 VDC peltier. Then simply take 2 or 3 large bridge rectifiers hook them to the 120 VAC line, then hook the peltiers to the other side. This would cost very little and provides loads of peltier cooling. It is also very small. The only problem I can forsee is that you would be saying "wtf am i supposed to do with 5 or 10 pelts?". Also 120 VDC is very dangerous as it is not a self quenching arc. Any suggestions/thoughts to my idea?

The easiest application I can see is a water cooler.

Unfortunately the AC ripple would destroy the TECs fairly rapidly, and a capacitor to smooth 120v @ 10amps (need like 200miliF) would cost more than a dedicated smps. The beauty of smps is the frequency is many kHz rather than 60Hz, which makes the capacitors (and transformers) much smaller, and therefore cheaper, at the smaller cost of some beefy fets...

]JR[

Actually 40000uF might do, although a 6000uF capacitor with a high enough voltage rating is £100/$160, and you would need 7 of them!

]JR[

Can Pelts even work off AC current?

I don;t know much about the specs of them but arn't they made up of diodes?

An LED is a type of Diode and that won't work if installed the wrong way wrong round and I'm prepared to bet they won;t work off AC.

Won't you have simmilar problems with an AC current though them

Boli, if you look at the first post, there's a mention of a "bridge rectifier".

A bridge rectifier is a set of 4 power diodes that turn the negative voltage of an AC wave into a positive one. If you've seen a sine wave, try to picture it, with the part that's under zero reversed to be positive, resulting in what looks like a mountain range. ;)

Then, as ]JR[ correctly pointed, what you have left is a voltage that goes up and down, from (near) zero, up to 170+ volts (on a 110 Vac outlet), which is not unlike a switched signal. So to smooth out the curve, we add capacitors, which get charged at the wave's peak, and discharge at the wave's low point, to result in an almost flat DC output. TECs live longer with a true DC output.

Limitations are described accurately by ]JR[.

Re: Easy way to power many pelts without expensive power supply.
 

You need to remember that 120V is rated in RMS values. When rectified to DC its more like 170VDC with massive ripple. That, combined with the huge amperage you'll pull... It's just not feasable.

The electric company would be giving you kisses though...:dome:

well, good to hear, wasnt aware pelts cared about ripple and all. O well. It would be a good idea if the caps needed werent so expensive. Looking around, I have a 1500 VDC cap thats huge, and is only 4 mfd, and a 2500 VDC cap that ginormous and is only 10mfd.

It's easy to greatly reduce the ripple problem to the point where a much smaller cap can deal with it.

Just have the power company install 120V 3 Phase power. Wire the incoming 3 Phase to an outlet near your computer. Then use three bridge rectifiers.

Now you're ready to power your massive array of pelts. :p

Or just throw the tecs away and get a giagantic 3phase hvac compressor and build a phase change 5stage cascade that runs on nitrogen :) Permenant ln2 temps for the same price electricity wise as your hooge tec array :)

And yes ripple is a killer on tecs cooling wise aswell, i was experimenting with some 10000uF caps on my homebuilt psu and with 0uF smoothing the temps were like 15degrees higher than with 50000uF worth

]JR[

I thought of this a few years ago. You'd be the only private citizen invited to every major event the electricty company had.

LOL!!!

i especially like "only private citizen" one!

for a 12 volt supply, what voltage rating should my caps be?

how about fuel cell technology?
wj

As long as it goes "VROUM!" and 0 to 60 in less than 5 seconds, OK! ;)

I use a quantum-singularity watercooler in an antigravity-powered containment cell to sink all that CPU heat into a dimensional rift.

n00b.

Alchemy

Ill see if i can find a link, some guy has done it (The 5stage cascade), although its probably got a 3hr pull down time :)

]JR[

16 volt minimum but I would use 25 or 50 VDC myself, depending on what's available.

Kool... :)

What size flux-capacitors do you use to stabalize the temporal distortion fields?

assuming i could get hold of the capacitors to make this work:
in the uk we have 230vrms 50hz ac power so running 20 220w tecs on rectified and smoothed mains each would have 11.5v and draw about 19amps so in total the system would be 230v 19a
230x19= 4370 or 4.370 Kw or 4.370 units of electricty per hour so 38281.2 units per year @ 5.45p per unit. total cost £2086 per year or $3000. but for that you would have 2600w of cooilng which, if used with 2 tecs on the cpu and the rest on the water chiller, should keep the cpu well below zero.:D bit expensive compared to phase change though.

Why don't you just add a transformer to the circuit. This would cut the voltage down to whatever you wanted and isolate the system, somewhat. It would also draw far less current. 19A is alot going through 1 outlet.

Have you ever seen those solid state lab or aquarium chillers? Bender from ocforums has a few of those and they run 10 50watt peltiers in series off 120vdc, and as far as I know, the power supply for it isnt much. Next time I see him on IRC, Ill ask him about it.

now that I think about it, My motor on my mill runs 100vdc and draws 4.5 amps. and the box is tiny that controlls everything, Ill have to take a pic of it sometime.

Jon

90 or 180VDC motor controllers will NOT work for powering pelts!

The motor controllers do not care about ripple, and most of them are pulse width modulation (PWM) anyway. Which will burn up a pelt fairly quickly, as has been said.

The PS inside one of the Thermotek 25x series chillers is a smps that puts out 65vdc @ 7+A. The pelt assy is made of 10 pelts in series running at about half voltage.

I have NEVER seen a manufacturers specs sheet that indicated pwm was a bad thing for controlling peltier power, rather over the past few years I have seen recommendations from some that say they are okay as long as they are designed to work within some frequency (which I forget at the moment) range.
So, if you can post a link (from any peltier manufacturer) that would indicate that pwm is bad, I would appreciate it.
wj

> As long as it goes "VROUM!" and 0 to 60 in less than 5 seconds, OK!

http://www.nytimes.com/2003/09/19/au...es/19ELEC.html

How about in 3.7s ? ;) .

are you refering to this?
http://forums.procooling.com/vbb/sho...&threadid=4327

and since I was already here:

TECHNICAL DESCRIPTION
Power to the thermoelectric module is delivered via a 400 Hz Pulse-Width-Modulated (PWM) output. This methodology will not reduce the thermoelectric module's reliability due to thermal cycling (as can some other on-off controllers).

http://www.tetech.com/temp/tc24-10.shtml

this is the typical information I have gathered here and there,

so once again, let's see some recommendation against pwm from the peltier manufacturers or........quit spreading the misinformation.
wj