Where you buy yer pelts from?

[Joe]

I am shopping around for pelts , and am interested in where you guys get yers.

I am looking for some 80 - 155watt 12v Pelts.


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C-ya
Joe - Owner/Editor
www.ProCooling.com
Where the Completely Addicted Come to Cool Off

Somebody set up us the bomb.

[eTiMaGo]

ooh there's a whole bunch of places... good one is www.tedist.com

[Cablepro]

I"m looking too...I want a pelt that will run 120W at 12V, so i'm assuming it'll prolly be rated as 155@15V...tedist.com doesn't show any wattage ratings on them that i can see...

[Joe]

I picked up a 130watt ( @15v) at RadioShack for 29$.

------------------
C-ya
Joe - Owner/Editor
www.ProCooling.com
Where the Completely Addicted Come to Cool Off

Somebody set up us the bomb.

[Cablepro]

do they have anything higher? at 12V, that's only 104W...I need something around 120W at 12V...the only other alternative is to get the Drift.8, and run a 24 vdc psu @5.4amps...but i'd rather keep the money in my pocket

[Xeon]

under the standard section tedist has a 156w pelt (at 15.8) so that gives you 118.4w at 12v, and 12.3 amps, they sell it potted for $35, the specs for all the tedist pelts are under their specifications section

overclocker's hideout also sells one that is 156w at 14v, but they dont seem to give you any other specs on it other than amperage, however that would be 134w at 12v

[Rich W]

Grrr.... I've seen this everywhere, and I don't know why it keeps circulating. You can't just say "oh, its MaxQ is x watts at y volts, and so using Ohm's law must be ax watts at ay volts."... the thermal properties of peltier junctions are NOT (repeat... they are NOT) linear... they are indeed quadratic.

[Xeon]

thats whaat i thought, considering it is most efficcent at 75% or 80%, but then yesterday i read an article at tweakmax that said you can divide voltage your supplying by vmax and then mutiply that by qmax to get your correct qmax

[Cablepro]

RichW, please help me with some information...I bought a peltier that has specs: Qmax 172W, Vmax 24.6V, Imax 11.3A...I have a power supply that was 24V, 7.5A, and I installed a variable ac to it so I can adjuct voltage with a dial...when I tested output with my voltmeter, I get from 0 to 30.5V output...any ideas how I should set this power supply to work with this peltier, IF it will work for this peltier?

[Rich W]

Since your VMax is 24.6V and your supply is 24V, it would be best to run it at full voltage.. but since your supply won't push IMax (11.3 amps), you'll have to change the voltage down a bit so that the load of the pelt will match the output of the supply (obviously). Your best bet (since I do not know all the required info) would be to contact the manufacturer and ask them for the power requirement curves, etc.. explain to them your situation. Also take into account your cooling solution. If it is an air cooled peltier (or a not-so-adequate water cooled peltier), then you should consider running closer to the %75 input power (that is around hte input level that is most efficient [ie, most cooling power for least input power, and therefore least heat generated by the peltier]). So, you should get in contact with the manufacturer to find out how much current the TEC will draw as a function of voltage. If the manufacturer is TeDist.com, they will surely be able to help - they have a wonderful tech department. Also try http://www.peltier-info.com... haven't explored there much, just saw the link today.

Good luck!

PS - Be careful with changing the input power to your power supply with that transformer.. make sure it is within limits of design. For instance, it is is a linear supply and the output voltage exceeded the rating of the capacitors, then you could have experiend some troubles (bulging/breaking caps, etc) and could have damaged the supply.

You wrote:

RichW, please help me with some information...I bought a peltier that has specs: Qmax 172W, Vmax 24.6V, Imax 11.3A...I have a power supply that was 24V, 7.5A, and I installed a variable ac to it so I can adjuct voltage with a dial...when I tested output with my voltmeter, I get from 0 to 30.5V output...any ideas how I should set this power supply to work with this peltier, IF it will work for this peltier?

[Rich W]

That link should be: http://www.peltier-info.com
gotta watch out for the trasiling punctuations.

Oh, before I forget, another thing which I see alot is this:
People assume that the QMax of a TEC is the product of the VMax and IMax (related to my post above)... it is NOT.
Take the Drift-0.8 from tedist.com for isntance:
IMax: 11.3 A
VMax: 24.6 V
QMax: 172.0 W
deltaT: 69 C

Clearly, 11.3 * 24.6 != 172.0 (it equals 277.98 ~= 278). So, becareful when someone tries to sell you a peltier.. check up on all the specs, (do not assume that what they call the "wattage" of a pelt to be the QMax).

Rich W.

[Rich W]

Actually CablePro, if you are using a linear supply (thinking it is, sounds like one as to how it behaves...) then you can probably just hook it directly to the peltier in question and it'll work.. won't get 100% input power (probably more like 80%), but then you have that variable ac transformer (I'm assuming that is what it is). As long as you keep the input voltage within tolerance of the power supply, you'll probably be alright... just tweak it a little higher and use a volt meter to measure the output until it gets close to the peltier module's VMax (remember, don't exceed the input power rating of the power supply).

Good luck!!
Rich W.

[Cablepro]

I put it full dial for about 3 seconds with the multimeter already on the outputs...I figured it was bad to put it past 24V, so I dialed it down immediately...but thanks for the warning...so you think that if I put the power supply to 24V, even though it will probably only put out 7.5A, that I wont freak out the power supply considering the pelt has a 11.3A draw? or is that just maximum, and probably not actually the maximum for 24V?

in other words, is it probable that the 11.3A Imax is with lower voltage than 24?...

[Rich W]

If it is a linear power supply (big, heavy, big transforer(s), with one really big (or several good sized) capacitors), then the output voltage (if it goes beyond the specs of the capacitor(s), bridge rectifier(s), etc, could damage the supply... otherwise it'll probably be ok to tweak it up just a bit.

As per the problem you are having, go ahead and put the peltier up to it (if it's a linear supply). If it is a linear supply, then as you near the max output current for the given output voltage (ie, 24V at 7.5 amps), then the voltage will start falling... at some point an equilibrium will be reached (I don't want to work through the equations right now Also depends somewhat on the transformer/capacitor combination used, etc..) At this equilibrium, the voltage will be below 24 Volts and the supply will be outputing some current above 7.5 Amps... whatever point that coincides with on the peltier's input power curve. (Remember, you can't directly measure the resistance of a peltier with an ohmeter, because the current put into the TEC with the ohm meter will generate a temperature differential in the TEC and, by the Seabach (?) effect, it will create a voltage throwing off the resistance... I've heard you can use an LCR meter, but anyway...) But a lot of TECs (especially from tedist.com) will ship with the resistance on the spec sheet, so you'll have more of an idea what the voltage/current might be.

Bottom line is, if it's a linear power supply, just go ahead and hook it up (if it's a switching power supply, don't try it).
But, since you are 'working' the supply harder, the transformers + etc will get warm(er).. so make sure they get proper air flow for a longer life.. afterall, this is ProCooling.com!

Rich W.

[Cablepro]

another interesting note that I just recalled is that when I have the power supply dialed to 24V, the input voltage is only at 93VAC...

[Rich W]

Ok.. then it is a linear supply. Is it fairly heavy for it's size?

Also, try the supply at normal voltage (115) with no load. Is it near 29.7 volts (or even ~30)? If so, just go ahead and try to power the pelt with it.... just watch it to make sure it doesn't get too hot, and report the voltage that the supply outputs when the peltier is connected.


Rich W.

[Cablepro]

yeh...it's heavy as hell...transformer is huge, and the capacitor is bigger than a soda can...

yes, when I set it to 115V input, it's exactly 29.5V...damn, you're good...

I'll report what happens when I put the peltier load on it...right now I just have an 80mm case fan running on it at 24V night and day...I'm testing to see if the fan blows up...so far it runs great...great airflow...I know it's gonna kill the fan much quicker this way, but hell..they are cheap

[Cablepro]

Ok, when I hooked up the peltier at 30V, it blew my fuse...so I lowered it to 24V, and when I hook up the peltier(i'm only connecting it for a few seconds, because my watercooling is not setup yet), I also have my voltmeter connected at the same time...so wehn the peltier is hooked up at 24V, the meter reads about 16V...then I let the peltier cool a bit, and then I hooked up the meter inline to test amperage...when I have the peltier hooked up at 24V(which reads 16V on the meter when the peltier is connected), the amperage reads abut 6A for a second, then drops down to 5.5, then 5.0, then 4.5, then I pull the peltier off, because I don't want it running too long without cooling...please tell me what you think...this isn't really the result I was hoping for =(

[Rich W]

Ugh... sounds like the supply isn't big enough to drive it. What fuse did it pop? Seems like it's only pulling a few amps, so as long as everything else that is plugged into the same circuit (assuming it poped the circuit breaker....) isn't drawing too much (ie, no A/C, computer, big monitor(s), etc) things should be ok... hmm. Not quite sure what it means, but sounds like you'll need another supply I got a pair of giant rack mount linear supplies (48V @ 5 Amps each) for $2 each, plus shipping ($20 each for shipping). Might try something like that.... I would say that if you built the supply or if it was a VERY simple, custom-built one (like how I built mine in my article..) you could just change the transformer to a larger one that could handle more current. I'm not saying you couldn't do that now, but you'd have to be really careful about the health of the other components.. they might not be made to have more current pass through them, etc.. and watch out for the capacitors if you do (although I'd be tempted not to)... big caps like that can store a hell of a lot of charge... scary. Check ebay for some cheap 24v supplies. Sorry, dunno what else to say... other than try to keep the power supply and peltier on another, empty circuit and see how much input power you can give it without poping the breaker (or drawing too much current, etc).

Good luck!

Rich W.

[Cablepro]

I'm sorry, i probably wasn't clear...I installed a 1 1/5 (amp?ohm?) fuse...on the line in...that's the fuse that blew...

so the amperage dropping like that isn't normal? it's supposed to be steady?

I have black probe on negative output...goes into the meter...then I have the red probe attached to the black lead on the peltier...then I have the red lead of the peltier connected to the positive output...is this the correct way to measure the amperage?

When I'm checking voltage, i'm just connecting the black probe and the black lead to the negative output, and the redprobe and red lead to the positive output...

yeh...the amps start out at 7, then drop down, and never reach a steady reading...just keeps dropping, but then he pelt temp is too hot, so I take it off...I have no idea if it drops lower than 3.5

actually, after further testing, the voltage goes down to 16 momentarily, and then climbs back up to a steady 18.5V...I can't even test amps anymore because this meter just wont read amps anymore...I think I broke it...

just to mention: for the first 2 seconds, the cold side gets icey ice cold...then after about 4 seconds, the entire peltier is so hot I can't even touch it with my hands...Ihave to run with it, hanging by the leads and stick in the airflow of a fan to cool it off....might this indicate that it is getting decent power?

[This message has been edited by Cablepro (edited 01-25-2001).]

[Cablepro]

a little experiment:

I took some plastic wrap, and wrapped up 2 ice cubes with it, so that they would sit side by side flat...I held the ice cubes up against the peltier's hotside while I connected the leads to the power supply with my other hand (carefull not to get anything wet)...let me tell you something...the ice cooled the hot side well...it was melting the ice fairly quickly....

but, on the cold side, it got SOOO cold, it actually STUCK to my fingers...I had to peel it off of my fingers...I won't be duplicating this experiment, heh...voltage still stayed at 18.5V, but DAMNNN...it got colder than I expected...does this sound like the way it's supposed to behave?
__________________

[Rich W]

Yes, that sounds about right. And you were measruing correctly...

Now when you say that the output voltage stayed at 18.5V, that is less than the RMS values of the transformer(s) you have (I calculated that earlier to be 20V RMS, that's how I came up with that 29.7 V reading...) So, the voltage is below the RMS voltage of the transformer.. I don't know much about this case, but I know that it isn't too good.. both for the life of the transformer, and the 'quality' of the DC current... ie, there will be LOTS of ripple. Can you read to me the value of the capacitor? If you can, I think I can dig up an equation that will give the percent ripple of the power supply (ripple is how much the current varies... with a small load, the ripple will be less.. as the load increases, ripple will increase... a bigger capacitor can help). When ripple gets above anywhere from 5% to 15%, weird things can happen to the peltier.. either it won't cool as well as it could, or it might under go 'thermal stress'.... that occurrs when the power is cycled at a frequency less than 1kHz to 2kHz.. and that is bad for the peltier after a while. Can you measure the voltage output while attached to the peltier with the voltmeter in AC mode? Lemme know what that reads.

As for ther performance of the peltier, that is how it should behave when properly cooled.... becareful not to have the peltier exceed about 80 deg C though... at that temp (normal) peltier modules will be destroyed because that is the temperature at the solder which holds all the tiny modules inside will melt at. Some 'high temp' modules can whithstand up to 200 deg C, but by far most are 80 deg C modules.

Also, I'll make up a chart here in the next few days that might clarify some things... we'll see.

LMK...
Rich W.

[Cablepro]

with the meter in AC mode and attached to the outputs along with the peltier, it initially reads abot 35V, but then quickly climbs up to 40v, and stabilizes there...

as far as the capacitor is concerned, I don't see any numbers or anything anywhere...it's a big blue thing about the size of a soda can, and connected to the terminals is a little square block that says 5000W(i believe to aid in getting rid of the juice when it's turned off?)...

I really want to do this right...can you please suggest a capacitor and transformer to replace these with? Please give me whatever details I would need to actually search for them and make a purchase...

I feel like an ass for spending $100 in parts to put this thing together =(...my wife's gonna kill me, heh...

I need a way to make this situation work

hrmm...something i'm thinking about...could it actually be the variac(variable ac transformor) that is bottlenecking me? I was just looking in a catalog, and they are selling a 0-140VAC variac with 20A output for $165.00...mine was only $25.00, heh...I wonder if it's not allowing the amperage...is this possible?

Thanks bigtime

[This message has been edited by Cablepro (edited 01-25-2001).]

[Rich W]

Yeah... that might be it.
Can you try it without the variac then?

Also, you say you built this. Do you have a schematic anywhere of it? or a parts list or anything like that? Without that, it's really hard to know what to replace things with...

Rich W.

[Cablepro]

I mean I built it in the sense that it is an open frame power supply and I wired the variac to it...that's about it...it's PowerOne unit...must be old

what kind of specs should I be looking for to power this peltier, if I decide to replace this unit? to be honest, I'd really rather not run the peltier at it's full 172W, but more like 120-140W range...but I don't want to use my power supply if this is damaging the peltier