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How to connect LED light fixture and Peltier cooler in same DC power supply without reducing their capcity? Answered

I have a atx power supply which i have converted to 12 V DC power source,  current rated as 22 amps. 
I have connected a LED light appliance(90W) and a peltier cooler(62.2 W, Umax =15.4 v, Imax = 7 amp,1.7 Ohm resistance ) in parallel connection. But when i attached both of them to the PSU , my LED lights dim. What is the reason for this ?? 

I have tried with other combination that is peltier cooler and CPU cooler fan and find that the fan is not operating in same rpm when it runs as a sigle device with PSU. Is Peltier cooler make the circuit short??

Discussions

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mpilchfamily

Best Answer 3 years ago

So your expecting that the 2 devices will be pulling about 12A from the PSU. Check the wiring of the PSU. If you only using one of the yellow wires it may be limited in the current it can provide. Often PSUs will have more than 1 12V rail. Meaning they are on separate sets of circuits in the PSU and will have separate current limits. Often the 12V wires feeding the CPU are separate from those going to the rest of the motherboard and peripherals. If the PSU has the dedicated video card connectors they may also be on a separate rail. In many cases the sticker on the side doesn't reflect multiple 12V rails.

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Wired_Mistmpilchfamily

Answer 3 years ago

+1

Look for a Rail Labeled "12v-2"

Split the current between two Rails, And be sure you Have a good current draw on the 5V Rail. If you don't do this it can cause the Voltage Variance that you are describing.

Switching power supplies need draw on both 12v and 5V rails to work properly. You only need a good Amp or two (*On the 5V Rail*) Use say a Fan and some extra Led's? Remember, your asking it to do something it wasn't designed to do; Be nice to it :)

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AdnanN1Wired_Mist

Answer 3 years ago

Actually I took all 12v wires and ground wire to get only 12v DC output. So now i know that, I need to draw some current from 5v also to stabilize the voltage. Thanks for your suggestion Wired_Mist.
If i put dummy load on 5v , Like 5W resistor, is it ok??

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Downunder35mAdnanN1

Answer 3 years ago

I use 2 5W 12V globes on the 5V rail.
Gives you a nice indicator that all is working and they last forever.

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Wired_MistDownunder35m

Answer 3 years ago

My personal Fav too,

You ever notice if putting a 12v device on a 5v Rail effects stabillity?

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Downunder35mWired_Mist

Answer 3 years ago

Never had any issues with stability unless I overloaded.
Problem is that those power supplies provide the 12V "as a bonus".
The main power is on the 5V rail and it must be very good regulated.
But the power supply can not regulate without a load being present.
Sure it is a waste of power and noone needs a light but everything else means modifiying the internal electronics.

Tried it a few times to get different voltages and even once in an attempt to get rid of the 5V load problem - did not work so I reverted back to the lamps ;)

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Wired_MistDownunder35m

Answer 3 years ago

That actually explains a few things i was wondering about lol

Thanks for the tip !

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Downunder35mWired_Mist

Answer 3 years ago

You're welcome!
By the way: ost PC power supplies provide insame Amps on the 5V, even the old ones before we had multi core processors.
They make exellect supplies for bigger LED setups.
The only downside is that they need a load of around 10W to properly stablise the output, some even shut down if the load is not big enough.
Check Google for PSU mods ;)

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Wired_MistAdnanN1

Answer 3 years ago

I used resistors only once (5W also); Found they got way too hot !

If your hitting your local Electronics shop I'd kill a dollar and buy one anyway. But try to use Things like fans, Led's and pilot lights so the energy is used actually do something, Rather then just produce Heat :)

Lastly I wouldn't suggest combining them all together like you mentioned. If you do that then the max current is limited to the lowest Rail. (Check Pic)

If you PS only has a single 12v Rail (OR) the combined current is less then the Lowest Rail, then don't worry about it and carry on with your plan.

I would still suggest keeping the 2-3 12v Rails separate, and use one for each load.

PS: If you find my answer helpful why not click that Blue button ?

I won't get the cred, but Mpilch up there would be Grateful :P

EnermaxLiberty500W_Specs.jpg
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AdnanN1Wired_Mist

Answer 3 years ago

:).
I have only one 12v rail.. and as per your suggestion powered a small FAN and now the system is running good. Thanks Dude.

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Wired_MistAdnanN1

Answer 3 years ago

Awesome; Happy it worked out for you !

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iceng

3 years ago

22Amps is pulling your PSU voltage down.

You should do what Downunder recommends :-)

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Downunder35m

3 years ago

Check the voltage coming out of your PSU first.