i realized my peltier is 4A after i bought it , its already in way ! the 12v+ adapter i ordered is 1A , is there anyway i can power the peltier ? i don't care if it doesn't cold as full power ! im going to make a mini fridge, + make it turn on and off automatically based on temp !
also if it is 4A i don't think it can be cooled with a simple old Sapphire 7750 heatsink (i guess i need to water cool it or something , or use a decent copper heatsink like evo 212+ !)
like i can power a 12v motor with 5v+ but not powerful as 12v+ ! or turn led with lower Amperage and it still gets on but dim !
That would depend on whether the 12V supply is overload/short-circuit proof or not. If it is, it will just lower the output voltage enough to keep itself within safe operating parameters. If it is not it will probably get damaged. Either way none is a optimal solution.
Also remember, a peltier element has a relatively bad efficiency which means it generates heat in order to cool. This means that the hot side of the element needs a heatsink that is dimensioned to handle both the cooling power and the loss power
i already prepared a dead gpu heatsink for it !
says 12v wall travel charger 1A
nthing about protection !
nothing i can do with resistors or ect ?!
its only 1$, so its unlikely it will have anything !
guess i just have to use my old PSU
Yes, you can limit the current by connecting a resistor in series. But that will generate more heat (that is what resistors do) thus lowering the efficiency even further
:o how can i do this ?(calculating ect)
by efficiency you mean the voltage and power that is wasted ?
- i have a voltage lower, i guess its a switching regulator !
this is what i have :
You'll even less efficiency running a peltier at 25% nominal, they are already
very inefficient... Peltiers are good conductors of heat so if you don't drive them at
high levels you lose significant heat through conduction (that's the main reason
they are inefficient in the first place I think).
But then again we don't know how much heat you want to pump with it.
But no, that supply will not like the load, if its well engineered it will shutdown
or drop voltage safely, if not it could overheat.
If we assume that the peltier element acts as a linear resistor we get R=U/I (ohms law) That gets us R= 12/4= 3 ohm.
What we need in order to keep the current at 1A is R=12/1=12 ohm. So you have to connect a resistor of 12-3=9 ohms in series. The power dissipated in this resistor is IIR 119 = 9 W. So you will have to get a 9ohm 10W resitor.
Now for effiency. Your circuit will consume 12V*1A=12 W. Of these 12W 9 will be wasted in the series resistor, leaving 3W for the peltier element. Since these are offering about 10% efficiency the cooling power will be 0,3W (of course depending on temperature difference)
So the total efficiency of your system would be 0,3/12=0,025=2,5%
that 4a one was the lowest Amper i found in my country
sounds like my best option is the old psu, as you say at low amper and voltage it will be bad !
anyway, is there any other way to cool a minifridge other than peltier, because it wastes a lot of energy as i see,
One way to get some 12V power is using a salvaged power supply from a pc.
I built a mini fridge myself. The cooling power is dependent on the enclosing surface and the k-value of the insulation. I used 50mm styrofoam wich worked quite well but since i wanted a see through door i encountered some problems. I ended up with 3 sheets of polycarbonate with 10mm distance between them. That worked together with a rather small peltier and a large cpu cooler on the outside. The inside was about 14C perfect for wine.
Of course you could just do it right and buy a power supply. This one is 5A and $18. They stock them all the way to 10A.
i use my old pc psu
but that sound complicated and hard, ! im not sure i can get that material and stuff here ! maybe i should just give up or make a non isolated one ! or just one that you can place your drink on, (not a fridge, just too keep a coke cool )
here is my heatsink, im worried its not enough !
will post here about how it went
(btw, do i need a heatsink on the cold side to make the fridge room get cold easily?! if i just end up with a little plate that you can place your drink on it ! im also willing to add a warmer mode ! (2 7ohm transistor in series:D)