Stir plate power supply question

So I am building a stir plate, and the power supply I originally used wa 5 volts and .3 amps. Needless to say it doesn't have enough juice to power the fan once I hooked in the potentiometer. I got a hold of a 5 volt 2.5 amp power supply. Will this one work? I want to make sure before I go into soldering all this stuff apart and back together again. I imagine it should have plenty of juice now.

Your problem might not be the current but the voltage. Is that a computer case fan your using? then I would strongly suggest looking for a 12v supply as that's the voltage their used to receiving from the computer PSU.

I read on here that people were using 5v power supplies but didn't mention the current rating. I'll give this one a shot I guess and see what happens. It was free so whatever.

I originally had a 12v power supply hooked up to mine with a potentiometer and it just kept throwing the stir bar, then I found a 9v power supply and it worked perfectly. I would take out the potentiometer if you use the 5v and see if that works.

bchurch said:

I originally had a 12v power supply hooked up to mine with a potentiometer and it just kept throwing the stir bar, then I found a 9v power supply and it worked perfectly. I would take out the potentiometer if you use the 5v and see if that works.

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great suggestion! If it works great at that one speed then done and done. If not , then I would also possibly suggest a weaker pot, you could be throttling it way to much

bchurch said:

I originally had a 12v power supply hooked up to mine with a potentiometer and it just kept throwing the stir bar, then I found a 9v power supply and it worked perfectly. I would take out the potentiometer if you use the 5v and see if that works.

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I've got a 9V in mine and it works great.

Ok, I'm using the pot from the easy stir plate build thread. I'll try this power supply first. The fan works without the pot on the 300mah phone charger, so I am hoping the boost in current flow will help.

Ok so the five volt one doesn't work. On the hunt for a 9 or 12 volt one now.

Potentiometers, hooked up with only two wires (as they are for stir plates and most other simple DIY projects) are just a variable resistor, aka rheostat. Resistors work by converting current to heat, and dropping the voltage. The power supply will raise its current output, up to its maximum, to meet the load demand. Voltage downstream of the resistor, however, will be less. Most computer fans need about 5v to spin to begin with. A 12v power supply would be best, since you have a pot to adjust voltage anyway.

Also of note, if the power supply is unregulated (which it probably is - cell phone chargers rely on the battery's protection circuitry to run at 5v), you were probably getting more than 5v out of it when it was just hooked up to a fan, maybe 7-8v. Once you added the resistance of the pot in, it dropped voltage back down to it's design output.