Variable pwr supply

[zachtheterrible]

I've got a variable pwr supply, nothing fancy, it's just a transformer w/ a switch on it that gives you 1.5, 3, 5, etc. On 12 volts, I am registering 18 volts on my multimeter!! Waddup w/ that?

 

[bmcculla]

If its just a transformer then the outputs are going to be AC. AC voltages are usualy measured in volts RMS. RMS is nice because it lets you treat it as DC for calculating Power. But the Peak to Peak voltage is higher. just multiply by square root of 2 to get the amplitude in volts.

Just out of curiosity where in California are you. Im in the San Francisco bay area.

Brent

 

[zachtheterrible]

DANGET, I forgot about RMS Grrrrr :evil: . Anyways, the output is DC, so does RMS still apply?

I live in Temecula, it's about an hour north of S. Diego, just incase u didn't know (but i'm sure u did)

 

[Johnson777717]

If I may add another point. If the power supply is not regulated, the load volts will be lower than the unloaded volts. For instance, you measured 18 volts from what was supposed to be a 12 volt output, correct? Most transformers will ouput a higher voltage when they don't have a load on them. Put a load on the transformer, and the voltage should drop to a reasonable level.

NOW, place a load on the output of your power supply (A computer fan, or high wattage resistor will do) then measure again. If the voltage drops, then your power supply is not regulated and you're experiencing the poor regulation of the transformer. This really doesn't necessarily mean that you have a bad power supply. It just means that the supply isn't regulated very well.

 

[zachtheterrible]

That make much sense, thanx!!