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Question about low voltage power supplies Answered

I have several wall plug power supplies. The voltage on one says 12v 300ma but on my multimeter im getting 17 volts. Why is it 17v and not 12v?


what trialex said is true. this is also why, on the thread of how to convert under car neons to run on house power, i recommended against a wall wart power supply. to correct the problem and ensure an even, continuous 12 volts, you can do one of the following: install a zener diode accros the positive and ground leads to regulate power install a 7812 voltage regulator install a mosfet vcr

I was going to use the power supply to run a 30 LED array. The 7812 voltage regulator might be what I need to help.

30 leds in paralelle?? you may draw too many amps for a 7812. consider a zener diode

I think it was around 220-240ma for what im looking at running 33 leds. I was going to run 11 3 LEDs series with 15ohm resistors. LEDs 3.9fv 20ma

ohh. in that case, just use the 7812

Rob K

10 years ago

I pluged it into a 12DC fan and checked with the multimeter agin wile it was running around 13v.

Because it's a cheaper model and not regulated. The voltage of non-regulated power supplies typically sag under load - so to ensure they still deliver 12V under load, they produce a bit more when there is no load attached.