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I have an unregulated multi-voltage (knob-selector) power supply that I would like to power one of my external Arduino projects.

The power supply is a 230Vac Input, 3,4.5,6,7.5,9,12Vdc 1A from http://www.maplin.co.uk/ac-dc-multi-voltage-1000ma-power-supply-46107

When I measure the output (no load), no matter what voltage is selected via the knob my multimeter reads 17Vdc.

Would this be correct. I want to use 12Vdc to power my Arduino and also 2 small 12vdc motors (200ma) each. Will this be OK as the suppiler said that as soon as I apply a load to the power supply it will drop to the selected voltage. I don't want to pus this in to my Arduino just yet in case I burn it out with 17Vdc if the volatge does not drop to the selected 12v/

Thanks

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That should be fine. The manufacturer is right, unregulated power supplies have a voltage that depends on current. A "12VDC 1A" supply will supply about 12V (not exactly) at 1A, higher voltages at lower currents.

It's safe to power your Arduino this way, but do not power your motors through the Arduino's VIN pin. Just power them directly from the 12V supply. Otherwise the regulator on the Arduino will overheat with that much current and "high" voltage coming in.

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Thank you  smiley-kiss
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