Wall Wart Outputs

Thread Starter

djsfantasi

Joined Apr 11, 2010
5,829
I have a wall wart, whose output is rated 9VDC @ 500mA.
I am measuring 13.7 VDC unloaded. I put a 10k resistor across the output, expecting to see the voltage stabilize. It did - to 13.7 VDC. What am I doing wrong?
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Lestraveled

Joined May 19, 2014
1,946
You are not doing anything wrong. You take a 500 ma wall wart and load it at 1.4 ma. (.3% of rated current) and get very little change in voltage. That is what should happen. Try 50% of rated and see what happens.
 

MaxHeadRoom

Joined Jul 18, 2013
19,393
That must be one of the older linear W.W.'s which rely on the rated current to bring the voltage down, the vast majority now are SMPS and output a constant voltage level.
Max.
 
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Thread Starter

djsfantasi

Joined Apr 11, 2010
5,829
Thanks guys. Good to know, especially since the planned load is around 100mA. I guess I need a different wall wart.
 
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