I am looking to build a few led arrays utilizing the typical wall wart DC power supplies....I have a pretty good assortment of them in all kind sof output DC volts.....Figureing the resistor is not a problem, but what my problem is is with the actual wall wart itself.
For example I have one that says input 115 VAC output 12 VDC but its out put as neasured with a voltmeter is 17VDC
ANother is rated at 7.5 VDC on its data plate, but it measures 9 VDC output.....
Even brand new ones are somewhat higher than their stated output voltages, so what figure do I Use....My actual measured voltage or the data plate info on the power supply? I finally got thre led stuff figured out, now these power supplies throw me a curve......
Would it be that soome were used in various devices to recharge a battery, and the output is somewhat higher than its rated output, due to it needing to be a bit higher to recharge a battery or?
Any info greatly appreciated..