Re: 12v DC power supply read 18v


"Bob Eld" <nsmontassoc@xxxxxxxxx> wrote in message
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"Ed" <jag_manR__EM*-0_V_E653@xxxxxxxxxxx> wrote in message
news:K1lRj.25$3O7.19@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I bought a cheap 12v DC "wall wart" to operate a simple LED garage
door open alert. The circuit
has only a microswitch, a 1K ohm resistor, and 12v flashing LED.
However, the power supply
open-circuit voltage is actually almost 18v. Is this going to fry
the
LED? Should I perhaps get
a 9v DC unit and hope it reads closer to 12v?

TIA

Ed

No. This transformer will not hurt the LED.

The max current will be about 16mA which is way below the max rating
of the
LED. Most LED's can take 50mA or more. Furthermore, any additional
load on
the transformer will drop the voltage toward 12 Volts resulting in
an even
lower LED current. The 12 Volt number is a loaded rating.



Thanks, Bob!

Ed


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