This is my second post and I am not sure if this is right place to ask this.
But since I am planning to run this device on RPi I am posting it here.
I have an LED with "forward voltage " max 3V and forward current approximately 30mA .
I am test using wallwart transformers of various output specification and finding out that at no load the output
voltage is nowhere near the printed label spec.
For example - measuring transformer with 3.65V nominal idle output spec gives 8.5V output !
Connecting such transformer directly to LED reads 390mA ! ( The max current spec is 350mA) .
I have not read the voltage at the LED, but it does not light.
I just do not want to just connect any value resistors to have glowing LED.
Is there a way to guess / estimate the idle to some load output characteristic of an average wallwart transformer?
PS Yes I know Ohm's law.
But since I am planning to run this device on RPi I am posting it here.
I have an LED with "forward voltage " max 3V and forward current approximately 30mA .
I am test using wallwart transformers of various output specification and finding out that at no load the output
voltage is nowhere near the printed label spec.
For example - measuring transformer with 3.65V nominal idle output spec gives 8.5V output !
Connecting such transformer directly to LED reads 390mA ! ( The max current spec is 350mA) .
I have not read the voltage at the LED, but it does not light.
I just do not want to just connect any value resistors to have glowing LED.
Is there a way to guess / estimate the idle to some load output characteristic of an average wallwart transformer?
PS Yes I know Ohm's law.
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