Powering LEDs

Hi,

I have some 1W LEDs (forward voltage 3v). Want to know whether I can power them this way:

AC-DC adapter (output 9v) directly connected with 3 LEDs in series. Would the LEDs burn? Would the adapter become too hot and cause fire something like that?

Thanks.

hanyc93: Would the LEDs burn?

Maybe. It's certainly not safe.

LEDs always need at least a resistor, high power LEDs need current regulation.

hanyc93: AC-DC adapter (output 9v) directly connected with 3 LEDs in series. Would the adapter become too hot and cause fire something like that?

Depends on whether or not it's a regulated power supply. If it's for powering battery-powered toys then most likely it's not regulated and will output a lot less then 9V when you put a load on it.

The way to tell is to measure the voltage with no load. If you see much more than 9V then it's not regulated.

Depends on the power rating and load regulation capabilities of your Adapter.