On Friday, 13 April 2018 18:48:02 UTC+1, Tim R wrote:
On Friday, April 13, 2018 at 1:06:30 PM UTC-4, Ralph Mowery wrote:
LEDs do not really have a voltage rating as such. They are current
devices. You just have to limit the current to a safe level.

Okay. 12 volt car battery, 1k resistor, the most current you can get is 12 mA, any LED should handle that. But that's not the fault condition I was wondering idly about.



The LED will have a voltage across it of about 1 to 3 volts depending on
the type in the forward direction. That voltage is almost the same no
matter what the current is within reason.

My first thought is if he used one LED and connected it backwards, he could think a circuit was dead that was really hot, and burn up his new red sports car. Or he'd always have to fuss with getting the right lead on. I didn't realize he had a ground clamp and probe, so I was probably just wrong on this one. I was thinking two probes.

My second thought was if he uses 2 LEDs in parallel, and they're both above 5 volts, then they're both conducting. How much current goes through the forward biased one? enough to give a bright light, or maybe dim enough he thinks the circuit is dead and he burns up his new red sports car.

someone is not familiar with LEDs