Regarding LED polarity. K means cathode right?

turntablemonkey

New member
I just built the moonshot tremolo and it didn't work at first. I had to reverse the LED that is enacting on the LDR and it works perfectly. Thing sounds gorgeous. But I'm so confused as to why it works when soldered in reverse to what the pcb says?
 
How did you determine the anode/cathode of the LED? Have you tested it outside of the circuit?

A few people have reported LEDs working reversed in a few different projects.... I'm curious if there are some floating around with the wrong lead clipped short or the flat edge on the wrong side of the plastic lens.
 
Didn't test outside of the circuit. Based entirely on the flat side being the negative. I had an issue with a led only working on the parentheses when in reverse aswell. Leds were ordered from tayda. Is it possible to check for polarity whilst installed in the circuit with a DMM? Would be great to know if my components are reversed for future reference.
 
You can sometimes light an LED in-circuit using the Diode Test mode of a DMM, the resistance mode may work as well depending on the meter.

With no power applied to the circuit put the DMM leads directly on the leads of the LED, when the LED lights the red probe is on the anode.
 
How did you determine the anode/cathode of the LED? Have you tested it outside of the circuit?

A few people have reported LEDs working reversed in a few different projects.... I'm curious if there are some floating around with the wrong lead clipped short or the flat edge on the wrong side of the plastic lens.

I use these from tayda and they have always had the flat edge reversed from convention.
 
Ok, yeah. Tested it and turns out the leds from tayda are reversed. Good to know. I didn't realize that was a possibility. Time to see if that's why my parentheses isn't working.
 
I keep a 2032 battery on the bench just to be sure the light comes on and it's the color I'm after. (y)

Edit...oh yeah....and to check polarity too!
 
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