HeaterMeter4.0 Panel Mount LED


Dale Ward

Does any one have LED picked out for panel mount?
What would the voltage and amperage limits be for them?
I found lots of choices but don't want to screw up my board.

Bryan Mayland

TVWBB Hall of Fame
The resistors on the LEDs are a bit over-specced. The source voltage is only 3.3V and the resistors are 390ohm so for the Red (1.85V forward) that is 4mA, Yellow (2V forward) is 3.5mA, Green (2.2V forward) 3mA. For typical light output that means Red 90mcd, Yellow 192mcd, Green 6mcd. The resistors really should have been 150, 150, 120ohm for roughly 10mA each but I did the math at 5V and forgot to redo it once I went to 3.3V VCC.

That's a lot of information but the numbers you need are 3.3V source voltage, 390ohm resistance and then feed the forward voltage for any LED you're considering into a LED calculator to find out how many mA you're going to get and make sure it is under the rated current for the LED. Really, you can't go wrong with any 3mm LED that's not white or blue.