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Fwd voltage question

Started by fasteddie455, June 08, 2017, 04:00:54 AM

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fasteddie455

Howdy, I am attempting to build the Twin Peaks Tremolo by David Rolo and in the notes he states "LED1 is there to increase the output of the voltage regulator (5V + the Forward voltage of the LED). Try to find a LED with no more than 2V FWD voltage to make sure the voltage regulator still has enough drop out voltage to operate correctly."
now I am having a devil of a time finding a LED of any color whose max Fwd voltage is 2 or less. Am I misunderstanding something? what should I do? Any help would be greatly appreciated1 Thanks!
fasteddie455  

somnif

Diffuse reds tend to be in the 1.8-2v range. Or at least those I picked up from Tayda are.

fasteddie455

Is this something I have to measure on each actual LED or is this something that you just read the range in the info provided by the seller ? The 5mm red super bright one that I see on Tayda's site lists a range of 1.9 to 2.1 V.  The water clear ones are even more. Thanks for the help and for putting up with my ignorance.

fasteddie

somnif

The data sheet will give you the general range, but you can measure them directly easily enough with a DMM (though some cheap DMMs have trouble with diodes above a certain vf, mine will tell me up to about 1.9v). Most layouts of this circuit I see use a 3mm diffuse red LED. 

fasteddie455

Cool. I measured one of mine today and it was 1.78.so I reckon I'm in business! Thanks for the help!
Fasteddie455