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Resistor Values

A project log for Binary Pomodoro Timer

Binary LED countdown timer for productivity.

robbie-nicholsrobbie nichols 05/28/2015 at 02:320 Comments

I'm sure most people reading this already know about how to use resistors with LEDs. I bought a cheap bag of assorted resistors without data sheets to know their voltage drop, so I searched the internet with duckduckgo to find a handy site that has some good guesses for the normal values there so I can get on with specing me resistors. I put it in a quick spreadsheet, and here are the values I got initially:


drop resistor value
Green 2.1 223.0769230769
Yellow 2 230.7692307692
Red 1.7 253.8461538462
Blue 3.4 123.0769230769



supply voltage 5
target current 0.013

I will rummage through my resistors to get close to those and see if I'm happy with the brightness. My target current seems low enough that I can make some pretty bad mistakes here and not worry about it.


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