-2
votes
3answers
661 views

How do I calculate the required value for a pull-down resistor in a PWM circuit?

I'm using 74HC595 with SoftPWM to control some LED's. When the 74HC595 is off, its outputting about 0.57v, enough to turn my LED's on somewhat. How do I work out the value of the pull-down resistor ...
5
votes
2answers
483 views

Small, cheap, and simple driver for 16 RGB LEDs

I am working on a board design that will put 16 RGB LEDs in a circle around a rotary encoder. I want this setup to be simple so that I can run it from any micro with limited software (ie. built in PWM ...
2
votes
1answer
1k views

Functional difference between various astable 555 circuits

Looking through some 555 square-wave-generator circuits (possibly with variable duty cycle for 4-wire PWM fan control) I've found three different circuits: From the Wikipedia 555 article, a ...
13
votes
7answers
3k views

LEDs on a (battery) budget! – How can I lower the current through a LED without using up the battery?

EDIT: Here is a much brief version, the meandering motivated version is probably subsumed in the parent question on general battery life optimizations. How can I lower the current into a LED ...