----- Original Message ----- From: "Daniele Salatti" To: Sent: Saturday, August 09, 2008 2:06 PM Subject: Re: [PIC] Help on PIC16F628A - blinking LED > Hi! > > >>> Is it a solid on ? Might there be a fast on/off loop ? How does its > >>> brightness compare with a steady 5V supply ? > >> > >> Compared with a steady 5V supply the brightness is lower... This could > >> be a symptom of a too fast on/off loop? > >> > Can someone suggest me a place (link) where to find a working code to > make a LED blink with a PIC16F628A? Maybe it would be usefull to compare > it with my code... Hi, I can't help you with the code but if you want high (apparent) brightness and high efficiency from your LED then drive it via a transistor (bi-polar or MOSFET) at about 5 times the rated current on a 10% duty cycle. Athough you only need about a 40 Hz repetition rate to avoid visible flicker you should use a minimum 1 KHz repetition rate to be safe. I would be inclined to use a 10 to 100 KHz cycle. You can breadboard a test using a good old 555 to find your operating parameters. Your LED datasheet will tell you what duty cycles and currents are acceptable, although if you understand what you're doing you can safety exceed the specs. I've driven LEDs directly from 5V using a 1 MHz repetition rate and a < 1% duty cycle. Although the peak power was approaching 10 W the average power disipation was <100mW. Best of Luck, Bruce -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist