Hi Andrew, =20 Sorry for not being clear. I am working on a project using a PIC (16F877 = or 16F628 ) or even AVR (90S2313, 90S8515) to control 4 relays (2 pairs);= on and off for say, 8 seconds interval for 24/7. Powerheads (fish tank t= ype) operating at 220v will be attached to the relays. During the day, wh= en the fish tank lights are on, I want the on/ off interval to be 8 secon= ds. During the night when the lights are off, I want the on/ off interval= to be 4 seconds. Thus, I think of using a light sensor as an input logic= so as to use different interval routines within the PIC. =20 As I am totally new to MCU and electronics hence, if I can get hold of a = project that is as close to my requirement as possible, that will greatly= help. The only plus I have is, I have some BASIC programming background.= Hopefully, I can pick up quickly on modifying the source code to suit my= needs. =20 Thanks in advance for the help. =20 cheers, Andrew Rich wrote: Here is the flow 1. Get the datasheet 2. Download MPLAB 7.0 3. Use MPLAB to simulate, syntax check and create the HEX file used for programming 4. I use a PIC programmer that hangs of the serial port 5. Surf the web for little examples i started out turning lights on and o= ff What specifically do you need to know ? Ask lost of questions --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist =09 --------------------------------- Do you Yahoo!? All your favorites on one personal page =96 Try My Yahoo! --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist