At 06:46 PM 9/14/02 +0100, Alan B. Pearce wrote: >OK, here are the "power dissipating blocks" as I see the circuit. > >1. Some LED indicators (about 4, of which probably only 2 on at any one >time). > >2. Often present. 2 x 10 led bargraph (one run by LM3914, one digital >drive), 1 x 4 digit 7 >segment display with digits multiplexed. As I see it, the power-hungry devices are the LEDs. All the other stuff should consume less than 30 mA or so - that includes all 3 PICs, the op-amps, a LCD display. Heck - even a 78L05 would probably work just fine if it weren't for the LEDs. 1) the LM3914 can operate from the un-regulated supply. It will get hot if operating in bar mode but will work quite nicely in dot mode. 2) How many of the other LEDs can be made to operate from the un-regulated supply? 2003 or 2803 type o/c buffer chips are cheap - compare their cost to the cost of the switch mode supply. There are a few LEDs that might need to be driven directly by PIC pins - such as in item (1) in Alan's message. Run them at 4 or 5 mA and add that current to the 5V supply. They don't need to be blinding - just visible. The cheap T1 LEDs I am currently using are nice and bright at 4 mA. dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 18 years of Engineering Innovation (1984 - 2002) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads