At 09:33 AM 3/23/03 -0500, Sid Weaver wrote: >I am try to drive a 1.36" LCD with a shift register. Each register output >goes to ground via a trimpot. The wiper of each trimpot goes to the >corresponding segment on the LCD, and is adjusted for approx 2.9 VDC. Common >on the LCD digit is pulsed by a 100 Hz 50% duty cycle square wave >(adjustable). Wrong approach. Try this: connect all 7 segments AND the backplane to the 8 bits on the shift register. Arrange your code so that the shift register refreshes somewhere between 30 to 100 times per second. Send normal data to the segments and set the backplane LO. About 30 ms later, invert the data (including the backplane) and send the data again. Repeat at about 30 Hz rate. You wind up with a 30 Hz AC signal on the backplane and segment data lines. If a segment has to be ON, it is inverted with respect to the backplane. If a segment is OFF, it is in phase with the backplane. I have code that does this for a 4 digit LCD display - it was not difficult. Display is directly driven from 4- 74hc595 shift registers. dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 19 years of Engineering Innovation (1984 - 2003) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' 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