At 09:21 PM 8/8/2015, IVP wrote: >Hi all, > >I've got 12VDC geared motors here which a client wants to use in >his product > >(3) PWM the motor from 0 to run current We used to build a product that used a large linear actuator running=20 at 12 Vdc. We spent a LOT of time on that project, trying to make it=20 reliable in the long term. Our final version used 2- decent-sized=20 relays (AZ2150A) and 2- sense-FETs from IR. The relays did the=20 high-side switching in the H-bridge, the sense-FETs did the low-side=20 switching and PWM. We used a 5c032 CPLD to control everything (long=20 before we started using PICs). Everything was sequenced: relay would=20 close first, delay, PWM up to full speed, then ramp down, PWM off,=20 delay, relay off, delay, both sense-FETS hard ON for braking. Some of those units are still in use today. Relays are holding up=20 very well, as are the FETs. The customers have had to replace the=20 linear actuators - the brushes fail after a few years of constant=20 back-and-forth movement. My suggestion is to either replace the relay with a decent MOSFET=20 (and catch diode) *or*, if you really want to have the relay in the=20 system, add a series MOSFET that you can do PWM with. Again,=20 sequence things so that the relay contacts are never changing state=20 while current is flowing. dwayne --=20 Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .