On Wed, 14 Jul 1999 11:34:38 -0400 Wagner Lipnharski writes: >Minimized yes, wiped out not. >This "cleanning up" effect is increased in "saturated core" >transformers, but not 100% efficient. >Much better results using electronic components to wipe out those >nasty >glitches, things you can buy at Digikey for less than $1. Take a look >at their catalog about TVS's, Transient Voltage Suppressor. > It seems, however, that between transformer core saturation, the current limit resistor, and the clamp diodes on the PIC that the device is adequately protected. I have a few thousand theatrical dimmers out there where zero cross is detected with diodes from each end of the transformer secondary, a couple diodes, a "pull-down resistor", then a current limit resistor into the INT (RB0) input of a 16c74. Measurements on the transformer indicate the core saturates pretty quickly as normal line voltage is exceeded. The current limit on the PIC clamp diode and the value of the current limit resistor indicate the transient would have to be substantially above what comes out of the transformer at saturation. There have been no failures of the circuit. If there had been, I'd be tempted to add a zener or TVS after the diodes. Harold Harold Hallikainen harold@hallikainen.com Hallikainen & Friends, Inc. See the FCC Rules at http://hallikainen.com/FccRules and comments filed in LPFM proceeding at http://hallikainen.com/lpfm ___________________________________________________________________ Get the Internet just the way you want it. Free software, free e-mail, and free Internet access for a month! Try Juno Web: http://dl.www.juno.com/dynoget/tagj.