Very simple and interesting, Thank you Vasile. On Wednesday, April 16, 2008 9:16 AM [GMT-3=CET], Vasile Surducan wrote: > On 4/16/08, Dennis Crawley wrote: >> Hi fellows, >> >> I'm trying to desing a very simple SR circuit to control >> two 24VDC signals coming from two CAMs inductive >> sensors) and one 24VDC output which is connected to a >> PLC input. (noisy machine) >> >> In most of the desings I've ended up with this (block) >> configuration opto--\ >> logic--opto >> opto--/ | >> | >> source (taken from PLC) > > > For me, looking to your description very fast, the > optocoupling section hasn't too much sense. > Assuming you are already use two optocouplers why do you > need another 555 for an RS latch ? I gues SR for you is > meaning SET-RESET latch, right ? > You can do it directly with optocouplers supplied from > 24V. > Look to this ideea (which is not a genial one): > http://graffiti.virgin.net/ljmayes.mal/var/optoltch.htm > However depends what kind of signals are available at > your inductive sensor output. > > >> >> For the logic part I used a 555 with reset and trigger >> tied to positive through 100K resistor. >> Since the 555 used 18V max,... I have calculated a 18v1w >> zener with a 100ohm1/2W resistor limitation to power the >> kit. >> >> I've also thought about a 12F, but I don't want a DC-DC >> converter,... unless it would be the best and safer way >> to do this task. >> >> True table >> S R Out >> REdge x 1 >> x Redge 0 >> >> Is there any chip out there that works over 24VDC >> directly? >> Should I have to desing this with Op amp? >> The challenge is to desing the SR on the 24VDC rail, >> with the less number of componentes as possible. >> >> I'll appreciate any hint . >> >> Cheers regards. >> Dennis (lurker) >> >> >> >> >> >> >> >> >> >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist