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 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)









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