At 07:53 AM 4/16/2008, you 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 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)

How about a couple of cross-coupled BJTs with load and base resistors?
(an RTL, and I don't mean register-transfer-logic, S-R FF).

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com



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