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'[EE] SR latch for 24VDC'
2008\04\16@075135 by Dennis Crawley

picon face
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)









2008\04\16@081246 by Spehro Pefhany

picon face
At 07:53 AM 4/16/2008, you wrote:
{Quote hidden}

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"
spam_OUTspeffTakeThisOuTspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com



2008\04\16@081503 by WK

picon face
Dennis:

Take a look at the 12HV615.

Kind Regards
Bill



-----Original Message-----
From: .....piclist-bouncesKILLspamspam@spam@mit.edu [piclist-bouncesspamKILLspammit.edu] On Behalf Of
Dennis Crawley
Sent: Wednesday, April 16, 2008 6:54 AM
To: Microcontroller discussion list - Public.
Subject: [EE] SR latch for 24VDC

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)









2008\04\16@081633 by Vasile Surducan

face picon face
On 4/16/08, Dennis Crawley <.....dennis.crawleyKILLspamspam.....usa.net> 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):
graffiti.virgin.net/ljmayes.mal/var/optoltch.htm
However depends what kind of signals are available at your inductive
sensor output.


{Quote hidden}

> -

2008\04\16@082907 by Dennis Crawley

picon face
OK :)
I'll try that.

On Wednesday, April 16, 2008 9:14 AM [GMT-3=CET],
Spehro Pefhany  wrote:

{Quote hidden}

2008\04\16@083915 by Dennis Crawley

picon face
Very simple and interesting,
Thank you Vasile.

On Wednesday, April 16, 2008 9:16 AM [GMT-3=CET],
Vasile Surducan  wrote:

{Quote hidden}

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