Opto coupler.

F

Thread Starter

Fredrik

I'm shifting control system in a old system.
There are some old alarmpanels with outputs on them. These outputs are Opto couplers..
The problem is that the input on the PLC goes hi when there is no alarm ie it's inverted.
This should not be the case and it must be a result of different voltages.

The panels power supply is 24VAC
The PLC:s 24VDC (Different transformers)

The inputs of the PLC are driven by -6VDC.
The PLC is a SAIA PCD2

If someone has any idea about how i could get this to work please help me.

Fredrik
 
J

Johan Bengtsson

Is that really a problem? I would have liked that since it probably is more fault tolerant (ie higher probablitity to loose a signal when you should have one instead of getting one when you shouldn't. Not much difference but the small difference there is should work in that direction)

Isn't is easier to just invert it in the PLC instead of trying to change the hardware...

Johan Bengtsson
P&L, the Academy of Automation
Box 252, S-281 23 H{ssleholm SWEDEN
Internet: http://www.pol.se/
 
J

Johan Bengtsson

Ok, I know this looks silly, a reply to my own reply...

If you really want to change it, send some kind of drawing showing how it is connected now.

/Johan Bengtsson

-----Original Message-----
From: johan.bengtss[email protected]

Is that really a problem? I would have liked that since it probably is more fault tolerant (ie higher probablitity to loose a signal when you should have one instead of getting one when you shouldn't. Not much difference but the small difference there is should work in that direction)

Isn't is easier to just invert it in the PLC instead of trying to change the hardware...

/Johan Bengtsson

----------------------------------------
P&L, the Academy of Automation
Box 252, S-281 23 H{ssleholm SWEDEN
Tel: +46 451 49 460, Fax: +46 451 89 833
E-mail: [email protected]
Internet: http://www.pol.se/
 
We have inverted them in the plc to get it working and we´ll se if the customer can live with it.
The problem is that we also has diodes on the PLC and we can´t invert those. It can always be solved some other way if we has to solve it.
But what botherd me was that i there shouldn´t be a inverted funktion on theese outputs. And i know to little about opto couplers to know when they lead and when they don´t. Thought it was a good time to learn something. But don´t worry. The worst case scenario is that we will have to change the panels and get paid for it.

Fredrik
 
we had a similair problem with a comunication toshiba plc 110v siai pcd2 we solve it with relays 2 control the voltage
 
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