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Topic Title: Help with simple electronic issue
Topic Summary: disabled alarm system commoning up signals
Created On: 13 July 2013 10:18 PM
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 13 July 2013 10:18 PM
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Posts: 166
Joined: 23 December 2006

Hi all, have s simple electronic problem that i could do with help for a solution to.

Basically we have a disabled refuge system which is a C-Tec sigtel sytem. It is also linked to the disabled toilet alarms. The alarms used do not have a built in relay as shown in the instructions so we have used the stand alone relays to go with each system. The problem we have is that we have a situation where we have two disabled toilets next to each other and they both have a sepperate system installed in each toilet. We have the issue that we have no spare channels in the system to indicate each individual toilet on the panel. As they are both next to each other we proposed to join the two outputs together and indicate this in the panel text.

The electronic problem i am struggling with is the system has a EOL and a trigger resistor installed. I may be being blonde here , but i cant think how to connect them together so that whichever one is activated will trigger the sytem and not create a short circuit.

The below is the link to the instructions. P18 has a diagram of what i am struggling with

I would be grateful if any of you could have a look for me and come up with a solution to this simple problem.

Thanks in advance

 15 July 2013 11:33 AM
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Posts: 1918
Joined: 28 May 2002

Disclaimer: This is based on a VERY quick look in a coffee break, so no guarantees!

I'm assuming that what you want to do is connect two switches to one controlIer, with each switch as shown in section 11.5. If I'm reading this right, all that happens when the call happens is:
- C connects to N/O,
- which switches the trigger resistor in parallel with the EOL resistor,
- so the resistance between Line in + and Line in - drops from 1.5K to 750ohm.

If this is the case the connection to N/C is not needed - other than being a convenient place to terminate the wires and resistors. By removing the connection to N/C it looks like you can wire two units in parallel (C to C and N/O to N/O). Then either (or both) will trigger an alarm.

- Line in + connects to EOL resistor and trigger resistor;
- Other end of EOL resistor connects to N/O of both boxes and Line in -;
- Other end of Trigger resistor connects to C of both boxes.

The worse that will happen is that if both alarm at once the resistance between Line in + and Line in - will drop to 500ohm (1.5k / 3).

Hope this helps...

Andy Millar CEng MIET CMgr MCMI

"The aim of argument, or of discussion, should not be victory, but progress." Joseph Joubert
 05 August 2013 12:15 AM
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Posts: 433
Joined: 15 April 2013

surely the easiest way is to connect them together via a pair of diodes?

Ken Green

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