Retractive switches

[mike_d]

How does a retractive switch work to control absence detection?

When using a PIR as an ABSENCE detector as opposed to it's normal use as a PRESENCE detector, there is usually a connection for the push-to-make retractive switch. When you enter the room you press the switch and the lights come on, the pir keeps the lights on whilst detecting movement, if there is no movement after a set length of time (absence time) the lights go back off and you have to press the retractive switch again to bring the lights back on.

This is how the ones I've come across work, think they were made by CP Electronics...

Mike

 

[Evans Electric]

This sounds like the right method to me .

Although why not just use the PIR to detect movement for "ON" and then lack of movement for "OFF" .

 

[adammid]

Mike d- that's sounds like you may have hit the nail on the head. Evans like you say why not just use a PIR for on and off. I am just doing what has been requested.

 

[user 15807]

This is what is in the specification: -

'Switches controlling any absence detection function shall be Retractive and the contractor shall install sufficient detection devices to suit the control requirements.'

Any suggestions?

I read that as, IF there are any switches they must be retractive. Reading between the lines they are asking for automatic lighting that cannot be left switched on (hence request for retractive switches). I would look at providing isolating switch within electrical cupboard for maintenance (standard isolator) then PIR's where required. There appears to be no requirement for override.

If you wish to provide override for a stairwell for example, I would wire PIR's and lights on 3 core assuming T&E, where the 3 core comes back to electric cupboard fit a staircase timer and connect its output to the switched light wire in the 3 core. Any override switches can then be connected to the timer, set the staircase timer the same as the PIR timers to give uniform operation. Now either the override timer or PIR can bring on the lights.

Bloody hell I'm on fire now. Have a look at the GJD sapphire systems, ELV PIR's and a central controller with timer, override and other input options. The kit is quite dear though :-(

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Thinking a bit more, Remember if thats an architect, they pick up good words like "retractive" and spew them out in specs. it might just pay to ask what they want the system to do in detail before trying to design something that they dont realise thay have asked for!

 

[Hayeso32]

As mike d has said, try cp electronics. We are currently installing their system in a school incorporating absence detection.