PRS-002 Placement

[tizwaz]

Hello, looking for some advice to the best place to put a PRS-002 in the lounge. Currently I’m thinking of in the ceiling above the door about a foot away from the wall. So walking into the room will trigger it, but if I’m walking past in the hall and the door is open it shouldn’t trigger as the wall above the door would make it blind at that angle.

Any thoughts or advice regarding my thinking would be much appreciated.

Thanks Chris.

[JonS]

Personally I think putting a device in the ceiling is a last resort (having done it). For just a normal PIR get a standard corner mounted security unit and feed into a digital input somewhere, or home run back to a central point so a future owner could use a standard alarm panel. If you ceiling mount you have to consider making good the fire protection with intumescent back-box, same as you would for a down-lighter.
If you want instant response on entering the room, a wall-switch poistion will be good as would a reed switch on the door. If you go with a wall-switch postion you can later upgrade to a DFP. The idratek PIRs are very sensitive and have a wide angle.
The only advantage a ceiling mounted PIR has is over a sofa where long periods of inactivity can cause the occupancy to time-out if using standard PIRs.
2p

[Gumby]

PIR positioning is a matter of balancing several factors:
i) Avoiding viewing through doors (don't forget the beams can be considered down to floor level, the PIRs are quite sensitive)
ii) Picking up low-levels of occupied motion - eg in bed or on sofa (more common for lounges with open doors) to maintain occupancy
iii) If combined with light level sensor keep away from room lights, especially central pendants.

All my PIRs are in the ceiling, about 2' from the walls, and located roughly centrally in the other dimension, typically over the bed or sofa if relevant. If I was doing it again I would use DFPs in every room at a wall switch position (they weren't available when I did it). The extra cost over PIR+Light+Temp+IR modules is worth it for the much reduced installation time and aggro, let alone the additional features.

As Jon notes, wall mounting is a viable alternative.

As I understand it, the need for intumescent protection to maintain the fire protection level of ceilings is only relevant for ceilings that are considered to be "fire compartments". But regs change and there are also acoustic considerations so you should check yourself. Intumescent stickers are available to fit into standard wall boxes. Interestingly, I came across some building research that found that penetrations through plasterboard ceilings did not significantly effect the fire performance of the ceilings, but who said science should have a bearing on regulations.

[tizwaz]

Hi Chaps, thanks for getting back so quickly. I'd love to go down the DFP option. But having only just scraped through the ‘why can't that ugly piece of plastic go in a cupboard?’ argument with the other half. A DFP would take more persuading energy than I have left.

I think I’m going to put the PRS a bit further into the room and along the wall, so it potentially it’ll be over a sofa or armchair. But not be visible from the hall.

A reed switch on the door won’t work as we rarely close any internal doors. I might try and blu-tac it to the ceiling first to test it’s ‘seeing’ ability.

C.

[chris_j_hunter]

interesting thread ...

extending the question a little, how about multiple PIR situations ...

eg: non-rectangular rooms, rooms with partitions of some sort, or large pieces of furniture, large rooms, or rooms encompassing different zones with different lighting / other requirements (meal prep' & dining, say, or sofas & table & computer corner) ...

having more than one, even more than two, or three, might have advantages in terms of sensing what's going-on ...

but also disadvantages in terms of possible complexity in handling the data & deducing what would be appropriate ...

any experience, any tips, things to avoid, things to be sure to do ????

[JonS]

We have an open plan kitchen, dining, family room but it is zoned for heat and light into 2 Cortex rooms (kitchen and family/dining), so there are PIRs in each mounted more or less back to back on the dividing wall pointing in opposite directions. between these two Cortex Rooms I am about to install a beam-break as a virtual door to help preserve occupancy in each room appropriately.
In quite a few rooms I've mounted additional PIRs as the doors are hung on the "open side" of the door way so the DFP mounted PIRs cannot see most of the room if the door is open, so the additional PIRS are in the opposite corner looking towards the door. No problems with PIRs seeing people in the hall as the door obscures them. The hall is however a single space but long, narrow with the stairs obscuring one end from the other. Ive come to the conclusion that its will be best to split this single area into two Cortex "rooms" (inner and outer hall) and control the lights separately.

So in general
*use multiple PIRs in a light/heat zone where coverage demands it.
* consider virtual doors even if no physical one in large open plan areas where there are differing actvity levels.
*avoid PIRs looking between zones if possible
*If you've got separate lighting for different zones use separate PIRs / Cortex rooms
if that makes sense from a usage view.
* avoid pets as that makes PIR choice and alarm arming more tricky ;-)

HTH

[chris_j_hunter]

many thanks, yep, that helps a lot ...

'must check the range of the PIRs - how far away for them not to see ?

BTW, which beam breaker are you going to use ?

[JonS]

Beam break: http://cpc.farnell.com/_/pem7d/mini-...tem/dp/SR05489
I wanted a retro-reflective one so I only had to power one side of the gap. There is a Velleman kit http://cpc.farnell.com/velleman-kit/...Ntt=beam+break which in theory could be built into a package to be retro-reflective but I decided the pre-packed solution was simpler!

I will surface mount first then see if I can bury in the frame... neatly!
I think alignment will be an issue esp with pets / children around.

PIR range: IIRC most PIRs claim ranges of ~10-15m, but the angular movement across the lens will be constant to get a trigger, so only large movements will be detected at range. Hence to detect shifting in seat / drinking while watching TV needs a PIR close (overhead possibly). I have decided that at some point I will use pressure mats in the sofa plugged into the structured wiring (Cat 5e wall socket) - have to get to point where kids no longer jump on the sofas first to ensure system reliability :-)

[Gumby]

I have decided that at some point I will use pressure mats in the sofa plugged into the structured wiring (Cat 5e wall socket) - have to get to point where kids no longer jump on the sofas first to ensure system reliability :-)

I've been toying with the idea of pressure mats in each side of the bed. My wife has different preferences for night time bathroom illumination to me. It would also e nice to warm the espresso machine up when I get up, which is not necessarily the same as when my wife gets up. Shift patterns complicate automation!

[chris_j_hunter]

'wonder if placing them under-cushions / mattresses would be OK ? ie: slatted bases & helical springs, end-on or stretched, might give an uneven pressure - and so reliability issues & perhaps early failures ?

[Gumby]

I don't think placing the mats on top of the mattress would pass the "Princess and the Pea" test, but equally the weight of the mattress alone would probably trigger the pressure mat anyway. Which is probably why I haven't tried it yet.

I have also considered strain gauges on the slats ... a little more work involved, but could have some interesting applications if an analog value is supplied to Cortex. Eg: Over a certain threshold Cortex announces "no butter on your toast this morning, fatty". Or maybe sets the alarm earlier to ensure sufficient time to cycle to work instead of drive. That would be my side of the bed, obviously ....