Multiple PIRs connected to single control timer box

[tomtomato]

Hi,

I would like to install multiple PIR detectors in a large residential car park, and control them all through a single control box/single timer (to switch about 20 fluorescent tubes at the same time).

The PIRs will be hard to access, and therefore it would be better to adjust the delay in one single location.

Is there such solution available, where the PIRs don't have built-in timers?

Thanks,
Tom

 

[PrenticeBoyofDerry]

I think a little more detail would be required to satisfy your question.
If you want timed lighting, why are PIRs required?
Are you wanting motion sensors only to operate at a certain time or times?
Or just lighting on when the desired time/times is/are reached?

 

[tomtomato]

It's for a large car park, so I would like all the fluorescent tubes to turn on when motion is detected (car or pedestrian) through a number of sensors, and to stay on for a given duration (for instance 2 min) after the last mouvement was detected.

Thanks,
Seb

 

[PrenticeBoyofDerry]

Is this function required during daylight hours only or constantly?

 

[tomtomato]

It's an underground car park, so lights would need to come up all day.

 

[JohnW2]

I would like to install multiple PIR detectors in a large residential car park, and control them all through a single control box/single timer (to switch about 20 fluorescent tubes at the same time). The PIRs will be hard to access, and therefore it would be better to adjust the delay in one single location. Is there such solution available, where the PIRs don't have built-in timers?

That's all quite do-able. Details obviously depend upon the actual devices used but, conceptually, you basically need to put all the (non-timer) PIR detectors in 'parallel', use the output from them to drive a standalone timer unit (plenty available) and then (in view of the size of the load) use the output of the timer to driver a relay or contactor which powers the lights. The electrician installing it ought to be familiar with all this.

However, how often do you contemplate these lights going on and off? Frequent switching of fluorescent tubes plays havoc with their life expectancy.

Kind Regards, John

 

[tomtomato]

Thanks.

The car park has 35 cars, so on the assumption that each car travels once a day, the lights would be switched around 70 - 80 times a day.

If the timer is set on 2 minutes, and there is no motion detected after 2 minutes, the lights would stay on for 4 minutes x 80 = 320 minutes, instead of 24 hours a day, so a saving of 72% of electricity.

 

[Iggifer]

leaving and returning would make it more like 70-100

 

[JohnW2]

The car park has 35 cars, so on the assumption that each car travels once a day, the lights would be switched around 70 - 80 times a day. If the timer is set on 2 minutes, and there is no motion detected after 2 minutes, the lights would stay on for 4 minutes x 80 = 320 minutes, instead of 24 hours a day, so a saving of 72% of electricity.

I wasn't suggesting that it won't save electricity, but fluorescent tubes may well not last long with that number of on-off cycles - you might ultimately want to consider some different type of lighting. You might possibly also want to consider including a timeswitch to over-ride the PIR switching so that the lights remain on continuously during periods (at the start and end of the day) when there are likely to be a lot of car movements,to reduce the amount of switching. Don't forget that there's the hasle of changing the tubes (and perhaps even labour costs), as well as the cost of buying them.

The 4 minute estimate/guess obviously depends upon how long the movement lasts - the lights would remain on throughout movement and until 2 minutes after it ceased. I also suspect that you may be underestimating the number of cycles. Many people (particularly 'Mums') may well make a lot more than one journey per day. There will also presumably be issues of movement of people as well as cars - unloading a week's worth of shopping from Tesco could involve several activations of the lights.

Kind Regards, John

 

[Iggifer]

i think I would be more inclined to go with timed push switches at each entrance, cheaper and will eliminate unnecessary activations

the only problem with this is, you will need to set them long enough so people don't get plunged into darkness on the way back from their car

the extra time though may reduce the number of activations

 

[JohnW2]

i think I would be more inclined to go with timed push switches at each entrance, cheaper and will eliminate unnecessary activations. the only problem with this is, you will need to set them long enough so people don't get plunged into darkness on the way back from their car

I'm not so sure about that. Unless the lights stayed on for a long time, it could result in convenience, if not also safety, issues - underground car parks are likely to be incredibly dark, particularly at night.

As for how long the light would have to stay on if one did do that, I don't know how typical she is, but my wife is quite capable of staying in her car for 10 minutes or more after she's parked - listening to the end of a radio programme, 'sorting her handbag' or, worst of all, if there's someone with her, just chatting!

Kind Regards, John

 

[Iggifer]

As for how long the light would have to stay on if one did do that, I don't know how typical she is, but my wife is quite capable of staying in her car for 10 minutes or more after she's parked - listening to the end of a radio programme, 'sorting her handbag' or, worst of all, if there's someone with her, just chatting!

Yea, not married so didn't consider that! Sounds reasonable though.

I retract my advice.

 

[tomtomato]

I would still need some PIRs when cars come in, in addition to push buttons next to each entrance.

The idea was to place about 6 PIRs on the car park, so any motion within the car park would reset the timer.

I have been told before that fluorescent tubes will be damaged by frequent switching cycles. However, I have seen many underground car parks with fluorescent tubes and PIRs or push buttons with timers.

Even if this shortens their life, they may last as long as if they were always on, and the electricity savings are massive, but tubes are quite inexpensive.

 

[JohnW2]

I would still need some PIRs when cars come in, in addition to push buttons next to each entrance. The idea was to place about 6 PIRs on the car park, so any motion within the car park would reset the timer.

I suspect that it was being suggested that it could be done with no PIRs, so even incoming drivers would have to press some button but, for reasons I've given, I do not think that would be a very good idea. Multiple PIRs seems to be the sensible approach.

I have been told before that fluorescent tubes will be damaged by frequent switching cycles. However, I have seen many underground car parks with fluorescent tubes and PIRs or push buttons with timers. Even if this shortens their life, they may last as long as if they were always on, and the electricity savings are massive, but tubes are quite inexpensive.

I think its inevitable that frequent switching will shorten the life of the tubes to at least some extent but, as you say, the financial benefits of electricity savings are very likely to swing the balance in favour of switching. However, as I said, there are factors other than the cost of tubes involved. Are the tubes all easily accessible for changing (e.g. not above car parking bays)?

To be able to properly make the decisions, you would really need to do a 'survey' of car park usage. If it transpired that there are periods (e.g. at the start and end of the day) when the lights are on 'almost continuously' (but with multiple on/off switching cycles) for an hour or two, then, as I said, it may make sense to add a timeswitch to over-ride the PIRs (and have the lights on continuously) during those periods. That would be very simple, and would cost little more than the price of a cheap timewsitch. If it were a '7-day' timeswitch, it could also take into account the different usage at weekends (when there probably are not any particularly usage-intensive periods, so PIR-control alone would probably be appropriate).

Kind Regards, John

 

[RF Lighting]

This sounds like a GJD system would be ideal