Outdoor PIR

some advice please.

This is what I want to happen:
I have a long driveway. When a vehicle or person enters thorugh the driveway, some lights to come on.

Question:
Is an external/outdoor PIR suitable for this, or should some sort of beam be utilised.

ANy of you got experience with this scenario. Your advice would be appreciated.

 

Home on the range

The quick answer is yes you can use a PIR to detect a Car coming up a drive, but the long answer is that there are a couple of provisos and cautions.

1. Range.

The standard Clipsal outdoor PIR (mains powered or C-bus) has a range of 18m, this 18m is determined by a 90kg person walking at >1m/sec ACROSS the PIR field of view and having a >5C difference to the back ground.

So if you point the PIR straight down the drive the car (or pedestrians) will be walking straight towards it and the range will be reduced somewhat (depending on the speed of the target - but for a person walking, typically to 12m)

If you mount the PIR off to one side and effectivly have the target approch across the field of veiw the range will be closer to 18m (from the PIR mounting point)

The PIR will detect targets further away than the 18m if they are bigger, hotter and/or moving faster (ie cars on the road or driving up your nieghbours drive) so you will need to cater for this when working out the mounting position and the the PIR's final aiming position otherwise you may find your outside lights triggered every night as the local bus goes by.

2. Headlights

The PIR has an adjustable light sensor built in that can be set to allow it to operate only when it is dark, at or about sunset or any time light or dark - or any point in between. If you mount the PIR 'looking' down the drive and it is set to only work when it is dark, then when a car approches it at night with its head lights on the PIR may think it is day time and not trigger the load, Again positioning, aiming and light level setting will over come this.

 

Another Question

If you have a long driveway (50 m) and have 5 light circuits (10 m apart) and you want to switch the ligts on as the car approaches ( the light nearest to the car switching on and the previous lights switching off). Would a outdoor PIR do the trick? Or would you need something else? Any ideas?

 

just drive she said

Not with any current C-bus products but with the yet to be released Colour Touch Scrren, HomeGate, Schedule+ and Pascal Automation Controller this would be able to be achieved but (and I know because we tried to do this in ANZAC Parade Canberra where they wanted, at the opening, to have a troop of horse-men ride up the road at the same pace as the C-bus controlled street lights turned on in sequence - couldn't get the horses to match the lights progress) getting the lights to come on (and in your case turn off) at the same rate as various people may drive up or down your drive will either mean that the lights are on/off before or after the car arrives or that they stay on for so long to cope with speed differences that the impact of the effect is lost.

 

We have sucsessfully used inground driveway sensors to achive this effect. Works fine for cars, but not at all for horses To date they have come equiped with little or no metal content.

http://www.drivewayalarms.com/

cheers

 

Clip Clop

What about the horse shoes Ross?

 

Well that was the

bit about almost nil. Besides I mostly have warmblood broodmares, and they have no shoes!

Cheers

 

Your mares could learn something from Imelda Marcos

Your right Ross it's a much better idea to trigger at particular points and drive the lights from those signals than to trigger when a car passes a point and approximate timing from there. There would still need to be an amount of Logic code crunching away in 'something' to make this all happen. And if you were using C-bus a method (probably BusCouplers or General Input Units) to collect the info from your proximity detectors. All this would require an amount of wiring and I guess the appeal of using a PIR is that you mount it locally and the range does the hard work of detecting targets at a distance with no trenches and wires.

 

Uncle, you are quite correct, I used 011011010110100101101110011001000110010101110010 for the logic control. and it worked really well and in either direction, however only as required by the owners (flagged control). The PIR option I've used and still use but there are the obvious limitions in that design.
It was a fun job however.
Cheers