PIR/Microwave sensor

[PeterC]

I need to put one or two outside lights for a friend. I know the luminaires (down-facing so no dazzle) and lamps (wide-angle R63 LEDs) but I'm fed up with PIRs that turn on the light when it's not even properly dusk. I looked at some microwave ones and there seems to be a problem with leaves etc. when windy and lots of spurious switching. PIR would be OK if I could get something decent - don't mind the price within reason. Need 180 deg./hemispherical; might want to use just one on the corner of the house. Any ideas, please?

[Brian Gaff (Sofa]

In a way then, you need two sensors. One that enables the unit to be switched on but the lamp will operate only after a certain light level is reached. A simple photocell system, and a pir to allow movement to be detected when in the range and override the manual switch, but only when dark. Brian

[Brian]

They normally have an adjustable light sensor. We had one I fitted in our previous house - perhaps 30 years back - I can?t believe they haven?t improved since then. The light sensor works with the PIR and it only turns on the light below a preset level and if someone is within range. It was pretty good. We lived on a main road, people on the foot path didn?t trigger it etc and after dark it would still work if a car passed as you walked towards it.

Just look for a sensor which combines PIR and light sensing which is adjustable.

[Chris B]

Like this one

[alan_m]

Every light That I've seen with a inbuilt PIR has had a dusk to dawn facility that is enabled by adjusting a light intensity setting. Lighting during the daylight hours could also be achieved by setting the adjustment to one end.

[PeterC]

Mine have the light sensor and they're set to the lowest position yet still they come on far too early (by light). As I said, they come on too soon in the evening, even from new. That's why I would appreciate advice on those that do not. Mine are from TS and looked good on 'paper' but still are silly. Some say about 3 lux but I don't know how light that is One has a passing speed range starting at 0.6 m/S, so 'creeps' can bypass it!

[PeterC]

Civil Twilight is 3.4 lux, so I guess that the light coming on whenn there's still useful light in the evening is reasonable at 3 lux rating. Oh well...

[Martin Brown]

Some of them come with a darkness setting for when they will activate. Perhaps most of them do but clueless installers often test them in daylight and leave them in the will switch in daytime state.

Read the spec sheet and you should be able to find decent PIR switches that do have an adjustable ambient light threshold.

Many solar powered garden lamps have this problem too since they were designed for much lower latitudes where it goes dark quite abruptly. Our long summer twilight confuses the hell out of them.

[PeterC]

Both of mine and also those that I've fitted over the last 30 years, are adjustable for light and all have been set to Min. light as soon as the angle and time have been set. What is bloody annoying is that often the pots are not accessible when the PIR is pointing at a suitable angle (both of mine are about 80 deg. down from horizontal), so it's necessary to reset the angle and then check after dark. Almost all I've seen in the sheds and on line are adjustable, down to about

3 lux - still quite light at that level and not needed. I guess it's due to cost of good sensors (rather like LCDs on 'stats, thermometers etc. are still poor quality, grey screens as the were 30 years ago.

[jkn]

Can't you partially shield the sensor so that it is less sensitive?

I seem to recall reading about people doing this using strips of black tape alternating across the surface of the sensor window. Not sure if insulating tape would work, again IIRC it is transparent to IR, but something like that...