Outside PIR puzzle

[Tim+]

I went out to get firewood a few nights ago and my PIR triggered outside lights just kept blinking intermittently as if they were failing to “latch on”.

Ordered a new PIR switch but before it arrived I found that the lights seemed to be operating normally! That was until last night when it was distinctly colder, and once again the lights were blinking and not latching on.

Is it likely that temperature is making them intermittently faulty? Is it likely that the faulty one might be repairable?

I’ll be replacing with the new one anyway but if I can mend the old one I could reuse it elsewhere.

FWIW, it’s one of these.

Tim

[alan_m]

The PIR probably will also have a light sensor so the light doesn't come on in daylight.

I have had a couple of dusk to dawn lights with similar light sensors and I've found that in low light conditions (dusk) that there is zero hysteresis in switching and at the light/dark switch threshold the lights can flash on/off for few minutes.

When you experienced the flashing could it have been the light sensor enabling/disabling the PIR in a dusk type situation?

[Tim+]

Plausible. I’ll do more testing at different light levels.

Tim

[SH]

Are the lights LED? Due to a failing PSU, they can start blinking like disco lights.

Bypass teh PIR by switching to permanent live, do the lights still blink? If so replace the LED light.

If you leave it, it will eventually fail completely.

[Animal]

The 2 most unreliable parts are joints & electrolytic capacitors. Caps rise in ESR a lot as they get cold. So that would be the first thing to look at.

[Tim+]

No, the lights work fine at other times (like tonight well after dark). I’m beginning to think it is to do with the low light sensor. It’s possibly set just too low.

Tim

[Brian Gaff]

Yes I had flashing lights when a police car was parked across the road with its flashing light on. It looks like short term hystoresis is not working the way its supposed to.

Brian

[Tim+]

Well I fitted my new PIR and had a look inside the old one but there were certainly no defects that were visible.

Tested the new PIR after nightfall and it clearly clicked when I passed it but no light!

Of course it was nothing to do with the PIR directly, just a loose connection in the lamp housing that it was connected to. Doh!

Anyhow, now I have a “spare” that I can use to replace the duff one by the garage (that really is duff, I think….). ;-)

Tim