Function of photocell on operation of PIR?

All of the fixtures that I have seen that are motion only, do not have a photo cell. Sort of dumb turning on a light in the day time. My porch fixture has a photo cell and motion detector. I do not have a adjustment on the photocell. I try to keep the sensitivity down so that anyone on the sidewalk does not trigger it. A couple of steps into the yard and it will turn on. I leave the fixture on all of the time so in the evenings when it starts getting dark the motion sensor takes over and will turn the light on according to my settings.

I too thought a daytime lamp was silly but it works rather well:

When the PIR is tripped, the unit makes a loud sound. If you plug a lamp into the mains socket on the unit then power is sent to that socket. You might have a red bulb in your study and get a visual alarm that someone is approaching. Could be useful if you didn't want them to hear the audio alarm.

Sounds a bit like mine. What do you find the photocell does to the PIR's ability to sense people in different conditions of ambient light?

The unit I describe sounds more of an alarm.

Your unit lights a lamp and seems more as a warning to intruders or a courtesy to visitors.

The photocell is nothing to do with varying the sensitivity of the device - it is there to detect 'darkness'. Commonly these things are arranged so that the pir triggers a lamp of some for some fixed time, to illuminate a path for example, but such illumination is not required in daylight. The position and direction of view the photocell (most frequently actually either a photo-resistor or a photo-transistor) depends on the combined optical characteristics of the housing, lensing, and photo device. Pointing down is the most common way of getting the best average ambient illumination level. Pointing up almost never is.

I think you may have skipped too lightly over where I say that the motion detector unit is designed for 24 hour operation so clearly the photocell is not for sensing darkness for "night time only" operation.

I have to ask why do you say that the photocell cannot be to detect light or dark. you say that it is 24 hour operation. All pir operated lights are for

He never said it was a PIR operated light.

In fact I assumed it was part of an alarm system.

are for

These normally have the photo cell, to allow an _option_ to control a light. I have a couple of controllers of this sort, that feed an alarm, and one of the configuration options, allows a light to be triggered at night....

Best Wishes

Excellent point (I just assumed that it was a light) as most outside motions are.

Although the photocell is still probably to >

By operate an alarm I assume that you are referring to some kind of chime system rather than an Intruder alarm.

This sounds like a unit that I have. It can be set for motion activation and/or darkness. For some strange reason, the manufacturer didn't see the need to incorporate a daytime inhibit on the motion detector.

Why would you need a pir that did not detect in the daylight? You may need a pir that does not turn on a light in daylight hours but why inhibit the pir function?