PIR question.

[ss]

I am hoping to use a cheap PIR to monitor outdoor activity at night, but the one I have appears to be too sensitive, it doesnt have the usual adjustments so may try and block some of the lense range. Anyhow I opened it up and there is a sensor and then an LED `bulb` which comes on when activated. Is the LED light necessary for it to operate as I would prefer it didnt light up if someone is snooping around my back garden at night.

It is a wirless battery operated cheapo whereby the sensor is in the garden and the receiver is wireless in the house.

[Dave Liquorice]

Probably not but what does "... there is a sensor and then and LED 'bulb' ..." really mean? I read it that they are in series so simply sniping a leg of the LED would stop it working.

However I suspect the sensor is connected across +v and gnd with an out put that goes high for a second or two when triggered. The LED is between output and ground, possibly via a resistor, sniping a leg in this case will just disable the LED.

Think I'd have a switch of some sort (twisted wires...) so the LED can be enabled to facilitate a walk test. Though if the Rx is battery powered you could just carry that.

[Brian Gaff (Sofa 2)]

No need for a light unless it has a camera that needs the light. Normally the leds are infra red. I think the Ring Door bell uses infra red leds. Brian

[Tricky Dicky]

I would check your receiver on our wireless alarm the panel illuminates each time a sensor is activated wether armed or not, so a useful way of checking it is working or if the battery is flat. Other than that without the led in the PIR you have no quick way of telling. I only have a PIR in the garage but find it reassuring to see it flash each time I enter the garage. As for intruders seeing it I think few will even notice unless looking directly at it. You are more aware because you know it is there.

Richard

[Martin Brown]

No the LED is to indicate the thing has triggered. A spot of black paint will stop it being visible whilst retaining whatever IP rating it has.

Be aware that it will trigger on spider inside or bats flying close to the sensor as well as rats, cats, foxes and badgers at increasing range.

A wildlife PIR triggered camera might be more useful for your application - that way you have some video of the scrotes.

[T i m]

<snip>

I was going to investigate a(n invisible?) break-beam sort of device that could be set higher than most ground dwelling creatures and below the typical flight line of a bird. That connected to a GSM SMS dialler so that I can 1) remotely view the CCTV then 2) potentially call the Police.

Nothing the Police like to know better than the scrotes are still on the scene. ;-)

Cheers, T i m

[Andy Burns]

dual (modulated) beams are supposed to be best for least false triggering.

[T i m]

Funnily enough, that's the sort of thing I built for BIL's Arduino-automated Model Railway project, the sort that wouldn't be 'confused' if the were in view of another transmitter etc.

It's just that they were for very short distances, not sure if they would cope over 5m or so (especially if reflecting from the other end)?

I have seen such used across driveways where people might regularly use them to turn round (near a school possibly) where they make an audible alarm to indicate to people 'I know what you are doing'.

Cheers, T i m

[whisky-dave]

I'd just stick a bit of blu-tak over it and try it out.

The sensor might be triggering via daylight, as xmas is coming you'll probbly have plenty of quality st./roses semi-transparent sweet wrappers you can use to cover the sensor to make it less sensative.