What is my wireless PIR receiver trying to tell me?

[Simon]

Hello - I've got a couple of these wireless PIR receivers

which periodically exhibit strange behaviour. Sometimes, when one of the transmitters they have been paired with activates, instead of switching on the load circuit, the receiver just flashes its red LED 5 times. I know that the receiver is recognising the transmitter to some degree, because it doesn't flash its LED in response to transmitters that it hasn't been paired with.

Any guesses as to what the 5 flashes might mean? Something like "I've just heard from transmitter X, but there was some interference, so I'm not sure" perhaps. I think the unit operates on 433MHz which I understand is quite crowded, but I'm not convinced the problem is interference. The manual doesn't help. I've tried contacting the manufacturers, but haven't had a response. I also tried taking it apart to see if there are any subassemblies that I could look up datasheets for but it seems to be entirely bespoke.

Thanks

[Peter Crosland]

These items are notorious for their susceptibility to interference for alls sorts of things. The problem is that the receivers in them are poorly designed and don't reject unwanted signals. The frequencies around 433Mhz are full of all sorts of radio frequency devices from car keys to amateur radio transmitters. What has probably happened is the device memory has become scrambled. Try removing the battery for a couple of hours from transmitter and receiver and then see if it is cured. You might not need to do it for so long if the device does not retain its memory when the battery is removed.

Peter Crosland