Instructables

DIY Driveway Alert System Problem

I tried to make a driveway alert system, but it has a problem. I connected a walkie-talkie to a Radio Shack PIR Sensor using this reed relay.

Essentially, when the PIR sensor detects motion, it outputs 5 V which triggers the reed relay and closes the contacts, which connects the two contacts on the walkie-talkie button, which sends a beep to the other walkie-talkie.

Problem: It works as planned, except that after the motion stops and the reed relay disconnects the walkie-talkie button, it will inexplicably re-connect the walkie-talkie button after about a second, and will repeat this cycle of beeping every couple seconds indefinitely. The strange thing is that sometimes it will work just as it is supposed to, but other times it wont.

Other details: The PIR sensor is powered by a 9 volt fed through a 5 V regulator so it gets steady voltage, while the walkie talkie is powered by the regular AAA batteries. I am a novice with electronics, so don't rule out that I may have made a simple mistake.

Try just triggering the radio with the relay (blip the relay with a battery) does the problem happen then ?

The PIR needs a separate transistor to drive a relay.