SR-602 PIR sensor not working. Ideas ?
Good day folks. I'm trying to build a motion-activated light for my front door.....sounds simple enough. I had two SR602 PIRs on hand in my parts bin which I got for a similar project that never happened, so I thought these would be perfect to use here. They don't seem to work though. Either I'm doing something wrong or they're defective in some way...
I power the sensor with a 12v wall-wart and use an SB8050 transistor and a 200ohm resistor between the collector and the "out" pin of the sensor to switch a 12v relay on and off....simple enough. It works, so there's nothing wrong with my circuit, but the problem is it keeps cycling on and off forever. What I did, according to the documentation, I changed the 0-ohm resistor to 56k to give me an on-time of around 11s. It's not perfect, but it's close enough - it's within a 2-5s error up or down, but that's acceptable. The problem is once the time elapses, the output pin stays low for about 2 seconds then comes back on by itself, again and again.....what gives ? I thought this may be like a "setup" time, but I left it alone for a good 5 minutes and it was still doing this.
I tried the other sensor which I hadn't altered in any way and it's doing the same thing, except in smaller intervals, since it's still got that default 0ohm resistor for the on-time, so it comes on for 2 seconds, then off for 2 and so on...
The strange part is that it only seems to do this when it's got the transistor's base connected to the output ! If I remove the resistor and let the output pin float, it works fine, as my multimeter shows !
I tried adding some capacitors on both the output and the VIN pin, I even put a diode between the output pin and the transistor, but nothing helped ! It simply won't stay off for longer than 2s !
Any suggestions, including some "better" small form-factor sensors ? Size is an important factor, since I could just run down to the local store and get one, but those are massive in size for my project !
I power the sensor with a 12v wall-wart and use an SB8050 transistor and a 200ohm resistor between the collector and the "out" pin of the sensor to switch a 12v relay on and off....simple enough. It works, so there's nothing wrong with my circuit, but the problem is it keeps cycling on and off forever. What I did, according to the documentation, I changed the 0-ohm resistor to 56k to give me an on-time of around 11s. It's not perfect, but it's close enough - it's within a 2-5s error up or down, but that's acceptable. The problem is once the time elapses, the output pin stays low for about 2 seconds then comes back on by itself, again and again.....what gives ? I thought this may be like a "setup" time, but I left it alone for a good 5 minutes and it was still doing this.
I tried the other sensor which I hadn't altered in any way and it's doing the same thing, except in smaller intervals, since it's still got that default 0ohm resistor for the on-time, so it comes on for 2 seconds, then off for 2 and so on...
The strange part is that it only seems to do this when it's got the transistor's base connected to the output ! If I remove the resistor and let the output pin float, it works fine, as my multimeter shows !
I tried adding some capacitors on both the output and the VIN pin, I even put a diode between the output pin and the transistor, but nothing helped ! It simply won't stay off for longer than 2s !
Any suggestions, including some "better" small form-factor sensors ? Size is an important factor, since I could just run down to the local store and get one, but those are massive in size for my project !
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