PIR sensor died on LED floodlight

[r-p]

I should be able to figure this out, but am lost for the moment.
Any experts on here? I do not have a working scope at the moment, but have plenty multimeters.


Replaced the actual infrared sensor on the PCB, but the overall issue (not shutting off once triggered) is still happening.

Here's the reverse engineered schematic. Let me know if I should clean it up.



The IR sensor is on the edge of the paper on the top. It gives off a pulse when something is detected. (Top left opamp)
Sens is the potmeter for the sensitivity. (bottom left opamp)
Lux is a potmeter to determine at what ambient light it should start to work. (Pulls down the output of the PCB when it is too light?)
Time is a simple RC time constant which feeds the top right opamp which feeds a relay on another PCB. (bottom right opamp)

I am running the PCB from a stable powersupply (7V) instead of its own AC-DC PCB (makes 20V for the 24V relay and 8V for the opamp).

When stuffing the whole PCB into a stainless steel double walled insulating cup and measuring the output of the bottom right, it retriggers irregularly every few seconds. So it is logical that the floodlight never turns off.

Any clue where I should look?

[redwire]

Re: PIR sensor died on LED floodlight

It looks like a vanilla PIR sensor circuit.

Check the DC power supply you are using is quiet and earth grounded and you did ground your metal cup to it? If is it a 2-prong PSU then hum and noise can cause false triggering.

PIR sensors have cheap electrolytic capacitors, I would replace them all. It's the main reason I find these go wonky.
You can use a multimeter and check if the PIR or the light sensor is doing the false triggering.

There are many schematics on the web if you search "pir sensor lm324".

[budm]

Re: PIR sensor died on LED floodlight

Watch out for some of the so call circuits out there, for example:
http://8085projects.info/lm324-based...h-circuit.html
http://www.8085projects.info/image.a...20circuit..jpg
See U1-3 Input pins 9 & pin 10 are tied together, R12 and R13 are not doing anything.

[budm]

Re: PIR sensor died on LED floodlight

This one is from PIR Mfg. App circuit.


https://cdn.badcaps-static.com/pdfs/...4dcbb3885f.pdf

[r-p]

Re: PIR sensor died on LED floodlight

What's a vanilla pir ? I get tons of dirty download links when I google that

I will have a look at the electrolitic capacitors and compare some more schematics of circuits. I found a few before, but adding LM324 ups the useful hits a lot!

Thanks!

BTW, the powersupply is not grounded during testing but is a laboratory power supply that should be stable enough, especially compared to the transformerless capacitor/resistor network that normally powers the circuit. Will make sure to plug the PS into a grounded outlet next time. The floodlight itself is grounded but only to the housing, but again have not tested this in a grounded outlet since replacing the PIR sensor (D203S).

[fzabkar]

Re: PIR sensor died on LED floodlight

"Vanilla" means "generic", "jelly bean", "ordinary".