I want to connect a 240V PIR motion detector directly to my Raspberry Pi 3.

Inside its plastic case I found 2 PCBs. One is the power supply board which has a 24VDC relay, a S9013 NPN transistor, some blue resistors, 2 small zener diodes and 1 bigger one, a big red film capacitor (CBB22/630V334J), a smaller one (CBB22/630V223J), a gray film capacitor (222/1200V), 4 1N4007 diodes, 2 electrolytic caps (220uF/35V, 100uF/25V), 1 small ceramic capacitor, 2 big gray resistors??? and 3 wires (RED, BLUE, BROWN). The other board contains the PIR sensor, a S9013 NPN transistor, a lot of blue resistors ??? , a UTC324D IC, 5 electrolytic caps (1uF/50v, 10uF/50V, 100uF/16v, 100uF/25V, 47uF/25V), 4 small ceramic capacitors, 3 zener diodes, 3 potentiometers for adjusting "SENS, TIME, LUX" and a photoresistor (which i removed for another purpose and I can't find it, but I think it works without it).

The board with the PIR sensor is connected to the power supply board with 3 wires. How i should connect these 3 wires to my Raspberry Pi 3 in order to get the PIR sensor working? Do i have to remove something from the PCB? Is it going to work on 3.3v as it is? The UTC324D datasheet says that it can work with supply voltages between 3-32VDC so this is not a problem.

If i can't connect it to my Raspberry Pi, can you tell me how I can make this work on 12v? I have seen a tutorial about wiring an external motion detector to 12v, but the author of the article had a 4 pin board and I don't know how to wire it.

Some photos:

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  • \$\begingroup\$ Have some components been removed from the PCB with the relay? \$\endgroup\$ Apr 23 '18 at 18:20
  • \$\begingroup\$ Yes, I removed the bridge rectifier and some other components as i have seen in a Youtube video, but the board presented on that video is a bit different than mine. I can resolder everything back if it is necessary. \$\endgroup\$
    – devlime26
    Apr 23 '18 at 18:36
  • \$\begingroup\$ I would be tracing out these PCBs to draw a schematic. That will make it easier to figure out which parts aren't necessary. \$\endgroup\$
    – user253751
    Apr 24 '18 at 0:09

There are three wires going to the detection board. It is very likely that there are two power lines (0 V and 12 V) and a signal for when something has been detected.

Your task is to trace the circuitry to figure out which is which. If you have a pinout of the IC then it should be fairly easy, but do remember you're looking at the IC upside-down from the bottom of the PCB.

If you can, confirm that any other devices (such as the IR detector) can work at 12 V. That's so that nothing breaks when you supply the board with 12 V. A voltmeter connected between the remaining wire and 0 V will tell you what voltage it gives out when it is idle and when it is activated, so then you can figure out if you need a simple voltage divider made of resistors to connect safely to the RPi, or if something a bit more complex is needed.


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