Connecting a 240 V PIR motion detector to a Raspberry Pi

Question

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

Inside its plastic case I found two PCBs. One is the power supply board which has a 24 VDC relay, an S9013 NPN transistor, some blue resistors, two small zener diodes and one bigger one, a big red film capacitor (CBB22/630V334J), a smaller one (CBB22/630V223J), a gray film capacitor (222/1200V), four 1N4007 diodes, two electrolytic caps (220 μF/35V, 100 μF/25V), one small ceramic capacitor, two big gray resistors (?) and three wires (red, blue, and brown).

The other board contains the PIR sensor, an S9013 NPN transistor, a lot of blue resistors (?), a UTC324D IC, five electrolytic caps (1 μF/50v, 10 μF/50V, 100 μF/16v, 100 μF/25V, 47 μF/25V), four small ceramic capacitors, three Zener diodes, three potentiometers for adjusting SENS, TIME, and 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 three wires. How I should connect these three 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 3.3 V as it is? The UTC324D datasheet says that it can work with supply voltages between 3-32 VDC 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 12 V? I have seen a tutorial about wiring an external motion detector to 12 V, but the author of the article had a 4-pin board and I don't know how to wire it.

Some photos:

Answer 1

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.