, which caused a heated discussion and many questions. Well, since there are a lot of questions about the repair of motion sensors, I decided to put them in a separate article-continuation.

The most important thing I want to convey is that the main thing is not to be able to solder and check the integrity of the elements. The main thing is to be able to think logically and critically, to explore, to analyze. And gain experience.

There are many motion sensor circuits, but the principle is the same. This principle and much more regarding this device is given at the link at the beginning of the article, once again I recommend studying it and comments on it. The same article provides links to other articles about motion sensors, you can download instructions and datasheets for the details of the sensor's electrical circuit.

So, I will give the most popular motion sensor circuit once again:

This scheme was sent by my regular reader Alexander from Korolev in December 2014, for which many thanks to him again. I will rely on this scheme in the text of the article, since it is the most typical. It should not be confusing that the circuit in our example will be scattered over two boards - low-current and power.

At the end of the article, the revision of this scheme will be given.

Now I am publishing a photo of the motion sensor boards, which were sent by my other reader - Renat.

Low current motion sensor board

Power board (power) motion sensor

Here is our correspondence with Renat:

Renat: Hello! According to the diagram and description, I have the same sensor, I don’t know the exact model, they asked me to look at “stopped working”. Stopped at the power board. I checked all the elements, after the diode bridge + 24V comes out, the zener diode gives out + 8V, soldered the second part of the circuit (the board where the IR receiver, microcircuit, etc.). And now, I can not understand why the relay is activated when I apply voltage?