Thank you for your answer. I was just curious about whether there might be a technical reason behind the choice. And even with Arduinos there are a lot of sophisticated projects possible, I did make some of them myself. Just because something is newer and “more modern” doesn’t neccessarily mean it’s better.
And I see how this tutorial might be more about the sensor than the microcontroller used. So just let me remark this: the sensor can be used with Arduinos, too, and even the code is basically the same. So just pull one out of your box of odds and sods, and go for it 🙂

Hi.
This is just a basic tutorial to show how to interface this kind of sensor.
The idea is to use it in more advanced projects. Not just use it like this…
Regards,
Sara

Firstly, there is no LDR pin, in places where the LDR pin is referenced, it should read as CDS pin. The voltage across the LDR could be read at the CDS pin.

Secondly, the C-TM description is unclear. I think the device outputs a 2 second high pulse on OUT when motion is detected. Adding a capacitor on the C-TM terminals would change that time, probably increase it.

Why?