PIR Sensor: false positive detections

Fozi

@zoltan Really nice build!Congrats!
Yeah, a low-pass filter can solve the interferences from the WiFi module, too, of course. But due to my lazyness and impatience I sacrificed an old VGA cable and re-used the ferrite bead:beaming_face_with_smiling_eyes:

MZ-BER

Hey folks - thanks for your answers. I decided to goahed with a RCWL-0516. But have the same issues. I’m testing the sensitivity with a python script. I also covered it in alu foil - no change. Now I ordered a ferrite beat and will add to the cables (around all of the them or only GND, 5v or Output?)

I’m also thinking about adding a low pass filter, but I have no experience with that. Where do I have to add that? GND & Output?

Fozi

@mz-ber Just put all wires through the bead.
With the RCWL-0516 you should note that they can be very sensitive (up to 7m on free sight) and detect motion even through walls. First I went the alu foil route, too, but then modded my RCWL-0516 with a trimmer. Now the mirror is triggered when I approach the mirror less than 1m. Check the link in my signature for details, if you like.

MZ-BER

@fozi Yes! I followed your instructions in detail - that was very helpful. And yes, I noticed how sensitive it is. In your tutorial you removed the the tiny SMD resistor soldered and replaced that. What if I just remove it and not replace it. Is the range than completely gone and doesent work anymore?

MZ-BER

Hi @zoltan - I was reviewing your tutorial. Really good documented. I have a question about the wiring drawing you shared. I’m new to it and dont understand everything. But I’m a fast learner :-)

In your drawing you added a couple of symbols. I guess these are resistors and filters, right?

Numbers 1, 2 and 3 look similar, only with a diffrent capacity. Is that a Capacitor?
What are 4 and 5? Is that a conductor? What capacity is here needed?
And number 6, not sure. Is that a RND or a resistor?

Fozi

@mz-ber If you remove the resistor completely without any replacement the sensor won’t work any more.

thgmirror

Didn’t I said, I’m not an electrician?
It is not a step-down/up … it is called Pull-Up, resp Pull-Down.
Please see here for detailed (german) explanation: https://www.elektronik-kompendium.de/sites/raspberry-pi/2006051.htm

MZ-BER

@thgmirror Yep, that is what I’ll do next. Already ordered a starter kit with resistors, inductors and capacitors.

I also noticed, even if I added the ferrite beat, that the sensor recevied every minute excact on the second a signal

Fozi

@thgmirror said in PIR Sensor: false positive detections:

It is not a step-down/up … it is called Pull-Up, resp Pull-Down.

Are you dealing with 3D printing? Just asking, because step-down converters are quite popular for modding cooling fans in that hobby :beaming_face_with_smiling_eyes:

thgmirror

@fozi no, currently no 3D-printing, but may be in the future:-)

Zoltan

@mz-ber
Apologies for the late response
1, 2 and 3 is capacitors yes
4 & 5 is inductors or coils. The rule is a Capacitor conduct high frequency but block low frequency. The coil or inductor is doing the opposite, and conduct low frequency but block high frequency. The whole idea is to short circuit any spikes on the power line as well as the data line to ground. This is quite a big low pass filter and you can make it smaller with less components.
Remove 1
Leave 4 & 2
Replace 5 with a wire

6 is a resister yes. 10 Kilo Ohm 1/4 watt is perfect

The coils you can strip out of an old circuit board. If it looks like a wire wind coil and it measure less than 3 ohm then its perfect

Zoltan

@mz-ber
The controller board with the low pass filter