Looking for reliable PIR human detection sensors

  • Hi all,

    I have huge problems with PIR human detection in my smarthome.
    The sensor is mounted on the ceiling in my corridor. If I walk up stairs then the detection is very very bad. (similar to an back and forth movement)
    Some other articles also confirmed that these kind of sensors do have such problems. Sidewards movements (e.g. left to right) seems to work much better.
    Unfortunately Repositioning the sensor in this case is nearly impossible.

    I already tested different kind of sensors like:

    • HC-SR501
    • AM312
    • IKEA Molgan

    Do you have any ideas / experience with better human detection sensors?

    • Is AM612 better than AM312?
    • RCWL-0516 microwave radar sensor --> Possible false detection through walls?
    • Thermal IR Arrays like Panasonic AMG8833 or Omron D6T --> expensive

    Or do you think that it is cheaper to use an "Aeotec Multi-Sensor 6 (Zwave)".
    This sensor costs about 50-55 Euro. For example the price for an IR Array sensor starts at around 20-30 Euro.

  • the cause of the problems You have lais in how the PIR sensors works. They work by comparing heat readings in different zones of their view. The zones are 2-dimensional, so this is why they work ok, when you walk sideways and not very good when you walk towards them. Nothing You can do accept using a pir with beter resolution. Or, You can make a node with two pir sensors in different orientations.

    I used HC-SR501 and AM312. AM312 that is available as a whole module has shitty lens, but with correct lens it works as good as HC-SR501 and AM312 can work with lower voltages and has much less power consumption. So I would go for AM312 with good lens.

  • The radiowave based ones are imo better wrt. that, so why not give them a try?

    According to my experience results depend much on the environment, especially wrt. their ability to "look" through walls. If it's bricks without holes, you may get also satisfying results.

    Besides all other things a stable power sourcing seems to be essential . I use 5V, but some report also satisfying results when sourcing the IC directly with 3.3V.

    There's the option to reduce responsiveness also by adding a resistor, more details can be found here.

  • @rozpruwacz I also already thought about making a node with multiple PIR sensors in it. May you know if it is possible to connect the OUT pin of multiple PIR sensors to the same input pin on my micro controller?

    @rejoe2 Have you already made some experience or used these microwave sensors as motion sensor?
    They are not so expensive so I already ordered them. Waiting for delivery now.

  • @ehome for sure it is possible to connect them, to single pin. The circuit will depend on the pir internals. It may be as easy as just connecting the wires toghether. I will check it for am312 when i get home.

  • @ehome said in Looking for reliable PIR human detection sensors:

    @rejoe2 Have you already made some experience or used these microwave sensors as motion sensor?

    I use several of them on a couple of RS485 MySensors nodes and also know some others in the FHEM forum using them with ESPEasy. So as far as I know the most common problems with the RCWL's are power-related (ESP8266 is a 3.3V-device).

    As I have some problems with my RS485 setup the following is somehow preliminary (seems the 12V to 5V conversion is root cause; this also affects the RCWL's):
    The ones I use myself are in my cellar and in the garage (two rooms in the later). In the cellar, detection is indirect (PIR on same wall as entrance door): Works very well, but also detects the opening of the door from corridor towards a second cellar room - there's a small hole in the wall between these two rooms near the PIR's position... So motion is also detected when just passing the cellar.
    In the bigger garage room, it works perfectly - when there's enough power for the entire node - the converter on the pro mini seems not to supply enough power to get the RS485 chip working sufficiently in all situations. There it's placed on a side wall - no detection, when passing outside, but opening the front door is detected pretty reliable, in some cases, one has to do one step into the garage, detection angel is 80+ degrees .
    The third RCWL I only recently installed, so there's not too much enough experience to talk about, the others are up and running for months now. But at least the radio fields of both RCWL's in the neighbouring rooms in the garage seem to not influence one another I had some doubts on that point as I first tried to use 3 of the RCWL's on the cellar node to monitor the two cellar rooms and the corridor; that didn't work - as I now think due to powering issues.

    I did some experiments wrt the resistor placement, but by now, all are just without one (but I can also state: one can see a difference)

    So keep us updated once the parts you ordered are up and running!

  • @ehome as I looked at am312 datasheet I didn't find any information about its output pin. So to be on the safe side, I would connect the two sensors trough additional n-mosfet transistor. So connect output of each pir to the mosfet gate. And then sources of both mosftes connect to ground and drains of both mosfets connect togheter to the arduino input pin. You will also need a pull-up resistor (external or arduino internal).