Thanks to the wonders of the Arduino, there are a load of useful electronic modules available on ebay at ridiculously low prices. You don't need an Arduino to use many of these devices, so here's how you can add a buffer transistor to a PIR module to let it switch strings of battery operated LED lights.
The typical quiescent current of these PIR modules is just 50uA (50 micro Amps) so they will run a VERY long time on a set of rechargeable cells before they need recharged. The time they last depends on how often the lights are triggered.
This allows the possibility of an outdoor Xmas tree in the middle of nowhere that turns on whenever anyone walks near it and then turns off when they leave. Add a solar panel to top up the batteries and you could have a very low maintenance decorative effect.
As mentioned in the video, the modules may have a movable link that can switch between two modes. retriggerable and non-retriggerable. In non-retriggerable mode the lights will turn on for a fixed time and then turn off again even if there is continuous movement, but then re-trigger again for another time cycle. In retriggerable mode the timer keeps being reset every time movement is detected, meaning the lights will simply stay on while someone is in the vicinity. the retriggerable mode is the best in this application, and is set by default on many of the modules.

16 thoughts on “How pir modules work and using them to control led strings.”
  1. Avataaar/Circle Created with python_avatars 家榮 吳 says:

    It can prevent working accident.

  2. Avataaar/Circle Created with python_avatars All Dave says:

    Ofcourse when I'm looking for something obscure like this you've done a video on it😂

  3. Avataaar/Circle Created with python_avatars H2 O says:

    Thank you. You are sharing your knowledge.
    I made your project. It was very nice. but there were interesting findings about the battery. I work with 3 types of batteries. I tested lithium watch batteries which are 18650, aaa battery, 3v. With the only 18650, the sensor burned itself. I connected 2 in series from a 3v Isha lithium battery (makes 6 v), the sensor lights up on its own. there was a problem. It worked without any problem in 4 AA batteries and it works well. Can you explain the logic of this error in a simpler way? I am very curious. Is there an imbalance in voltage?

  4. Avataaar/Circle Created with python_avatars Jonny Garland says:

    🤔👌👋👍

  5. Avataaar/Circle Created with python_avatars Dugmer Junction says:

    Evening, I’m trying to use MP2307 Adjustable Mini360 DC-DC Converter Step Down Buck Voltage Regulator but I’m getting lost as on your diagram only one wire come out the bottom, but on my regulator there are two outputs, can you offer any help? Happy to put a video up on my channel if needed

  6. Avataaar/Circle Created with python_avatars sean nguyen says:

    Hi sir
    Thank you for your interesting video and I am thinking applying it for my car. How is schematic looks like to use 12v car battery as a source to drive a horn (similar car's horn) as a siren?
    Thank you in advance for your advice.

  7. Avataaar/Circle Created with python_avatars Gary says:

    Excellent tutorial anyone who didn't study electronics will find this informative. These pir modules didn't exist when I studied, shows my ancient age.

  8. Avataaar/Circle Created with python_avatars David says:

    If I have a few scrap Blue ray drives, Could I somehow take a car dash cam and incorporate I wonder & then incorporate it with a telescope to make night vision? Probably not thermal?🤔🤔
    I hate wasting things in this throw away world "as you know". Anyways No need to answer but this has peaked my curiosity so much more!!

  9. Avataaar/Circle Created with python_avatars Mike says:

    Have you tried those microwave based motion sensors?

  10. Avataaar/Circle Created with python_avatars Scott Hather - Music, AI art & stuff says:

    I watch your videos regularly, but it's very handy to dip into "classic clive" from 7 years ago. I bought my first PIR module (noob alert) and confidently wired it to my ESP32 microcontroller. It detects movement ALL the time. Thought it was a dud, but MAYBE it just needs the transistor you mention in this video, as the ESP32 must be fluctuating quite a bit based on what I have already connected to it, the voltage/current to the PIR must be all over the place…I shall experiment!…BUT NEVER EXPERIMENT WITH 240V…again. Glad I didn't throw it away, it may work perfectly fine with the correct knowledge!

  11. Avataaar/Circle Created with python_avatars Rich_Lex says:

    Just the circuit I was looking for. 👍

  12. Avataaar/Circle Created with python_avatars THE 101 CHANNEL says:

    I have been experimenting with logic level mosfets with these PIR sensors due to low current output but they usually didn't work for me , my only option was to use arduino to trigger a transistor but with this circuit design you have made my day sir.. I guess there always is something to learn after all 🙂
    Thanks a lot again for sharing and making the world a better place , at least for me 🙂

  13. Avataaar/Circle Created with python_avatars Ho wong says:

    What type of NPN did you use?

  14. Avataaar/Circle Created with python_avatars danny jensen says:

    I really enjoyed this video.

  15. Avataaar/Circle Created with python_avatars Alex says:

    Might be possible to use only three nimh batteries by bipassing the 3.3 voltage regulator inside the pir, and soldering a wire directly from the battery pack to the pir 3.3v pad

  16. Avataaar/Circle Created with python_avatars Joseph Friend says:

    Hi, great video, I've got an led strip in a display case which looks great now. However the motion sensor is a little unpredictable. Any thoughts on why this is happening. Also I'm using 9v instead of 5v in the video do I need different resistor values?

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