Low power PIR breakout board for Mysensors and evaluation

  • Hardware Contributor


    I like to make my boards small as I can (with my "little" knowledge, lol) and, like lots of you I needed a small, slim and of course low power PIR sensor. I don't like chinese HC-SR504 board because there are big capacitor on it. Not easy to integrate in small enclosure. So I decided to re-design this chinese board with smd capa.
    But, Anticimex pointed to me a very interesting app note : ST AN4368. Thanks to you @Anticimex for your valuable advise πŸ˜‰

    Note : I ordered pcb few weeks ago, it should not take lot of time now to get them. I ordered it at oshpark, as board is small, price is cheap.

    So this board is based on this ST appnote, and especially on the first schematic in it (based on TSU104 opamp, more low power).As app note state, it should be somewhere 23uA. I am using a nanopower nand gate. I didn't find better for this ref..so the board should be 1uA more. I hope it will stay between 23-25uA which is not bad I think..

    I have made few changes for easy testings:

    • 2x potentiometer added
    • debug points
    • optional led on Out Signal (for debug)

    Size : 24x19.7 (mm)
    Components size 0805.

    Now some screenshots:


    Boards can be ordered here : https://oshpark.com/shared_projects/Dc6Tlrt1

    Eagle files and BOM on my git, here : https://github.com/scalz/MySensors-HW/tree/development/LowPowerPIR_Breakout

    So it should work, as I followed app note. Changes I made are minor. And I have taken care of routing to try to not have problem on analog trace...


  • Contest Winner

    Nice! You beat me to it πŸ˜„
    I might do a MYSX module out of it if it turns out to work as good as the app note suggests.

  • Admin


    Which PIR sensor element are you using?

  • Hardware Contributor

  • Hardware Contributor


    I have received pcb. so for the moment it doesn't work like I want. I have not digged a lot. I have just soldered it and powered with two aaa, 3.2v. Led was triggering too much so I checked potentiometers. and it triggers ok but the range is not great for the moment. maybe 2.5m.
    So I looked briefly voltage levels with oscillo and I think I need to check and tune resistors to see if it is about comparator window (resistors), pir sensor or the lens.

    So no good news, no bad news too. it works well at 1m πŸ˜†
    but I have not said my last word πŸ˜ƒ I hope to have some time asap. it would be cool if it worked.

    another thing too: I will update files. not a big mistake but good to know. the silkscreen for the pir sensor is not well oriented.

    Here some pics

  • Contest Winner

    @scalz cool! Nice work. Did you manage to grab some current measurement to see if it operates within reasonable ranges for battery operation?

  • Hardware Contributor

    @Anticimex : hi πŸ˜ƒ
    I didn't checked at first, because I mounted the led. But I just removed it, and here first results with uCurrent:

    • 24uA with no trigger
    • when it triggers it oscillates between 24-27uA. so it seems to work as announced in app note.

    it just needs to check the opamp res divider (3rd stage comparator) I think. Because when I did some tests, looking with my oscillo, voltage levels was moving well when at 3-4m. but it didn't trigger. so I suspect that it needs to refine the comparator window (sensitivity...)

  • Contest Winner

    @scalz that's excellent. I believe you really have something here. Battery operated motion sensing would be awesome!

  • Hardware Contributor

    @Anticimex: yep it would be great. Did you order pcb? if you want I can send one to you with pir sensor and its lens (free πŸ˜‰ I don't know letter postage fee from France to you but it should not be expensive I think.).same offer for you @tbowmo or @Hek πŸ˜‰
    In other hand, I have not enough opamp...and pots so if you have these in stocks..

  • Contest Winner

    @scalz Thats very kind of you, but I am afraid I have not got the time to investigate more closely currently. Little baby present and Christmas coming up πŸ™‚

  • This post is deleted!

  • Hardware Contributor


    just a little update, I made few tests (between two projects 😣 ), trying to see if it could be more low power. And yes it can, it needs for instance to use higher res of course! 10-15M and increasing a little bit capacitors (100nf instead of 10nf) helped to stabilize and I was near 5uA!
    Unfortunately, I didn't had big success with my false triggering...and range increased a little bit, a little bit better too with another sensor (LHI968).

    But that is not my biggest concern here. And I am curious to know what you think. Like you I am searching a low power PIR <10uA, reliable, and not expensive.
    But for low power, we can encounter some case like:

    • holidays : lot of triggering breaking sleep mode and low power.
    • In deepest sleepmode, we have no time reference for blind time etc...
    • So it would require some tricks to handle everything in sketch and finally maybe the overall power consumption would increase a little bit (few uA).

    In other hand, @Myna made a board with E931.96. I don't know if he got it working but I think this ic could solves all this problems.
    MCU deep sleep mode could be possible, and E931.96 could handle false triggering, blind time before retriggering, low power (I think it could equals to my small board), and finally, not the least, it seems that it autocalibrates regarding the sensor. Very interesting in fact! Too bad, it seems it is available only at professionnal supplier.

    So I am asking to professional supplier (Avnet) what could be the availability for this chip. I am already in contact with him for an other interesting chip. It could be great if we could have hand on this ic.
    In the mean time, I have ordered some from aliexpress (I hope it's not clone!).

    That's all. Thanks for reading, and for feedbacks!

  • Hardware Contributor

    Small is small! and more simple πŸ™‚ I will order it at oshpark.

    Component size : 0805
    I hope that will work πŸ™‚ I have ordered the ic at aliexpress. Let's see if it is genuine...if yes, it is not expensive compared to opamp..on the previous board. I am dreaming lol!

    @Hek: I tried to upload another simple eval board at openhardware but I was not able to save/upload it.
    " Unable to save project. Please try again later or contact support."
    So, I will retry later πŸ˜‰

  • Hardware Contributor

    just a very small update to tell I'm pretty happy: I have just received my PIR chips order today (e931). Another thing to do now : a lib and look if it's fake but I hope not! stay tuned πŸ˜‰

  • Scalz, which news about e931 ?

  • Hardware Contributor

    I will post some news soon πŸ˜‰ multiple things in progress (hw & sw) but now I'm better organized to speed up my dev in my hobby time lol

  • You shut down work on TSU104 version?

  • Following this thread with interest! Keep up the great work! πŸ‘

  • Hardware Contributor

    yep for the moment, I have a lot of e931 to use. but I had some ideas for the tsu104 so I will look at it later but don't know when yet (at the end of my todo..)

  • @scalz said:

    I will post some news soon πŸ˜‰ multiple things in progress (hw & sw) but now I'm better organized to speed up my dev in my hobby time lol

    I was just thinking the other day, is there any sort of post already going around here like "show off your workbench / work area?"

    I am getting ready to purchase my initial supplies and some small cabinets, soldering station, etc. which will be, initially, pretty meager but I thought it would be fun to show off my little area, and I'm sure some people here have much more impressive work spaces that I'm sure many would be interested in seeing. πŸ™‚

    If not, I think I will create one eventually, when I get my area set up. πŸ™‚

  • Hardware Contributor

    @TRS-80 ahah πŸ™‚ I thought about this too but I need to clean my lab! too much jumble 😊

  • Mod

    @TRS-80 said:

    show off your workbench / work area?

    Bit old, but still fun: http://forum.mysensors.org/topic/229/your-workshop

  • Admin

    Still missing a picture of yours!

  • Hardware Contributor

    I'm in the middle of the schematic and parts design for my current project: http://forum.mysensors.org/topic/3449/homini-complete-room-sensor-module.

    I'm very interested in the motion detection going on over here, where are you at currently with this development @scalz?

    1. Would you recommend this for my motion solution, but obviously i'm looking to have this on-board my PCB rather than a module. Unless i decide some change in my initial enclosure design. I could have this mounted as a daughter/riser card on a header.

    2. Is there any compromises on this board compared to normal motion detection due to its low power consumption or have you just worked wonders and got the power consumption down with no trade-offs in functionality?

    3. What're your specifications on this board? I'm interested to know your current test results in terms of Power consumption, desired supply voltage, detection range (Would it detect from sitting on the ceiling any movement coming into the room/floor level of around 3m?).

  • Hardware Contributor


    1. not easy question...I would like to have done more tests and tune on the first schematics but when I saw a lot of e931 at ali I wanted to to try this as it was a little bit easier (or not! needed a lib). but there is a big cons on e931. first is not easy to source..and at mouser no stock and not so cheap. So If I would dig in again, I think the app notes described is nice, can be improved..
    2. all worked as described πŸ˜‰ e931 or appnote. Appnote can be few uA too, just needs care and tests. It can be used in more different ways too as it's analog, it doesn't need an mcu to work, if well tuned πŸ˜‰ like in common pir for instance.
    3. I have been able to go as low as 5uA with appnote (with component I had in stock). but I have not ran lot of tests to compare all configuration lens (small or common), different pir sensors (I have cheap chinese, and a little bit better LHI...). Could be lower like maybe 1-2uA I think.

    I don't remember, how will you power you project? ac or batt? which kind of batt?

  • Hardware Contributor


    Okay, well i've been looking at this PIR but the price is a little high and tbh although i know this module is not going to be THAT CHEAP, i would like to keep it airing on the lower sides of things with the amount of things going into this module.

    I do plan on powering it via AC mains. This is a HUGE step for me as i've never made a AC-DC converted PSU before. But its time to learn!

    The small amount of testing you have done looks interested to be honest. I just wonder if it worth going to that extent to put into this. I'm kind of feeling using the HC-SR501 module as a daughter board or even just copying the circuitry onto my board like your original idea here.

  • Hardware Contributor

    I would advise you same thing. but maybe hc-sr501 could be enough?? imho you don't need a 1uA thing if you will power it via AC. If I would use AC, this is what I would use I think. Plus, if there is other bigger power hungry sensors, maybe the pir is nothing vs them..

  • Hardware Contributor

    @scalz, I have tried to keep everything pretty low on power consumption with the components that i have chosen. This is costing me a little more than the higher powered components and no doubt, causing me some hard work when it comes to integrating it all together but i feel that the long road that it will go down will be worth every minute with people onboard to develop this module. I'm yet to see something else on the market like this, the only thing is the popular NEST protect products and the FIBARO Smoke detector, which isn't as 'clever' as this hopes to be.

  • Hardware Contributor

    Hello @scalz did you have any positive result with e931 ?

  • Hardware Contributor

    if i remember well (it's a while), i had things working but not finished to write the lib for it (read&write to it with a serial protocol, one wire only, not the OneWire protocol).
    But then i moved to a lower power solution with my low power multisensors rev1.
    Since i've changed a little bit my stuff for handling PIRs for lowering cost of the circuit, but still low power, and sensitivity & triggers count should be "tunable".
    I also stopped working on e931 because it's exotic and not really available ic, apart from very special suppliers which are mostly interested by big batches.
    Do you know where e931 can be ordered?? (don't tell me avn** lol, i already tried to negociate but were not so much interested in osh..)If so, I could take a look at what i did, when more time, as actually my new version should be lower cost i think.

  • Hardware Contributor

    @scalz ok thank you for your answer. I saw the link on AliExpress is not active anymore so yes it seems pretty hard to get for quantities lower than 3000 πŸ˜„

    Found 2 websites selling them in small quantities but I don't have so much trust...
    (<1$) http://www.dmelechips.com/index.php?route=product/product&product_id=2116
    (2$) http://dwmzone.com/en/e-components/293-e93196-ultra-low-power-pir-controller.html

    I just wanted to know if it was worth trying to follow this path if real life testing of AM312/612 is still disapointing, but it seems it's not if you have a cheaper solution with widely available parts.

  • Hardware Contributor

    oki. well this is mostly because for the moment i would like to have a PIR with as less part as possible and for 2-3.6V range.
    but i'll take a look at my old work asap πŸ˜‰ as i already have the boards, and a few e931 in stock.

  • Hardware Contributor

    @scalz if you have no time in the coming weeks can I buy you a board + e931 ? I can give you an address to send it in France and my friend will bring it back to Vietnam in August. I used to be a software developer so I can probably try something on the com with the e931 πŸ™‚

  • Hardware Contributor

    @Nca78 cool! been a sw dev too, in IT, before hw πŸ‘
    oki i'll tell you what happens (i'm gonna try this w-e, or today don't know), or maybe you should wait a little bit i show my new boards. Perhaps you'll be interested who knows.. πŸ™‚ I had no problems with comms though, i didn't polish my code that's all. I also made a PIR helper for Mysensors.

  • Hardware Contributor

    @Nca78 i didn't forget what i said πŸ˜‰
    Here, from the logic analyzer, a screenshot of my lib refactor for e931.96. Write (2nd row) and read back (1st row) : ok
    just a few things i would like to check, and i'll release the lib, as this chip will be optional on one of my new boards.

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