Battery life for Motion Sensor

  • New to Arduino!
    I have built motion sensors following the example found on the site, based on Arduino Nano. I want to power them with a 9V battery.
    After a few days, the remaining voltage is 5.56V and the sensor does not detect any more the movements. Plugged back on my laptop, everything works well. Back to the battery, no detection.
    Is there something to do in the software, beside the sleeping time parameter to increase the life time of the battery. My last attempt is to push the sleeping time to 600000 ms. Waiting to see improvement
    Thank you for any help.

  • Hi!
    Sorry to say, but the Arduino Nano may not be the best choice for battery operation and maybe the Motion Detector also is not the most power economic application. I guess, to start with you have not done any modification to the Nano like removing the power LED? There goes a few milliamps the whole time.

    The PIR need rather high voltage to be stable and not generate random detects. I run mine on 8V. But the Nano needs only 5V so you burn off a bit of power in the voltage regulator chip, even if the sleep current of the Nano is very low. Of course, the more detections there are, the more power is used during the day.

    The Arduino ProMini is a better choice for battery operation. Please see Battery Powering in the left-hand column on the MySensors site. There are a few tricks there to really bring down power consumption. Then again the PIR needs more than 5V so you will have to use a power booster if you use the ProMini 8 MHz version that runs on 3.3 V.

    I think sleeping for 600000 mS will only marginally improve battery economy. I went through the same ordeal as you and I run my Motion Detector on a 9 V wall-wart.

    For sensors that really work well on battery I would suggest Light, Temperature and Humidity. I have a few of these built around ProMini 8 MHz and they typically run for 9 months or more on 2 x AA reporting every 2 minutes, but if you look at the link above, people achieve much better results. But I'm happy with 9 months.😀

    Best of luck and keep experimenting!

  • Admin

    You should also have a look at this thread on how to modify a commonly used motion detector to run off 3v3.

  • Hardware Contributor

    And use 2xAA instead of 9v 👍

  • @bgunnarb Thank you for your quick answer! I have to investigate Arduino Mini (Uno was my first choice, apparently wrong). I really need to operate those sensors for a one year period without replacing batteries, and having a wired power (5V from AC 220 does not seem to be a viable solution).
    I'll keep working on it.👍

  • @hek Interesting but may be a bit too complicated for my knowledge level. Thanks👍

  • @sundberg84 Noted. Thanks👌

  • Mod

    There are also am 312 pir sensors that work at 3.3v, but the have some blind spots. Or just buy the xiaomi gateway and motion sensors if you don't want to modify things, since making something battery friendly means removing all those components that consume energy.

  • You can also use 3 AA batteries in a configuration like this:

    I have noted values for rechargeable batteries as these have a nominal value of 1.2 volts vs 1.5 volts for an alkaline battery. The 4.5v side would be to power the PIR and the 3V side to power the pro mini.

  • @gohan Thanks for the info, but I would like to build my own sensors. So i'll study the Pro Mini on 3.3V further.

  • @popsyann and get yourself a good current meter. It is almost imposible to make low power node without the current meter.

  • @rozpruwacz What do you mean by "good current meter"? Can you be a bit more specific? Have some knowledge of electricity and electronics domain but that does not ring a bell to me. Thanks in advance for your answer.

  • @dbemowsk Thank you for the info. I have made some progress and I have one sensor working on Pro Mini, with 2 x AA batteries. I am facing an issue with radio range. Apparently everything works well within close range but if I put the sensor some 8-10 meters from the gateway, I do not have accurate update of the sensor state (on-off). I though the NRF24 was able to cover such range.....

  • Mod

    Use a multimeter that can measure uA or build your own (there is a project on openhardware).

    If your nrf24 are clones it is normal, also the material of your house affects range.