3V battery for door sensor node.



  • Hi all, Happy New Year too! 🙂

    So I am trying to get the door sensor to fit in a smaller box and that means getting away from 2xAAA batteries for something smaller.

    Does anyone have any suggestions on what might be suitable?

    The node has 2 sensors, anti-tamper microswitch and magnetic contact switch. Both are enabled on interrupt and the node spends most of its time asleep. I would expect 1-4 door openings a day and maybe a heartbeat that sends battery level to the controller hourly or with even longer sleep times. It has 3.3v promini with low power bootloader, nrf24l01+ (with ceramic cap), regulator and both leds removed from pro mini. Pretty much as per the battery page and door window sensor page with just the added anti-tamper added.

    Would you think that 1 or 2 button cells (with either 2x1.5V in series or 2x 3V in parallel)? CR2032 / CR2025? Or maybe the CR123 3V cell?

    I would like to get at least 6 months from a battery if possible - a year would be fantastic!

    Any thoughts or experience out there that might help with this please?



  • @skywatch said in 3V battery for door sensor node.:

    CR2032

    if you power everything directly from 3V battery and run arduino at 1MHz, CR2032 battery should last more than a year (or even 10 years).



  • and set bodlevel to 1.8V



  • @rozpruwacz

    Thank you for the fast reply! 🙂

    I have already set fuses for 1.8V brownout but read somewhere that 8MHz actually uses less power than 1MHz as the 'time alive' sending data is 8 times longer at 1MHz and therefore uses more battery (the clock has no bearing during sleep it seems?)....

    Do you (or anyone) have any thoughts on that?

    Thanks


  • Mod

    @skywatch the reason for running at 1MHz is that the atmega328 is only rated for 8MHz at ~2.4V and above (see graph in the datasheet). So the atmega328 may malfunction somewhere between 2.4 and 1.8V.



  • @mfalkvidd

    Good call! - Yes I had forgotton that (to much festive spirit)! - Thanks for the pointer.

    So the next question then is would it be better to use 1MHz and connect direct to the batteries or would it be better to run at 8MHz and use a boost converter to 3.3V? By 'better' I mean longer battery life 😉

    Thanks



  • In your scenario the most power hungry module is the nrf24 module when it sends data. I don't know how mysensors handles this but I believe that the time that nrf module is in the send mode does not depend on the arduino clock because nrf module has its own clock source. Someone correct me if I'm wrong.


  • Mod

    @rozpruwacz yes that sounds reasonable.

    @skywatch a really good booster should work, but most cheap ones draw way too much power when there is no load, which will drain battery while sleeping. Check the datasheet for "quiescent current".

    As an example, ADP1610 uses 1-2mA with no load❗



  • Thanks to you both! 🙂

    I was thinking of using these....

    https://www.ebay.co.uk/itm/Mini-DC-DC-0-8-3-3V-to-3-3V-Step-up-Boost-Power-Module-Voltage-Converter-Arduino/272665263182?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

    I have these already for other things, but I will look into measuring the quiescent current (my old fluke meter won't go down to the levels of nA).....Maybe I will get find a histab resistor and put it in series with the supply positive and see what voltage I get across it on the meter or scope. A little Ohms law and I should be done!

    It's taken a long time - but I am getting there now! 🙂


  • Hardware Contributor

    @skywatch said in 3V battery for door sensor node.:

    I have already set fuses for 1.8V brownout but read somewhere that 8MHz actually uses less power than 1MHz as the 'time alive' sending data is 8 times longer at 1MHz and therefore uses more battery (the clock has no bearing during sleep it seems?)....

    Do you (or anyone) have any thoughts on that?

    My experience is it's not true when using NRF24, especially with "switch" sensors taking no time for measurement and needing no complex operation/calculations. Most of the time active is when sending data through the radio, and frequency of atmega doesn't change sending speed of the NRF24. And if you have radio link problems and your sensors has to resend message a few times, then it's better to save a few mA by running at 1mA all that extra time.
    It seems it's a different story with RFM radios though, that's why other users using those radios here or on other forums seem to favour the 8MHz option.

    @skywatch said in 3V battery for door sensor node.:

    So the next question then is would it be better to use 1MHz and connect direct to the batteries or would it be better to run at 8MHz and use a boost converter to 3.3V? By 'better' I mean longer battery life 😉

    Do not use a boost converter, even the very good and expensive ones consumes a few uA, and if you optimise your sensor that's more than what it will consume in sleep. In addition they create noise and decrease the radio performance and stability of the node. Just use one CR2032 it lasts a very long time with basic sensors, my temp/hum sensors with si7021 are on the way for something like 2 years of battery life, and my door sensor with NO/NC reed switch will probably last 3 years.
    Using 2 CR2032 in parallel is a bad idea, it seems the one with highest voltage will try to "charge" the other. Then its voltage will lower below voltage of the one it's trying to charge and the will switch the "charge"/discharge positions until they are completely depleted.

    Just use one CR2032 and apply the following things to make it last :

    • put a capacitor in parallel, 100-200uF ceramic (real capacity nearly cut in half due to voltage bias) or 100uF electrolytic (but it has more leakage)
    • add short sleeps between radio TX/RX sequences, so your battery can "rest" and recharge the capacitor. You can look at what I did in the scripts for the NModule TH/Door sensor board on openhardware.io, it might not be perfect but it works for my sensors.

    This is necessary because lithium button cells have a high internal resistance and their voltage drops quickly when you apply a high load. CR2032 can only sustain 2mA so the capacitor is needed to help it power the radio (15mA). Without capacitor a lot of energy will be wasted as heat and you will only be able to use a fraction of the real capacity of your battery.



  • @Nca78

    Thank you for taking the time to post that and help me out - All posts here should be a reference for the current 'best practice' for battery powered nodes!

    I was just looking at the chip on the boards I posted (ADP2018A) - and whilst advertised as 'low quiescent current' devices, I guess that 'low' is a subjective term!

    All you said makes sense, so that is the route I will go. Now I have to find the battery holders......they're here somewhere! 😉

    CHeers and Happy New Year. 🙂


  • Hardware Contributor

    Hi,

    of course I agree with all comments above. imho 6months, even a year is too short for maintenance..

    Regarding frequency, in general, the radio modules run their own crystal so they can't be very impacted on their side by changing 1/8mhz (or maybe spi comm, but that's not the case here, this is usually working).

    But MySensors lib "could be". I'm not saying it will!
    As changing freq can also change some timeout, delays etc in the lib. So far there is no time slot syncing mechanism, which wouldn't help at all here..
    So that may depends on features needed (just thinking to delays in radio drivers for collisions, signing, heartbeat etc when it's about a main door node), and may or not add some nacks, then more transmit, more power etc..


  • Mod

    @scalz wouldn't we have problems already today if that was the case? MySensors is used on 8 and 16 MHz atmega328 (and 1MHz with sensebender micro) and on 80 and 160 MHz esp8266.


  • Mod

    If you have enough room, I'd go for a LiFePo4 battery and no need to change clock and fuses or use any buck booster


  • Hardware Contributor

    @mfalkvidd as long as there is no precise timing involved in lib, this should be ok. who can do more can do less. well this is always good to remember 1mhz mode is not as precise vs 8/16Mhz or faster espressif.

    There is another point I'm thinking, when it's about security nodes, lowpower (like a main door node for example). When using 328p deep sleep without time, you lose the watchdog feature. I think, in general, for a reliable security node, wdt may be a good idea to prevent any lockup (especially when using cheap, outofspecs ?? 328p clone??).

    Sure it's important to optimize runtime power consumption, but in case of a node which doesn't wake up often, the most important point to improve for lifetime is the sleep power consumption of the device.

    I agree with gohan for lifepo4, too bad there are not lot of variants yet.
    I think there are no definitive answer for lowpower node and batt lifetime. It depends on the device requirements, always compromise. As a primary lithium AA/AAA+booster will always last a lot longer than a coincell. But that needs nano quiescent current with high efficiency during lightload boosters that you won't find already assembled at aliexpress, +filtering (depends on the part but doesn't hurt)
    AA/AAA compromise is a bigger profile than coincell, or need more parts so more expensive for example. Here I guess, a lower profile is needed for a door node.


  • Hardware Contributor

    @scalz said in 3V battery for door sensor node.:

    But that needs nano quiescent current with high efficiency during lightload boosters that you won't find already assembled at aliexpress, +filtering (depends on the part but doesn't hurt)

    Any good suggestion for that ? I'm making a breakout for TPS61098 to test, but if you have other suggestions of similar chips I'm interested 🙂


  • Mod

    I still believe a 2€ LiFePO4 battery is the cheapest solution 😄


  • Hardware Contributor

    @gohan said in 3V battery for door sensor node.:

    I still believe a 2€ LiFePO4 battery is the cheapest solution 😄

    Where do you get it at this price ?


  • Mod

    look for soshine AA batteries on aliexpress, I paid 8€ for 4 AA batteries plus 2 connectors


  • Hardware Contributor

    @gohan said in 3V battery for door sensor node.:

    look for soshine AA batteries on aliexpress, I paid 8€ for 4 AA batteries plus 2 connectors

    Yes I have those, paid more as shipping was expensive. But they are too big 😞


  • Mod

    @nca78 I think if you go for a slimnode solution (on openhardware) it is not very big



  • Good topic. I have been lazy since a month to ask the same question regarding best batteries do people use for battery powered nodes ?

    I have thought of using AAA batteries but I really do not know which categories do I go with. Lithuim or Alkaline ?

    If you check this link https://d2ei442zrkqy2u.cloudfront.net/wp-content/uploads/2016/03/MN2400_US_CT1.pdf

    You find that the Alkaline battery can operate till it reaches 1.0 v for more than 1200 service hours. So two in Series will give me 2v which are still above 1.9 for the atmega and nrf to run.

    But also if you check lithuim batteries.
    http://data.energizer.com/pdfs/l92.pdf

    It also operates for 1200 service hours at 1.4v before the battery dies quickly.

    My question. Why would I choose a more expensive option (which is Lithuim) although I can use the Alkaline which is much cheaper and may be half the price ? Will the performance is better with steady voltage using lithuim ?

    Thanks.


  • Mod

    @ahmedadelhosni with most low-power nodes, we're talking >10,000 service hours. With those low drains, the self discharge of the battery becomes much more important than how much they can deliver at 1mA drain. Unfortunately, neither of the datasheets you link to contain self discharge. I don't know why they don't include it. The ENERGIZER L92 specified a shelf life of 20 years though.

    https://en.wikipedia.org/wiki/Self-discharge#Typical_self-discharge_by_battery_type lists typical self discharge for some battery types though. Lithium-metal is better than alkaline batteries, which is better than (rechargeable) Lithium-ion which is better than (rechargeable) NiMh.

    In short, yes it is probably better to choose a Lithium battery because the alkaline battery will have self-discharged after ~5 years while the Lithium battery can go 10 (or more).


  • Hardware Contributor

    In addition to what @mfalkvidd said, when you use nrf24, the lower the voltage the lower the emitting power, so the quality of your radio link can decrease and you can lose messages, meaning your sensor could appear unreliable or have to resend the message a lot a lot meaning shorter battery life.

    But if you have a really low power node you will have a very long battery life (2-3+ years) with standard AAA so I would go for a good quality alcaline (not a cheap one to avoid leaks ruining your sensors). And if you see you have range problems when voltage goes lower then switch to lithium version.


  • Hardware Contributor

    @Nca78

    Any good suggestion for that ? I'm making a breakout for TPS61098 to test, but if you have other suggestions of similar chips I'm interested 🙂

    I was thinking to these boosters. They are nice, I used them in a old multisensors project I showed here.
    Hmm.. it's not at all handsolderable, what happens ?! 😜
    I'm kidding 😉 I'm the same, I don't like to be limited by parts choice.

    This booster is very small, but 6 pins only if i remember. better use good parts, good shielded inductor, good planes etc to reduce emi, improve efficiency etc.
    I moved to different battery types because I wanted more discrete nodes, or simplicity, and between AA/AAA there is not a big profile difference. But I still have a recent design with this booster, for a usecase.


  • Mod

    @scalz you forgot to add some links 😄


  • Hardware Contributor

    @gohan which links ?


  • Mod

    @scalz said in 3V battery for door sensor node.:

    TPS61098

    where you referring to this booster? I thought you were talking about another one you had


  • Hardware Contributor

    @gohan
    yes these one; I have different variants but the family is TPS6109x.
    I made a multisensor two years ago with this booster (published a preview in the forum). works well, but finally I published an other multisensor, which was cheaper, on coincell. But still not enough cheap for people 😉
    Now I prefer to have just a few projects&revisions, than too much. to save time and support. So I carefully sort my stuff 🙂


  • Hardware Contributor

    @scalz said in 3V battery for door sensor node.:

    This booster is very small, but 6 pins only if i remember. better use good parts, good shielded inductor, good planes etc to reduce emi, improve efficiency etc.

    Yes I sticked to what is suggested in the datasheet and bought everything from arrow. But in the end it takes more space than expected so I'm not sure I'll make the board...


  • Hardware Contributor

    @nca78 said in 3V battery for door sensor node.:

    Yes I sticked to what is suggested in the datasheet and bought everything from arrow. But in the end it takes more space than expected so I'm not sure I'll make the board...

    yep it was another point i forgot to mention..



  • Thanks for all the input and ideas - I'll go with cr2032 and see how it goes. Batteries, holders and ceramic caps are all on their way, so time will tell on this one.

    Thanks all! 🙂


 

285
Online

7.6k
Users

8.5k
Topics

91.3k
Posts