Arduino with built-in RF running on a single AA



  • Hello,

    I've just found this project: https://www.kickstarter.com/projects/340271897/whisper-node

    Looks like the board is very similar to the Moteino, another Arduino Clone... but looks like it also runs with very low power, like a single AA. My idea is to have a board like that and use it together with sensors (temp/humidity/presence) and as a smart switch, to control things remotely. I really liked the idea of running on normal (cheap) Alkaline batteries (not li-po)...

    This still a Kickstarter, does anyone know if there's already exist a similar board available on the market or should I go for it?

    Thanks


  • Hardware Contributor

    excellent! looks like my project here http://forum.mysensors.org/topic/2951/my-mysx-multisensors-board
    But mine use a more efficient/low power stepup especially for light loads, radio on top, signing and sensors... ;) (but the stepup I use is smaller so not handsolderable...). I don't see on their boards a connector for the aa cell too... Seems I should have done a kickstarter too lol!
    but no matter, if you want to run your node on one AAA/AA or two in // you would need stepup so it's a nice alternative board, not so expensive, cool :)



  • Nice.. you project looks really cool! I didn't understand much about the step-up you are using. You mentioned 2x50mA, so do you use one output for the radio module and the other for the MCU or simply put both outputs together? believe a RF transmission + MCU would bit very close if not over that, no?!

    Are you producing any prototype? Do you have any idea if it will become a product some day? :smiley:

    I'm asking that because I'm really after something like that, but this Kickstarter project was the closest I can get... everything else uses an el-cheapo LDO regulator. I never got anything from Kickstarter before, don't trust very much. I think for the price worth trying.

    Danke!


  • Hardware Contributor

    for the stepup, you can use 1x100 on one rail or 2x50. in fact it can handle higher current spikes. Atmel+sensors I use does not use so much power, and radio is 30-40max, depending of its config (I will try to use RX pwm sleep mode to be able to have reception in sleep mode, and atc lib for rfm69 which can reduce powr consumption too by managing RSSI. I won't connect more things or maybe a door reed switch so I should not have extra consumption.

    On my protoboard, I have smd jumpers for options if I want all on one rail or separate radio on one rail and sensors on other rail, ldo or not etc..
    Unfortunately, still proto for the moment (need to check my pir lib timings on scope etc...). I have actually only few pcbs but if all is good I will order more (sell small batch for friends if I have time as now I have my reflow oven, and I'm still searching the best way to provide it if needed...)

    The board you pointed is very nice. If I wouldn't have my boards I would be tempted too. But it is low power as long as you have nothing on it!! Each time, add things it will break low power. They use a MCP16xx step up, and in datasheet they don't say anything about efficiency for consumption < 1mA. Trust me if it was 90%eff at 10uA..they will say it, "here is an ultra low Iq High eff step up" blabla...So the more few uA added in sleep mode the more uA the step up will use (x2 maybe x3 here!). I don't say it's not a good board at all!! just there are things good to know. A board is low power depending on what you do with it. Still the same thing, choose carefully what you connect to it (same thing for me too!).

    For remember, theoretical power consumption formula is like this:
    Consumption_at_input = (Vout_Booster x I_consumption_circuit)/(Vin_batt x Efficiency_for_vin)
    Example : batt = 1.2V, booster output=3V, everything on circuit consumes in sleep mode says 10uA, and in datasheet, for instance for my booster, Efficiency is 85% at 1.2V vin for a 10uA load
    So : power consumption is (3V*10uA)/(1.2 * 0.85) = 29uA!
    Imagine if the step up is 60 or 70% eff at 10uA...But in other hand, you can use only one AA! very easy to source, lot of power, and compared to 2xAA in series, if instead, you put them in //, you double your autonomy :) One AA is 2500-3000mA, I prefer lithium if the node is optimized ;)
    Welcome to Mysensors :)



  • Thanks again, learned a lot... I decide to give a try there, I also had a look on some components' datasheet and seems to be what I need... Let's see, if end up getting the boards I'll publish a review here later.


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