๐Ÿ’ฌ My Slim 2AA Battery Node





  • Iยดve read about your battery node with great interest. Nice work! Do your nodes keep their meshing capability after you put them in sleep mode?


  • Mod

    If you mean a repeater node (https://www.mysensors.org/download/sensor_api_15#create-repeating-nodes ) the answer is no. The radio is shut off during sleep so it can not receive. For a repeater node you need a permanent power supply.



  • Thats what I suspected. Thanks for quick response.



  • Hello :)
    In the BOM file there is C5 capacitor, but I can't figure out where it does stand on the board. Can you help please ?



  • @carmelo42 Hi, I have not (yet) built a "Slim 2AA battery node" so I'm afraid I'm not the right guy to ask. Good luck though.


  • Hardware Contributor



  • thanks @m26872 :)

    I have ordered smd capacitors for c5 ... but I think it will be good :)

    Can you explain the role of the C5 cap ? I know that C4 is for decoupling for the radio, but C1, C2, C3 and C4 : I don't know !

    Another little question :)
    with my brand new atmega328p, I have burned the bootloader with an arduino uno with the "ArduinoISP" in it.

    After that, I have sent the sketch with another arduino (with it's own atmega removed) and my brand new atmega like that :
    https://www.arduino.cc/en/uploads/Tutorial/ArduinoUSBSerialSimple.png

    Is it possible to put the sketch in the atmega directly on the slim2aabatterynode board ? With an FTDI serial device ?



  • Keep in mind that if you are trying to use a DHT11 or DHT22 attached to the Slim 2AA, it only seems to work with 8 or 16MHz.. I couldn't get it to work with the ATmega328 running at 1MHz! It works fine with 8MHz internal oscillator :)


  • Hardware Contributor

    @carmelo42 Sorry for a late reply. In short C2 is to reset the avr, C1 and C3 are to decouple the avr. And C4,C5 for the radio as you say. The caps are there as a recommendation, precaution, stability, etc, and all of them are not always necessary when it's supplied by battery.
    And yes, the idea of the FTDI-6-pin-header and bootloader is to provide ability to load sketches the normal Auduino way with FTDI and Arduino IDE.



  • This post is deleted!


  • Hello, I have built a number of these sensor nodes and really like the generic design!
    However I have run into trouble when trying to build a power meter with a photo sensor.
    I am using the code from MySensors but also tried other sources but my problem is that the digital pin i am using (D3) dont drop enough for the sensor to treat it as digital 0 as it stays at 2.3 V with a 2 AA battery power attached

    When trying the pulse sensor with external power it works perfect so it seems like D3 is floating which also is confirmed when I measure on D3 without the sensor attached. (approx 2.7V)
    I have used this row in my sketch pinMode(DIGITAL_INPUT_SENSOR,INPUT_PULLUP);

    Any clues what I can try?


  • Hardware Contributor

    @miljume said in ๐Ÿ’ฌ My Slim 2AA Battery Node:

    INPUT_PULLUP

    What kind of sensor do you use? Some sensors have an analog and digital output. The Digital should return either 0V or VCC while the analog returns all analog values between 0V and VCC.

    You could try an external pulldown resistor of 10k to ground if you think the pin is floating.

    Another approach is to elaborate with a photoresistor only and to get a clean 0/1 use an transistor. If the voltage drops to low though for the pin to get a clear 1 (2.4v on 3.3v atmega) you might need a DC/DC step up booster.



  • @sundberg84 Thank you for your feedback! I used the design found here so the sensor is OK. I had also tried to use a pulldown resistor but it showed that I had used too low value. When I use 10k as you suggested it worked like a charm, thank you! What I dont understand is why I should need the pulldown resistor in the first place? Shouldn't it be possible to solve that in the software?


  • Hardware Contributor

    @miljume - I dont think you can solve a floating pin in the software. Im not that experienced with internal pullups either so someone else have to answer that. Good you have it working though!


  • Contest Winner

    Internal pull-up resistors have 20-50k resistance. It may be not enough.



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