Battery based atmega328p sensor (no SMD)




  • Hardware Contributor

    Just added some info to test the forum connection.

    Board is fixed, BOM is fixed. Instructions need to be elaborated more.


  • Hardware Contributor

    Added a reply to see the result.



  • It seems that the BOM is empty.


  • Hardware Contributor

    As mentioned, work in progress ...


  • Hardware Contributor

    BOM added


  • Hardware Contributor

    Added some pictures and text.



  • This is a perfect node. I have a few of these with different sensors and also got a few 3D printed cases for 2xAA PCB fit


  • Hardware Contributor

    @alexsh1

    Do you use both NRF headers on different nodes, or always the same header ? I plan on improving this node, and I think only 1 NRF connection header is needed (my preference is in the same axis as the atmega328, like in the picture).

    What is your opinion on the two NRF headers ?



  • @GertSanders

    I am using both NRF headers depending on the I2C module I am using. Somethings the tip of nrf24l01+ is not going well with a wider sensor.
    Having said that this is not a problem and one connector can go.

    Another problem I am facing is that SDL and SDA on all sensors are differently placed. I wonder if this is possible to swap with a jumper?
    What's your view?


  • Hardware Contributor

    @alexsh1 In my AC board I have added jumpers to swap the position of the SDA and SCL pins. I plan to add those jumpers to a new version of this battery based node. It will give more flexibility.

    I also sometimes use a wider Temperature/Humidity sensor board (HTU21D) instead of the SI7021 boards with GY-21 marking. The I2C pins are swapped, and the width is indeed different.

    I have also reconsidered how to connect the other pins, so I'm thinking of using angled JST connectors (like the power connector for instance).

    Using only 1 header for the radio will allow more clearance between the I2C pins and the rest of the connectors.

    I'm also quite happy with the "smd" version of the NRF24L01+ boards. Very small and yet works about the same range. This removes the need for the big 2x4 header completely. I used it on my very narrow board.



  • @GertSanders I had to use Dremel to trim down HTU21 board (I posted photos on the forum). There are no components so I do not understand why they have a wider board.
    JST connector is useless in my case as I am powering all nodes from batteries or FTDI. Potentially, you may remove it too.
    In relation to SMD nrf24l01+ I think it is brilliant. I have been using one with your narrow board and another one with sensebender. They really save a lot of safe for the header and the board itself. Alternatively, you may be designing the board with a built-in nrf24l01+., but it would require some SMD soldering.


  • Hardware Contributor

    @alexsh1 said:

    nrf24l01+

    Soldering a nrf24l01+ is beyond my capacity for the moment, I do not plan to do that. But the modules with 1.27mm pins (the "smd" variant) are feasable.

    Someone already made a board with built in nrf24l01+ and PCB antenna:
    https://www.openhardware.io/view/31/MySensors-Stable-Node

    I'm now going to make a variant of the narrow board for the LNA+PA smd version. These boards also use the same 1.27mm spacing and castelated pins, but the pin connection is different, so not compatible with the smaller non PA+LNA smd boards.

    I have seen small nrf24l01+ smd boards with the same pinout as the larger PA+LNA smd nrf24l01+ boards. So maybe we should "standardise" on that pinout.

    Small smd version pinout (the one I use):

    VCC (1.9 - 3.6V)
    GND
    CE
    CSN
    SCK
    MOSI
    MISO
    IRQ

    Larger PA+LNA smd version:

    VCC (2.2 - 3.6V)
    CE
    CSN
    SCK
    MOSI
    MISO
    IRQ
    GND



  • @GertSanders Yeah, I understand - this is a very small chip.

    I looked at this board with built-in nrf24l01+ but my SMD skills would not allow me to do it. I may get away with a few components, but not with the whole board. I am looking at a few soldering/rework stations right now to allow me to do SMD, but currently I do not have tools needless to say about skills.

    With regards to nrf24l01+ SMD, I purchased a pack of 6 from Aliexpress and they have the following pin-out:
    VCC
    GND
    CE
    CSN
    SCK
    MOSI
    MISO
    IRQ

    These are the same boards you used as well (or similar in terms of pin outs) and I suggest to stick to that. LNA+PA SMD is a special one - how many would really need it? I have LNA-PA installed on my GW and can install one one the node if I have to, but out of all my nodes I only have normal and SMD ones.



  • @GertSanders The other point is that your node is small and compact enough (my limitation was the 2xAA case in terms of length and width). Is it really necessary to go fully into the SMD?


  • Hardware Contributor

    @alexsh1 . No, I do not plan for this board to be full smd. The smd version of the atmega328 is also wider then the DIP version. So for very narrow boards, it would not make sense to use the AU variant of the cpu. The narrow board will stay a DIP based - mostly throughhole board. So will this board.

    I am tempted to try a version with 0805 size smd resistors, which are still soldarable by hand, and yet much smaller then 1/4W (7mm) resistors I use now. But again, no real use case right now.



  • @GertSanders

    This is what I mean in terms of size...
    0_1456923449282_2016-03-02 12.19.51.jpg


  • Hardware Contributor

    @alexsh1 Nice box :-)

    Related to size: I plan to keep the board size within 50 x 24mm so that I can get 2 nodes out of a 50x50mm board. It also corresponds exactly to the size of a 2xAAA battery holder, which is a little smaller then the 2xAA battery holder you use.

    Here is the preview of where I am at now. This still needs to be routed, but for the moment I'm looking at placing components in the most efficient way (and trying to imagine how I would route wires around this node in tight spaces.

    I'm also planning to include ATSHA204 and flash to make it a full MySensors compatible node (minus the MYSX connector, not sure what to do with that yet).

    0_1456935537305_V3 layout.jpg

    The working file schematic is still in "movement":+1:

    0_1456936199626_Schema v3.jpg



  • Just a quick hello to say your Battery based atmega328p sensor (no SMD) and the companion boards are exactly what I was looking for. Ordered 10 of each today and cant wait to get cracking on building them.
    Great work btw



  • @GertSanders you decided to keep JST I see. A few more jumpers here :)
    Also do you assume soldering ntf24l01+ directly onto the board or via pins?



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