Garden solar light + Booster + ESP32 + Moisture Sensor Likely to work?



  • Hi,

    Probably being over-optimistic as usual but...

    Is it feasible to create a system with the following items:
    Solar Garden Lights: Example
    DC Booster ie http://www.ebay.es/itm/112468163238
    or https://es.aliexpress.com/item/0-7-5V-to-3V-3-3V-5V-DC-DC-Boost-Converter-voltage-Step-up-Module/32800430445.html
    ESP32 or ESP8266
    Moisture Sensor

    that at night takes a reading from a moisture sensor and sends it via wifi to a control.

    I guess that the battery would have to be able to keep enough power for 24hr of sleep mode for the ESP and then for the sending of data once a day.

    Later I plan to swap the battery for a supercapacitor and create some sort of irrigation system but for now I just want to know if the battery from a small solar light will work through a booster in this way?

    Thanks,
    xgarb



  • I thought I'd turn folks on to a find at my local Wally World...
    They are selling their house brand solar LED garden lights for discount, and I picked up 4 of these for $0.97 each.
    They are each for 1.2v (LED & 150mAh NiCad), but I was thinking 3x at 3.6v for a Pro-Mini, so I grabbed a few. I created a photo album of total disassembly here, and here is one of those pics:

    alt text

    Of small note is that the NiCad battery itself is more than $1 each! I'm still thinking about how to combine them to power a Pro-Mini, but for less than the price of the battery you get a nice case, an LED, and a solar panel! :)


  • Mod

    My plan is to use 2x nimh batteries. Nimh can need up to about 1.5V before they are fully charged (depends on how fast the solar panel can charge them but for a small panel charging will probably be less than 0.1 so 1.45V should be enough to fully charge)
    These lights usually charge directly from the solar panen to avoid having to add a charging circuit, to keep cost and complexity down.
    3x1.45V=4.35V which is more than most 3.3V components can handle.

    The atmega328 works down to 1.8 with lowest BOD. Rfm69 works down to 1.8. Nrf24 works down to 1.9.

    At 1V a nimh is almost totally exhausted. So 2x nimh gives enough voltage at the low end for the components I usually use. This avoids adding a step up/down which means lower complexity and cost, and no loss of efficiency due to conversion.

    These are just my thoughts so far. Hopefully improvements can be made :)


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