• Energy Harvesting Module

    Alexandre LE GALL7 hours ago 0 comments

    Here is a 3D model (kicad 3D view) of the Energy harvesting module.

    It is based on a BQ25504 Energy Harvester (with MPPT and Battery management), pair with TPS63030 Buck/Boost Converter. It's perfboard/breadboard compatible.

    There is also a 1V precision voltage reference.

    You can adjust the parameters (Under & Over voltage protection, Output voltage...) by changing the value of some resistors.

    I also made a breakout board for BCAP0350 E270 T13 Supercap (350F, 2,7V).
    It's also perfboard/breadboard compatible, but you can use M3 Mounting Hole as terminals if you want (for high current).

    There will be more details (explanation and schematic) on the main project page.
    I still have to do the other modules (I2C motor driver, sensors...) before I can order PCBs and components (and wait for my salary).
    I also have to open a GitHub repository to share files and documentation, but I have never used it ...

  • Somes calculations = autonomy of +60 minutes

    Alexandre LE GALL03/27/2018 at 11:09 0 comments

    I juste made some simples calcultation to find out if it's possible to power the robot with potatoes energy.

    The energy is harvested from a single potato in two super capacitor (2.7V / 350F).

    If i place the two capacitor in series, it gives me a single capacitor of 5.4V / 175F.

    The energy inside capacitor is :Energy in Capacitor

    I don't want overcharge it, so i will charge at maximum 5V :

    To extract maximum energy from capacitor, i need a boost converter. Because of the energy harvesting IC, i can't discharge over 2.2V :

    I can store and use 2187.5 - 423.5 = 1764 J (0.49 Wh)

    At 3.3V, my two motors use each 25mA (light load). (3.3V * 25mA = 82.5 mW)
    The electronics (µC, sensors... ) sould use maximum 50mA. (3.3V * 50mA = 165mW)
    In total, i need 0.33W. (2 * 82.5mW + 165mW = 330mW)

    With 75% efficency boost converter, i should use 0.44W of power from the capacitor.
    With a consumption of 0.44W and a capacity of 0.49 Wh, i can power the robot for 1.11 hours (66 minutes, 49 seconds)

    If i want know how long i can charge my capacitor with potatoes, i have to measure how much power i can exctract from it...

    Edit after some datasheets reading and power consumption measurement of my new tiny motor...