WSN node power supply

Discussion in 'General Electronics Chat' started by alexx_88, Jun 7, 2011.

  1. alexx_88

    Thread Starter New Member

    May 24, 2010
    17
    0
    Hello,

    I am working on building a solar panel supply for a WSN node.

    The logic of my design is the following:
    - the Attiny uC is powered by a battery and monitors the voltage on the supercap. Whenever it decides that the supercap holds enough energy, it turns the TS5A3166 switch on and the node is powered. I have built the board and I am having some unexpected results even from the first tests.

    The solar panel is rated at 6V and 100mA. The supercap is balanced with 2 * 10k resistors, values which I have calculated from the producer's recommendations.

    I am currently testing with a 9V battery connected in series with a 150 ohms resistor and then fed on the board using the "SOLAR" connector.

    Basically, I am seeing two problems:
    1) The zener diode doesn't limit the voltage. It goes up to 4.6V without the supercap connected.
    2) The LED on the "SW_OUT" line lights up whenever I put the power on, with the "IN" control pin of the TS5A3166 in a high impedance state. I have checked the connections on the TS5A3166 with a multimeter and they seem ok.

    I would highly appreciate any comments regarding these questions and the design itself.

    Thanks,
    Alex
     
  2. alexx_88

    Thread Starter New Member

    May 24, 2010
    17
    0
    Okay, so the problem with the led was pretty simple actually. The control pin "IN" of the switch was in a high impedance state. As soon as I connected it to GND the LED stopped. So that's one problem gone.

    The one with the zener diode still remains though. :(

    Alex
     
  3. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    Well, I would think that either the zener is a dud, or it's not connected as shown. It can't be hard to tell which. A continuity test would be a first step, and if that shows it connected correctly, try replacing the diode. Could you have fitted a plain diode by mistake?
     
  4. alexx_88

    Thread Starter New Member

    May 24, 2010
    17
    0
    Ok, thanks for your help. The problem was not with the diode (broken or anything) but the model I picked. this. It has a zener current rating of only 5mA, while my test rig generated quite a bit more.

    I will buy a proper zener diode and hopefully everything will be ok.

    Thanks again,
    Alex
     
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