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

 

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

 

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?

 

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