Solar monitoring back online

The solar instrumentation has been lacking for a couple of months since the solar panels’ current sensor blew up. It took 2 months because there has been a lot mistakes and learning along the way. It should have been simple, replace the 30A sensor by a 100A one right?

Well it wasn’t. First I ordered the wrong 100A sensor, meant for AC use. Then I had a myriad of issues around calibration.

  • at the 5V input port, a 0V reading didn’t translate to 0A, this sensor goes from -100A to 100A so it is 2.5V which translate to 0A.
  • with the skew from miscalibration, the value I was getting made no sense for what I know the panels can make
  • orientation matters as again, this sensor can read negative values
  • a cloudy day makes fluctuations hard to detect
  • moving the sensor from one interface kit to another after calibration resulted in another skew.

All these little things I could have picked on their own, but together they conspired to make me thoroughly confused and left me seeking support from the Phidgets forums. I was once more impressed by Phidgets, the help I got was fast and efficient. Phidgets are more expensive but I was proven once more that they are worth every penny. They have many other advantages, I have nothing but good things to say about them.

Calibration, I really need to tidy things up in there

I’ve learned a LOT of lessons with this one. Not the least of which is to be ok with the imperfections of analog data. I’m a discrete data type of guy, it doesn’t come naturally to accept skews & variations.

More solar lessons

I always wondered why the solar array never produced more than 30A, especially after I added 3 more panels to it. Well, I got my answer yesterday when the array took an unexpected dive.


I had forgotten that the amperage sensors I got back in 2015 are only rated for 30 Amps, way overkill at the time :). So it’s entirely possible the array was producing more and I simply wasn’t able to “see” it. Also, the extra panels pushed the sensor over the edge and fried it.

I put in the order for new sensors rated for 100A, it will be interesting to see what the graphs look like. Their design also makes it so if they fail, the production won’t be impacted because they aren’t part of the circuit.

It’s surprisingly difficult to find such sensors rated for high amperage. Phidgets are expensive but they pretty much have the only industrial IOT sensors. In my experience they are robust and easy to deploy thanks to great documentation & code samples.


Another Winter another solar upgrade. Short overcast days are good at exposing a lower limit. After having lost power a couple of days it was time for an upgrade. The house is growing and so it our consumption, especially on the Summer months when we get used to abundant electricity.

Bringing the panels on site, I always said my son would make a great draft horse.

I’m becoming good at building in the cold, my fingers are not thanking me though.

All I need to do now is prop it off the ground and anchor it for heavy winds.


I like this frame, it takes 6 2x4x8 and this is the only scrap lumber left.

I did some quick back of the envelope math and so far our setup costed about as much as what we would have paid for grid electricity these past 2 and a half years. Seems like it costs about as much to learn how to fish than it does to buy fish, at least at the beginning. We have now entered the gravy zone.