OurWeather – Solar Power Extender Kit First Tests

We are now running the first system tests of our Solar Power Extender Kit for the OurWeather no soldering STEM Weather Kit.   The kit contains a SunAirPlus solar controller and data collector board and a 330 mA / 6V solar panel (and maybe two panels depending on the tests).

What is OurWeather?

OurWeather is an ESP8266 based  connected weather station containing 7 different sensors that will teach about electronics, software and the weather.   It contains all the sensors and wires to make a fully functional, WiFi weather station.   No software programming is required, it works right out of the box. However, if you want to change the way OurWeather works, add your own software or do something entirely different, we have the Open Source software available.   And what is one of the coolest features of OurWeather?   Building the kit requires NO SOLDERING. It uses Grove Connectors.    It is all plug and play based building, with a full step-by-step photograph based instruction manual.  It is a safe and educational way to learn about weather, electronics and science topics.   You can watch our successful kickstarter video here: https://youtu.be/pw6hSNSQnsM

See the Grove Connector Tutorial Here.

Initial Results

We have been running it for a couple of days gathering data (SunAirPlus reads the currents and voltages of the whole solar power system (solar panels, battery and load – OurWeather) and reports it to OurWeather.   We use our DataLogger software to gather the data from OurWeather (over the WiFi using the OurWeather REST interface) and create the graphs below.   The graph below shows the first full two days out in the Sun.   We started with a partially discharged battery because we needed to see the On/Off behavior when the system hits a brownout (meaning the battery hasn’t been getting enough power to keep running) and how it wakes up.   Based on the way it wakes up, it works but we need more data to determine if we need to add a USB PowerControl into the package to add more hysteresis.   The hardest question on a solar power system is to make sure the unit comes up in an acceptable way after running out of power.

The middle of the graph shows a full day of sun (ignore the times on the graph – they are in UTC and we are running the test in Pacific (PST) as in the title). It shows that SunAirPlus and the solar panel is doing a good job charging the battery for the first few hours.  The up and down of the currents are from clouds moving over the sun.  It eventually turns complete cloudy and started raining.  We know that the system is going to run out of power (that is what we are testing for) and you can see the current go up from the battery until the SunAirPlus turns the power off (you don’t want to deeply discharge LiPo batteries).   It then wakes up the next day.   Note that SunAirPlus is saying that OurWeather is using about 70 mA of current.  Since SunAirPlus is reading values when the WiFi is enabled, it reads high.  We need to stick in a moving average for current to get a better overall average.  We are thinking it is actually about 40mA.   We can reduce it further by unplugging the OLED display but we want to visually see what the system is doing during testing.

 

In the graph below, you can see the battery start to run out of power and then SunAirPlus shuts OurWeather off.

 

Conclusion

We are going to run these tests for about a week and look at all the data.   Right now, we are thinking we will may add the USB PowerControl to the kit to improve the on and off behavior of the unit.   Before we decide how many solar panels to supply, we will unplug the OLED display for OurWeather and rerun the test.