Our Solar Experiment: Testing, Testing, and More Testing

As mentioned earlier, our second launch is going to have a few differences, including a bigger balloon, a redundant tracking system (APRS), and a different Lego minifigure.

However, the biggest difference is this time, we are going to conduct a solar experiment on board the Loki Lego Launcher.  We are using a solar panel from a solar experiment kit, and we are beta testing a voltage/current sensor from High Altitude Science.

Here is our hypothesis:  as our spacecraft rises higher through the atmosphere, the output produced by the solar panel will increase, as there are fewer particles that will block the sun.  To test this, we will measure the output of the solar panel on the ground by using the voltage/current sensor, and then, when we launch the Loki Lego Launcher 2.0, the flight computer will continue to track the output as it rises.  If our hypothesis is correct, when we analyze our data, we will see that the current increases the higher the spacecraft goes.

Our sensor is also wired to measure the computer’s current consumption. We will have to subtract the amount of current that our computer uses from our total amount of current to get the amount of current that our solar panel absorbed.

On Sunday, we tried to figure out how to wire our solar panel to the voltage/current sensor, and how to position it on our spacecraft.  We tried many different configurations and did test after test after test.  We think we did at least nine different tests that day, trying to figure out the best way to measure an increase in output of the solar panel.  We were doing all the circuitry and wiring ourselves from scratch, which is tricky since we’ve only done some basic stuff at school.

At first we thought we should connect our circuit in parallel, but we wanted to measure voltage, so we connected it in series. But the way the wiring works, connecting in series means that we would need to have the solar panel in complete sunlight for the circuit to be completed and for the entire flight computer to work at all. It wouldn’t track any data. We thought we could use a jumper cable to override the circuit, and it did. A little bit too well.

Current will always follow the path of least resistance and it completely bypassed the solar panel, not getting any energy from it at all. After we figured that out, we went back to connecting the circuit in parallel and measuring current instead of voltage. That way the whole computer would still work without the solar energy, and we could still continue our experiment.

When we tested this configuration and then checked our data, we saw that the current and power increased when we put the solar panels in sunlight, and then decreased when it was in the shade.  Yay, finally!

test data
The highlighted numbers show when we put the solar panel into the sun and the amount of current increased.  Data!

We’ll keep you updated on information. Stay tuned!

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