Blind as a Bat
Now that the lifting mechanism is up and running relatively trouble-free, it was time to get some feedback from it. I wanted to be able to see how high the model is at any given time.
My first attempt was using an ultrasonic sensor which basically sends out waves and calculates its distance away from something based on how much time it takes for the wave to bounce back. I’ve used this sensor before in a collision-avoidance robot which was fairly reliable so I thought I could use it here too.
Unfortunately, it didn’t work out how I expected. The delays within the code to make the sensor work interfered with the stepper’s performance. The values from the sensor would also randomly give strange values, though that might have been the fault of my shifty setup.
I eventually decided to try another sensor…
The Magnet Kabob
A hall effect sensor can detect magnetic fields so, while the resolution wouldn’t be as accurate as what I hoped the ultrasonic sensor would have given me, I thought as long as I could track key heights of the model (like when it’s at the top or half-way down), I would be good.
I manually moved the model to various heights and attached magnets at these points where the hall effect sensor would pick them up. I started calling it a magnet kabob…
Although it was working how I expected, it wasn’t ideal. After receiving some pointers on Twitter, I threw out this setup too and tried something else which you’ll see in the next update.