Please read part 1 for context. If you don’t want to, here’s a quick summary:
- Many bike counters are induction loops
- they work by looking for bike-like signatures in change of inductance over time
- I want to make non-bikes get counted as bikes
- they work by looking for bike-like signatures in change of inductance over time
Thanks to Neil on Facebook Marketplace who gave me a bike for free (he said on the listing that it was likely just useful for spare parts). It was quite useful!
Before I disassembled it, I took it over to the counter to do some more testing. I found that the orientation of the wheels doesn’t seem to matter much, but what does matter a lot is the distance between the wheel and the loop. I didn’t measure precisely but it seemed to be that if I held the bike anything more than ~2 inches above the ground it wouldn’t get counted. As I alluded to in Part 1, the coupling between the wheel and the loop falls off very quickly with distance. I also found that you can’t be going too slowly (there’s likely a cutoff for the time window the counter looks at to evaluate a signature).
Most importantly, I figured out that this particular single loop system doesn’t seem to care which direction a ‘disturbance’ is coming from (maybe you’d need multiple sensing zones or a classifier specifically for distinguishing reversed signatures).
Meaning, if I push one wheel over the loop, and then drag it backwards within a reasonable time frame, the signature is treated as more or less the same and it counts as a bike. This makes total sense and I probably should have realized it before. I also confirmed after removing the wheel from the frame that it is in fact the part of the bike that produces the important parts of the signature.
These findings make it easier to create some type of object that gets counted as a bike, since we can space things out temporally instead of physically. The only challenge is that it needs to go over the loop and back in a somewhat natural way.
The first thing that came to mind was the ‘swinging’ motion that happens when carrying a bag. I present: THE BIKE BASKET
In summary: I put a bike wheel in a basket, innocuously covered it with a shower curtain, and when you swing it over the loop it gets counted as a bike.
It’ll be hard to match the smoothness on display in that video in the next iteration, but all in all I’m pretty happy with this for a first attempt.