My latest robotics platform is the DFRobot 4WD, a respectable step up from the Tamiya Tracked Chassis I was using before.. The second thing I bought after the platform itself was the standard Wheel Encoder Set that everyone probably buys when they get the chassis. This has proven to be a pretty valuable lesson in what to look for in encoders.
Installing them was pretty easy and didn’t pose any serious problems. On my pair the spacers that set them away from the gearbox were too short and so I trimmed down some spacers I already had. My real problems started when I tried using them… Basically, I don’t think they’re good for anything but very rudimentary feedback. They simply don’t have the resolution I would like, especially at lower speeds.
To squeeze more resolution out of them I made some encoder wheels with 16 divisions instead of 10. I used the program mentioned in this article and had Kinkos print them onto some transparencies for about $1.50. I tried a few different resolutions, including some very optimistic ones and 16 was the best. You can see that I doubled up two copies as that felt stronger and was sure to block out any imperfections each wheel had from the printing. Right now I’m happy enough as I’m using fast enough speeds so that I get enough ticks per cycle to produce feedback on. I’ve been considering ways to move the wheel to the motor shaft itself, before the gear reduction where it’ll be moving much more (maybe too much!), especially at lower speeds. Not sure it’s possible yet, as that will be a very tight fit. Anyway, though it may go without saying, don’t expect the world from these encoders and if you’re already considering a more serious solution you may just want to skip to that.