Hi everyone, I have just signed up after seeing odrive on Thomas Sanladerer’s YouTube video and found a few similarities with something I’ve been working on.
My idea is a scara arm milling machine. I know it’s never going to be as rigid as a Bridgeport but that wasn’t my biggest problem, it is eliminating backlash.
Very low backlash gearboxes are very expensive so I could either use a very large ratio single stage reduction with huge wheels which would restrict access and visibility or use a servo motor with the encoder on the final gear.
As I couldn’t find any very high resolution encoders I was working on the big single stage idea with the large worm gears under the table (and having to hob the gears myself). Then I started thinking about any consumer products I could use as an encoder and came up with tape recorders. If I could use a magnetic tape and tape head as an encoder which led me to CD’s.
My idea is to write a CD with a continuous track of 10101… and read with a standard cd head.
CD’s use complex encoding but without this you could get resolution of 2.25 million per revolution using either rising or falling edges or 4.5 million using both on the outside edge of the disc.
CD’s are written in a spiral but this would not matter for my application as I only need half a revolution. And even if you used 1000 revolutions the you would only be out by 0.0027%.
There will obviously be a bit of work getting a microcontroller to read from the CD head and control the tracking as well as how to write the cd in the first place but I think that’d doable.
A single one bit track will only give distance not direction or absolute position but fourbbit grey code would possibly work to give direction once two full codes are read.
Anyway it’s just in my head at the moment so if anyone has any ideas or wants to try it out I’d welcome your input.