--- In
Homebrew_PCBs@yahoogroups.com, "designer_craig" <cs6061@...> wrote:
>
> Tell me more aobut you photo plotter. I always wanted to build one but never had the time. What did you use for the drum? How are you doing the pixel timing as the drum rotates? Are you using a rotary encoder or just timing from an index pulse. What RPM are you running?
Just to give a little more specific answers to your questions:
I made the drum out of Plexiglas as I had planned to make it a transparency scanner as well as a plotter. I no longer need to make a scanner myself, so I never built that option.
I made a mandrel out of an old tree trunk, and wrapped the Plexi around it after heating in the home oven. I made two end plates, with screws drilled and tapped into the ends of the Plexi. I then turned it to diameter, making a finish pass at work where they have more accurate lathes.
Yes, a shaft encoder with 1024 lines/rev plus index. No way would a single index pulse be accurate enough.
600 RPM, but actually with the PRD film, I very likely could go to 1200 RPM if I can get the film to stay on the drum. This PRD is significantly more sensitive than the HTR3. I tape it on with black electrical tape to the drum.
Jon