I recently visited the Henry Viscardi School, showed them some of my past AT projects, and asked them if there’s anything I could help them with. One thing they came up with was an AT device to allow students to draw on actual paper using a joystick. There are many ways to achieve this, but for this first round of prototypes I went with some rotary servos for the arm and a linear servo for the hand.
Here’s a version I thought would be really fun, painting with watercolors:
Here’s the same mechanism drawing with a pen. I reversed the spring position inside the pen so that it is always pushing out with the right amount of pressure against the paper to leave a mark.
Here’s the same mechanism drawing with a marker but with a few changes. The control mechanism demonstrated is a set of switches (with a short press of the down switch toggling the marker height, and a longer press moving the arm like the other switches). Since the marker doesn’t have an internal spring I added an external one to control the pressure of the marker tip against the paper. I didn’t get this exactly right in this version so it draws a little rough, but you can see the basic idea working. Also decided at this point there was enough potential to take the time and solder up a board with both the joystick controls and switch jacks for switch access.
Please note that with this system you can use any of these control methods for any of these drawing methods.
Here are some pictures of different attachments on the arm for the first iteration. The next version will have a clamp that could hold an drawing/painting tool without modification.
I’ve uploaded the code I wrote here: https://github.com/bobparadiso/rotaryServoPainter