Badges come in all shapes and sizes, but a badge that draws on a stack of Post-It notes is definitely a new one. The design uses three of the smallest, cheapest hobby servos reasonably available and has a drawing quality that creator [Bart Dring] describes as “adorably wiggly”. It all started when he decided that the CNC and mechanical design world needed to be better represented in the grassroots demo scene that is the badge world, and a small drawing machine that could be cheaply made from readily available components seemed just the ticket.
Two arms control the position of a pen, and a third motor lifts the assembly in order to raise or lower the pen to the drawing surface. Gravity does most of the work for pen pressure, so the badge needs to be hanging on a lanyard or on a tabletop in order to work. An ESP32 using [Bart]’s own port of Grbl does the work of motion control, and a small stack of Post-It notes serves as a writing surface. Without the 3D printed parts, [Bart] says the bill of materials clocks in somewhere under $12.
We’ve seen similar designs doing things like writing out the time with a UV LED, but a compact DrawBot on a badge is definitely a new twist and the fact that it creates a physical drawing that can be peeled off the stack also sets it apart from others in the badgelife scene.
For many projects that require control of air pressure, the usual option is to hook up a pump, maybe with a motor controller to turn it on and off, and work with that. If one’s requirements can’t be filled by that level of equipment and control, then it’s time to look at commercial regulators. [Craig Watson] did exactly that, but found the results as disappointing as they were expensive. He found that commercial offerings — especially at low pressures — tended to leak air, occasionally reported incorrect pressures, and in general just weren’t very precise. Out of a sense of necessity he set out to design his own 
