Too many people view old, obsolete electronics as little more than scrap - but to the maker a pile of outdated gadgets can be a treasure-trove of cheap components. Earlier this month, Nerd Club's Chris Holden detailed a homebrew CNC pick-and-place machine built using stepper motors and other components from a flatbed scanner and a DVD drive. Designed to speed up the process of placing surface-mount components on a circuit board ready for soldering - although the result, Chris admits, is a device which actually takes longer than doing the task by hand - the build is interesting for several reasons, but the publication yesterday of a schematic and PCB layout for the controller make the project a great way to learn about creating low-cost CNC platforms suitable for everything from pick-and-place to milling. Chris's explanation of the way the data is communicated while allowing the motors to continue to operate is also a great way to learn about the details of computer-to-microcontroller communications ahead of building your own projects.
Even though it is highly accurate (to within 0.05mm) the flatbed scanner bed is running a little slow, even when the motor is spinning as quickly as possible (we have to have a 2ms delay between steps, otherwise the motor locks up). So while, in principle, we're calling this a success (it can populate a pcb automatically from a list of co-ordinates) in practice it's actually quicker to place a dozen or so components by hand, using tweezers!