John McNelly's Raspberry Pi Pico-Powered Drill Periscope Ensures Perfect PCB Holes, Every Time

John McNelly, electrical engineer and self-described "tinkerer and breaker of things," has made the process of drilling accurate holes in homemade PCBs — or anything else — as easy as it can be, by upgrading a drill press to include a digital periscope with cross-hair targeting.

"In the course of home-etching a bunch of PCBs, I've spent many hours hunched over my drill press squinting at tiny drill bits and trying to line them up with pads for vias and through holes," McNelly explains. "These pads can be quite small: the smallest rivets I use have a pad size/head diameter of just 0.9mm, and a drill bit size of 0.4mm. After doing this for a few years, I came to the conclusion that there must be a more ergonomic and accurate solution to this problem."

Having tried using CNC milling before, but looking for a better solution for quick one-off jobs, McNelly turned to the idea of creating what is, effectively, a bomb site — a digital display which pops a cross-hair exactly where the drill bit will impact, which when added to a manual drill press means perfectly-centered holes every time.

"I had a few other design features that I wanted in my own drill press camera system," McNelly writes of his reasons for designing his own solution, rather than following in someone else's footsteps. "No external PC required (stand-alone microscope, ideally with its own screen). Removable/no permanent modifications to my drill press (I often use it for woodworking and metalworking in addition to PCB drilling). HDMI output to drive an external display for a more detailed view. Easily adaptable to fit multiple types of microscope cameras."

In order to fulfill those requirements, McNelly eschewed the traditional approach of mounting the camera directly beneath the drill bit in favor of a mirrored periscope arrangement. "The microscope camera would lay horizontally on top of the drill table," the maker explains, "and a 45 degree mirror in front of the microscope camera would provide a view of the underside of the PCB. Even better, with this design topology, I could use my old Andonstar ADSM201 HDMI microscope camera, and the screen would rest at a convenient viewing angle for me to look at while running the press!"

With addressable RGBW LEDs as a light source, the entire unit is driven from a custom PCB — drilled on the very same press — hosting a buck converter, color and brightness controls, and a Raspberry Pi Pico running MicroPython. A 3D-printed chassis holds everything together, while strong magnets attach it to the drill press — and the cross-hairs are, simply enough, drawn over the display using a removable marker and a steady hand.

McNelly's full write-up is available on his blog, while the project's source code, CAD files, and Gerber files have been published to GitHub under an unspecified open source license.