Brass initials triggering LEDs

This project, brass initials for my buddy’s kids, was executed entirely at Ace Monster Toys. The brass initials hold a little magnet that triggers a reed switch to light a few LEDs. The brass was machined using AMT’s CNC milling machine with CAM G code generated by SolidWorks (and I’m getting up to speed on the free alternative Fusion360). I broke a few 1/8″ end mills before converging on the right settings: 0.1″ depth of cut, 2500 rpm, and a 3 IPM feed. Dry machining with forced air worked well and was compatible with the way I mounted the brass sheet, which was superglued to an aluminum block. I polished the brass with needle files, sandpaper, and a polishing compound as guided by the fantastic Clickspring videos on Youtube, then dipped the pieces in thinned lacquer.

The base is an acrylic disc that I roughed up with large-grit sandpaper to more evenly diffuse the LED light. Next to the reed switch is a little steel block that gives the magnet something to snap on to. The reed switch switches from a couple CR2032 coin batteries charging two 1.8 mF capacitors to dumping their energy into the LEDs through a 100-ohm resistor. The component are messily hot-glued into place (the step I’m least satisfied with), and there’s a thin back piece that screws on with 1-72 brass screws, which let me practice countersinking.

I only put these in the mail yesterday, so the reaction of the recipients is, as yet, unknown.

16 MB .mov file of operation

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