BigWheel In-Line Switch

thingiverse

The BigWheel in-line switch is designed for low voltage DC applications only. DO NOT use this as a high voltage AC switch. If you burn your house down, don't say you weren't warned. Unlike most of the designs on Thingiverse (some of them my own), this is not a housing or enclosure for a manufactured switch, but a home brew switch from the ground up, The principle is pretty basic: a rotating wheel with a conductive strip attached to it bridges the gap created in the positive wire of the circuit. This uses 24 gauge speaker wire and a snippet of aluminum from a beverage can. Cut a strip of aluminum 8.5mm x 18.5mm. Be sure to scrape off the thin layer of epoxy that coats the inside of the can; it's an insulator and the switch won't work unless you're down to bare metal.. Wrap the aluminum around a small cylinder (8mm ±) in order to create a curve to make it easier to feed into the slots in the wheel. As for the wire, snip the positive wire only and strip about 5 or 6mm of insulation on both sides of the cut. Twist the ends neatly and tin them with solder. Now remove a a small amount off each side of the cut to create a small but definite gap in that conductor. Set the wire into the channel in the housing with the cut wire facing up and so that the gap is in the middle. Insert the the bare aluminum strip into the slots in the wheel. It's OK if it bulges a little. Once properly installed into the switch body, it will be fully contained and have no place to go but in the circular path created for it. To install, tilt the aluminum strip against the snipped ends of the wire, and seat the wheel on the center axle. Now install the other half of the switch body and tap it together. Finally hook up the two ends to a power supply and load. I've built a few of these and they've worked pretty well except for the time I forgot to scrape the coating off the aluminum. BTW, calling this thing "big" was a bit of an exaggeration. It measures 32mm long, 17mm high (22mm including the wheel) and 15mm wide. Fusion 360 files are included if you wish to modify this design.