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Motorized Butterfly Capacitor Works

Here is a narrated video of the motorized butterfly capacitor in action.

For around $35 in materials (plus an Arduino) you can build a motorized butterfly capacitor for a magnetic loop antenna. The system shown here is a prototype, but it is probably close enough for prime time.

  • The capacitor plates were milled from aluminum sheet using my CNC. It is possible to cut your plates by hand from thin aluminum or even copper printed circuit board material. Or, you can buy professionally made capacitor plates from a number of sources, including VA6POP here in Calgary.
  • The plastic parts were all home printed. There are lots of models on Thingiverse for making bolts, nuts, washers, couplings and gears. Many of these are configurable, which means you can adjust the dimensions as you wish.
  • The hardware is commonly found in big box or specialty hardware stores.
  • The electronics and stepper motor are cheap on EBay.

Eventually, this motorized butterfly capacitor system will be mounted on a section of one inch PVC, which will be the base for my magnetic loop antenna. Weatherproofing will be achieved by mounting the sections in cheap plastic food containers from Walmart. I have some left over plastic tubing to protect the threaded rod between the capacitor and motor assemblies.

Motorized Butterfly Capacitor – Sense of Accomplishment

Completion of this prototype is a watershed moment. For a few years, I have dreamed about being able to do stuff like this. Gradually, I have learned the electronics, coding and mechanics, and built the tools. Yes, that has cost some money (about $8 a week) and time (maybe 10-15 hours a week) but everyone should have stuff they enjoy doing, right?

I only wish that my grandsons were a bit older and I could do stuff like this with them. Hope that will happen in a few years.

In the meantime, I will get on with building the magnetic loop antenna which will be controlled by the motorized butterfly capacitor. This project needs to be finished before winter.

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