Testing of the preliminary switchmode converter worked well, but after braking too hard while going too fast, the plastic sprocket shattered. Probably because the M4 screw bent, but I think it needs a metal sprocket instead. Unfortunantly the only metal sprocket for this type of chain I have is the one already on the bike's wheel, so I needed to drill one out on the drillpress and round it off with the dremel.
After many hours of tedious drilling and grinding, the sprocket is finished. It works well.