I can check my dynamo works by spinning the wheel on the workstand or just riding, but I'd like to do some more involved testing. I'd like to develop some custom electronics to use the extra power available at high speeds (for charging), to drive an additional rear light that's always on even if the front light isn't, etc. The first step is to measure the output. I can make a start with a battery oscilloscope in my top tube bag, but that won't get me very far.
Road speed is something like 300 rpm, and I can't achieve that by just spinning the wheel by hand, let alone work my oscilloscope at the same time, so I'd like a hands-free solution. Ideally this would work on the bike, as I'd like to try this with the existing lights as well.
I have tried running the chuck of a cordless drill against the front tyre, handheld. The speed ratio should be about right given the diameters of the chuck and wheel, but there's too much slippage from the hard curved plastic. Something cheap and easy to fit/remove would be ideal.