Now, if that isn’t suspiciously linear, I don’t know what is!
The slope is 0.583 v/(rev/s).
I used the scope’s RMS trace calculator, which smushes out the non-sinusoidal nature of the lower speed waveforms. As expected, there are several nasty mechanical resonances that appear in the output waveform while they’re tormenting my ears:
Top trace is the winding output voltage, bottom trace is the drive input current, plus a line of junk I forgot to turn off.
Drive waveform frequency / 50 = rev/s
Drive waveform frequency * 6/5 = rev/min
So it works. Now I must figure out how to connect load resistors with something more reliable than crappy alligator clips.
This dragonfly decided that the tip of the 2 m / 70 cm antenna on Mary’s bike was the best place around to survey the area; it periodically zipped off to snag a meal, then returned to stand watch again.
Those wraparound compound eyes don’t miss much!
A few weeks ago, a much larger dragonfly bounced off my helmet and snagged itself in the delay line coil near the middle of the antenna: the dragonfly’s head slid 1/4 turn around the coil and latched firmly in place. Amid much buzzing of wings and thrashing of legs, I managed to unscrew the poor critter, whereupon it flew off undamaged.
So the hydration pack I’ve been using for a few years started piddling all over the floor, whereupon some debugging revealed a pinhole leak where the large thermally sealed flange meets the bag side. Nothing, but nothing adheres to the polyethylene (or some such) bag material, but a blob of acrylic caulk (armored with a layer of electrical tape, not shown) may suffice for a while.
I did the same thing to the other side as a prophylactic measure…
Combine two of those mounts with one of those couplers, add two NEMA 17 steppers (the one on the right is that one), slide a baseplate underneath, sprinkle with various screws, and shazam you get a stepper motor dynamometer:
The baseplate puts the mounts 65 mm apart on the 10-32 screw centers, which is entirely a function of the coupler length, and is easy with manual CNC on the Sherline.
Changing the motors is straightforward: loosen coupler setscrew, remove base screws, slide motor away from coupler, remove mount screws. Won’t happen that often, methinks.
The general idea is to drive one stepper with a known current, apply a known resistive load to the other motor’s windings, and then plot torque vs. speed. It won’t be quite that simple, of course, but should produce some interesting data.