Originally Posted by noisillator  Are you using the unregulated supply suggested by HobbyCNC? A full wave bridge with a 24V transformer will produce about 34VDC, but that's only with no load. The output voltage of an unregulated supply can drop quite a bit depending on the current draw, filter capacitance and transformer sag. Worst case, it might be pulled all the way down to 24V or less. I'm thinking I'll want to power this project with either a regulated linear supply or a switcher rated 36-40V. Maybe that's what you're doing (?) |
Yes I'm using a regulated 36v power supply, if you can find a 40v, go for it
As far as the harmonics issue, there are two ways to get rid of it one is a mechanical dampener which is basically a disk thats built a lot like an old steam engine governor. Typically they seem to have 2-3 weights that move outward as the stepper spins up. Basically they're just added dampening mass.
It can also be dampened electronically. Basically (...I think...) as the rotor in the steppers start to speed up the phases in the mid band range end up being 180 degrees out of sync, so the flux ends up building at a certain harmonic, this can in fact knock the entire rotor out of sync, or at the very least reduce its over all torque. I'm not entirely sure how its dampened, but I'd imagine the gecko's do it by watching the EMI off the windings, when theres a condition for resonance it may temporarily increase the current to the current driving windings to give it the extra power it needs to overcome the resonance but I have no idea honestly.
Once the rotor is moving fast enough, there is enough stored inertia in the rotor to overcome the resonance and at extremely slow speeds the flux has time to dissipate before effecting anything.
This is kind of a problem with the hobby cnc's, for instance my machine gets extremely rough around 3-5ipm and its very easy to stall. It stays rough up until about 12ipm where the steppers start sounding smooth again. 1-2IPM is also very rough, but theres a lot of torque.