RUIDA RDC6445S Firmware V26.01.16
Chuck style rotary run by swapping Y axis connection to rotary device.
When swapping to rotary setup, my present method is to “load from file” the set of parameters that suit my rotary.
Power down machine.
Swap in the rotary by plugging the Y axis connection to rotary and power up again.
The process in reverse when swapping back to standard X/Y.
There is probably a smarter method of doing this. Any one have some advise?
That’s harmless almost all the time. When it isn’t, the motor driver dies.
Each phase of the usual H-bridge bipolar driver has current flowing through the motor winding and two MOSFETs. When you unplug the stepper motor with the winding energized, the energy stored in the winding inductance produces a (sometimes small, sometimes large) arc between the connector pins. The arc voltage appears across the two MOSFETs conducting the current, raising the high side MOSFET hundreds-to-thousands of volts above the low side MOSFET.
Air has a breakdown voltage around 1 kV/mm. The voltage across the arc drops when it gets up and running, but the damage happens at breakdown. This is all fast enough that the usual assumptions about power supply capacitors, decoupling, and suchlike don’t apply.
The arc voltage pushes the high side MOSFET far above the motor supply voltage, with the current continuing to flow toward the low-side driver, so its body diode does not turn on. The upper MOSFET shuts down as its source voltage rises above its gate, the winding current pushes its body diode into breakdown, and the supply voltage steps upward by another hundred volts or so.
What happens next depends on a bunch of imponderables (usually the phase of the moon and definitely recent karma), but AFAICT the upper MOSFET and its gate drive circuitry generally takes a hit as the semiconductor insulation layers break down.
Again, mostly this doesn’t happen. When it does, the driver is trash and, if it’s one of those fancy all-in-one controller boards with SMD MOSFETs, the whole board is trash unless you’re a dab hand at PCB rework.
The risk-to-reward ratio is much like eye protection in the shop: sometimes you’re really really glad that sliver stabbed your goggles.
That’s ok, I get hammered every time I mention that I do that, but it’s still up and running… knock on wood…
I’m also sitting on a hardware replacement for the driver…
Don’t really trust the Chinese manual on the output of the Ruida… they show it going through an optical isolator driving a solenoid. I know of no optical isolator that will allow 500mA… we know they drive some kind of N channel open collector type output. Many have replaced them…
I know what you mean about the diodes, I bought a package of 100 just to get 2, and they’re still sitting on the bench next to my laser. One of these days. You provide good counsel to those of us seeking it, and we appreciate it. Thank you.