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| John Hill:
Hi, Stepconf crashes with a black screen and black and white 'piano keys' over the top quarter of the screen, then a bit of coloured disturbances and back to a black screen. I will have to find how to open a terminal and report back! :coffee: [LATER] I choose 'Applications' and opened a terminal and entered 'stemconf' at the prompt. The program opened normally and crashed normally too! I was left with the 'piano keys' flashing about every two seconds and otherwise a black screen. Obviously I could not see the terminal window... :( [LATER STILL] I changed the printer port definition and no more 'piano keys', not after several minutes of messing around with Stepconf. |
| John Hill:
Now that Stepconf is apparently stable I can continue trying to 'tune' this washing machine motor. The 3 phase driver (the piece of hardware) has DIP switches to set 'steps per revolution', obviously these are micro steps as they range to many thousands starting from 400, presumably this is intended for a 200 step motor. Now I cant see that this hardware knows, or needs to know, the number of steps in the motor which in the case of the washing machine motor is only 42. Stepconf requires me to set 'Driver Microstepping', but why? Surely a 'pulse' signal from the break out board to the stepper controller hardware is one pulse per motor step? There is obviously much for me to learn!!!! |
| vtsteam:
John, steppers can have their coils essentially "rearranged" electrically and the pulses phased to allow micro stepping. It all depends on how many coil wires you have coming out of your motor. There are some advantages to microstepping, even though it would sometimes seem to be unnecessarily fine control of the machine's drive. Here's one discussion of pros and cons: http://www.micromo.com/microstepping-myths-and-realities I'm not sure that one has it completely right. Microstepping can allow the simulation of near sinusoidal waveforms to the stepper motor, instead of square waves. And that is the reason for the reduction of noise and resonance -- those negative factors can hurt a stepper's ultimate performance as much as the necessary reduction in torque he talks about. |
| John Hill:
Thanks, that was a very interesting page to read with my morning coffee. These washing machine motors have a lot of 'cogging', i.e. considerable reluctance to move from one position to the next, so I assume only very low stepping will be possible. Fortunately each of the 42 stator coils is readily accessable and here is an example of the level of modification possible... ....where someone is seeking just the right characteristics for his windmill alternator. Standard configuration is 3 phases where each phase is 14 coils in series, I have modified mine so that each phase is two strings of 7 in parallel which will have reduced the inductance and the voltage. My best theory is that I should go further but 7 is not an easy number to divide, I could make strings of three which would leave three coils unused or I could go the whole hog and make each phase 14 coils in parallel. 14 coils in parallel would surely have very low inductance which does sound like an ideal characteristic for a stepper coil. Presumably the stepper driver could handle the sudden current but the power supply might be a different matter! |
| John Hill:
I got the washing machine stepper going good today although it has taken me a couple of days to find the right number of steps per revolution. I finally found that 112 is the correct figure to set in Stepconf. This figure of course is 8 times the number of coils. |
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