stepper motors glitching

[Swarfing]

Could i suggest you set it off running and then disconnect your screen plus its power supply. I have a similar issue with a dell and it has bad earthing issues from the screen power supply. The interference from these are notorious, could even be the machines power supply chucking spurious outputs all over the place. Worth a punt?

[routercnc]

Hi 2e0poz,

It's a good suggestion, but the monitor is not on at the moment (see previous post). Neither is the PC. To track the problem down I'm running the driver board from a function generator which is providing square wave signals into the parallel socket on the driver board. Therefore the problem must be with the 33v power supply to the board, the board itself (which is a new replacement), or the stepper motor (of which I have 3 and they all glitch in the same way).

But I think you are right in that there must be some kind of interference from something, or bad earth somewhere.

Hoping to have another go at this after work tonight . . .

Barry

[routercnc]

Cracked it !!

Well, I've found the source of the problem anyway. The driver board can take 24v - 33v, so I set up 2x12v 7Ah lead acid batteries to power it by DC, eliminating the 330Watt mains power supply. Now there are no glitches at any speed, from barely moving, right up to 12KHz. I ran it for several minutes like this, changing the frequency on the function generator and it was smooth all the way.

It is remotely possible that the glitching is removed by dropping the voltage (although this doesn't feel like the answer), but I have no easy way to check that since the mains supply only goes down to 33v. Could I use a high wattage resistor to drop the voltage from the mains power supply to 24v to check? What value and resistor type to use if I wanted to try this?

So, I have a square wave function generator, into the stepper parallel port of the driver board, and one stepper motor connected. The board is running from 24v DC and does not glitch at all. However, this is not a long term solution since the batteries are quite small and old and I think they won't take to running the CNC machine.

Now, what is going on here? The power supply was from Roy at DIY CNC and was recommended. Obviously I will email him for advice on this since something about this power supply, or some interaction with the driver board, is causing the glitching, but I'm not electronics expert so need a bit of help.

Can I put ferrite rings around the DC cables?
My VFD came with a mains filter, would this sort of thing help on the main side of the power supply?
What about these choke type devices on the mains side of VFDs?
Could I safely scope the DC voltage to the board provided by the mains power supply to see if there is noise on the supply when the steppers run?

Out of time to try anything more today, but starting the see a way forward!

Thanks
Barry