stepper motors glitching

[routercnc]

I borrowed a function generator from work yesterday and set it up for a square wave TTL output of 8KHz (=1500mm/min on my system). I connected this to pin3 and earth on the driver board and the stepper motor ran smoothly. I then tried different speeds and at low speeds <8KHz the motors glitched. This was the same result as when the PC is connected whereby it glitched at lower speeds. Although this doesn't rule out the PC glitching, it certainly means that the driver board, stepper motors, or power supply are causing part of the problem and need to be resolved before connecting it back to the computer.

The driver board is a brand new replacement since the previous board glitched (but on the X axis only). The power supply is a 33v 10A unit and is the one recommended by Roy at DIY CNC. This power supply provides 33v (I've checked this with a DVM), which goes through a switch and a current display 0-5A. I plan to directly connect the power to the board to elimate the switch and meter. Next is to double check the wiring to the steppers, but I was very careful with this when I wired them up. Might be getting somewhere !!

[routercnc]

This morning before work I connected the driver board directly to the power supply, thus eliminating the switch and the current display. Again driving directly from the function generator it still glitched <8KHz (i.e. <1500mm/min).

I then checked the connections to the motor and they are all tight. Checked the coil resistance and they both read about 2.8 ohms. I think I read somewhere that this is OK.

I did notice that if the earth connection from the function generator is not made to the parallel port connector, (i.e. only pin3 square wave input is connected) then the stepper motors will still run. This must be earthing through the mains since the power supply and the function generator both run from the mains.

Therefore since the board can run from 24v - 33v, I'm thinking about running it from 2 small 12v batteries in series, as a test. The function generator can also run from batteries. This might tell me if there is some kind of earth loop problem, although Roy tells me that there should not be. The board is not optically isolated.

Are the other users of the DIYCNC system3 all-in-one board out there? What is your set up like?