Stepper motor working in 1 direction only!

[davidc]

Hi All, new to MACH3 & CNC control in general, so hoping I've just got something silly wrong here!

I've got a stepper motor (Bipolar) connected to a Parker XL25 driver, connected to my PC & MACH3.

The driver can operate in 2 modes, Step/Direction, or Step+/Step- mode.

wired for step/direction, I have ports 1&2 on the LPT connected to the corresponding step/dir ports on the driver, but although the motor powers on I get no motion.

Someone suggested that by switching to Step+/Step- mode (there is a DIP switch on the driver to do this) and just wiring the Step- & Dir - pins on the driver together it would work.
Now I get motion in one direction only (presumably caused by the inputs on the Step+ & Dir+ pins, but lacking any input on the Step- & Dir - pins)
Is it possible to configure MACH3 to operate in this Step+/Step- mode, or any trick to get the Step/Dir mode working?

Many thanks for any help - much appreciated!

Dave.

[Tweakie.CNC]

Hi David,

Welcome to the forum.
I have not actually used the XL25 I am just going by the manual but it would seem that the XL25 inputs should be connected;
Pin 1 to computer LPT pin 2
Pin 2 to computer LPT pin 3
Pin 6 GND
Pin 7 GND
And mach configured (active high) something similar to attachment (it is not usual to use Pin1 of the computer LPT port for step and direction signals)

Now this should work but it is not the preferred way to do it because the computer’s LPT port can sink more current than it can source. Either (a) connect Pins 1 and 2 of the XL25 through current limiting resistors to +5 volts and use pins 6 and 7 as active low inputs from the LPT port pins 2 and 3 or (b) use an active breakout board which can provide the TTL level signals to the XL25 without loading the LPT parallel port.

Tweakie.

[Hood]

Personally I would make up (or you could buy) a line driver to change the Step/Dir single ended signals out of the PP into Differential.
Hood

[davidc]

Thanks for the replies!
Will have a go at shifting the pin assignments to 2&3, though should it make much difference if I've specified pins 1&2 in the outputs of MACH3?

When you say pins 6&7 to GND, is that simply left disconnected, or is there a specific place/pin I should attach those wires to?
Sorry if the questions sound stupid, this electrickery is all new to me!

Many thanks,
Dave.

[Tweakie.CNC]

Dave,

Pins 6 & 7 are the low end of the opto isolator circuits and they should be connected to Ground or 0 Volts (pins 18-25 of the LPT port if you are not using a breakout board or 0 Volts of the active breakout board supply).

Tweakie.

[davidc]

Thanks for the edit, just had to google that one ;-)

Will have a go at that now & see how it goes!

Cheers,
Dave.

[davidc]

Many thanks for the help guys, thats working perfectly now!