Stepper drive (Gecko) problem

[LEWENZ]

Hi All:
I've got a peculiar problem with my Mach 3 / Gecko 201 system that I recently got running. The Z axis is unreliable. When I rapid down or up I usually use the Page up/down keys. Something is wrong as occasionally, the Z axis will move in the opposite direction of the keys. I don't have closed loop so the axis position becomes wrong. I've tried many different settings like motor velocity and speed. Also tried setting the step line to active low and high. Nothing seems to make it perform reliably. I've got 201's with a limiting resistor. The motor is a SLo-Syn 300 oz./in. unit. Talked to Mariss when I set it up and he recommended the resistor and a capacitor between the power and common. Doesn't seem to be a heat related issue. Drive is running warm but certainly not hot. Perhaps a noise issue but the other axis run just fine.
Any suggestions?
Thanks
LEW

[CJL5585]

To change the direction of travel in Mach software, change the direction active high/low setting. This should allow the page up & page down keys to select the correct direction of travel.

It is possible that the drive direction pin (5v or 0v) signal is not repeatable or the logic level is at the borderline voltage at about 3.0 VDC if it is intermittant in operation. This is especially true if using a laptop computer without a breakout board that requires an external 5 volt power supply, and one is not using all active low outputs.

Verify operation of present system using g-code commands for the Z axis.

On my system using a Dell laptop, I have experienced problems where the page up and page down keys would not move the axis, but everything works normally while running g-code. Believe problem to be associated with laptop hardware.

[LEWENZ]

Thanks for the reply.
It's not a problem with the direction high of low setting. Most of the time the page up/down key works. I have tried changing the direction logic in Mach also but it malfunctions in both directions. I am using a breakout board and I've checked the voltage from the supply. It's at 5.0v. I'm using a full sized computer - not a laptop. I will check the volts coming out of the breakout board. It is weird that only the z axis malfunctions. I'll check it with Gcode also. Good suggestions.
Thanks

[LEWENZ]

Well, here's what I found for what it's worth. Seems that by slowing the Z axis down the problem went away. I was using a velocity of over 120. By lowering this number to around 70 or so, the motor behaved well and the malfunctioning direction has disappeared. I did do a check running the Z axis with Gcode and with the higher velocity number the Z axis would go the wrong way occasionally. (probably once every 6 cycles)
Just used a G0 Z-1.5, THEN G0 Z0,0. Had those commands repeat about twelve times.
LEW

[CJL5585]

Glad you got the missed steps problem fixed.