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General Mach Discussion / wrong activelow
« on: December 08, 2011, 02:13:55 PM »
I verified that the activelow and activehigh are reversed in the manual, and in Mach3 (latest and 3 years ago versions). Running W2000, kernel speed is either 25k or 35K, mostly higher values don't work.
Background: Standard true ActiveLow means the line is normally high, then a step is activated when going low. Mach3 manual and Motor Pins are the opposite. Best performance and noise immunity occurs when using true ActiveLow (line is normally high), then the cable has +5v noise margin all the way down to +.8v or sometimes .6v. If one uses true ActiveHigh, then the cable is sitting at around .2v to .5v, depending on the driver, it can never be lower than .2v. Thus true ActiveHigh only has about .4v noise margin, and often spurious noise on cables longer than 3 feet can easily generate false or missing steps (even if cable is shielded), that's why true ActiveLow is used throughout the electronics industry.
Until we made X & Y Motor Pins active high, the motors moved 40% or 63%, and other values caused different physical movements. We also noticed that when we selected ActiveLow, the physical distance traveled depended on the acceleration and velocity values. Travel was consistent, but always wrong. Then making the X & Y Motor Pins active high (right situation but wrong description according to Mach3) fixed the wrong movement--now 1" = 1".
I note that the Z axis had the opposite effect from X & Y. Z axis only works well if ActiveLow is selected. When Z has ActiveHigh, the travel was exactly half. so we tape a large warning on our mills--select ActiveLow for X & Y, select ActiveHigh for Z.
It is possible that these Mach3 software issues are only due to our values, but we actually tried a full range of values for distance, velocity, accel. Mach3 should never have a different travel distance just by changing the acceleration or velocity values. We came across this activelow/high issue 6 years ago on another machine, made it work, and imachined thousands of parts. I now wanted to write this help all. I can imagine many Mach3 users just giving up.
Background: Standard true ActiveLow means the line is normally high, then a step is activated when going low. Mach3 manual and Motor Pins are the opposite. Best performance and noise immunity occurs when using true ActiveLow (line is normally high), then the cable has +5v noise margin all the way down to +.8v or sometimes .6v. If one uses true ActiveHigh, then the cable is sitting at around .2v to .5v, depending on the driver, it can never be lower than .2v. Thus true ActiveHigh only has about .4v noise margin, and often spurious noise on cables longer than 3 feet can easily generate false or missing steps (even if cable is shielded), that's why true ActiveLow is used throughout the electronics industry.
Until we made X & Y Motor Pins active high, the motors moved 40% or 63%, and other values caused different physical movements. We also noticed that when we selected ActiveLow, the physical distance traveled depended on the acceleration and velocity values. Travel was consistent, but always wrong. Then making the X & Y Motor Pins active high (right situation but wrong description according to Mach3) fixed the wrong movement--now 1" = 1".
I note that the Z axis had the opposite effect from X & Y. Z axis only works well if ActiveLow is selected. When Z has ActiveHigh, the travel was exactly half. so we tape a large warning on our mills--select ActiveLow for X & Y, select ActiveHigh for Z.
It is possible that these Mach3 software issues are only due to our values, but we actually tried a full range of values for distance, velocity, accel. Mach3 should never have a different travel distance just by changing the acceleration or velocity values. We came across this activelow/high issue 6 years ago on another machine, made it work, and imachined thousands of parts. I now wanted to write this help all. I can imagine many Mach3 users just giving up.