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General Mach Discussion / Re: Mach2 inconsistent motor drive pulses
« on: October 15, 2008, 03:51:11 PM »
Thanks for the replies everybody.
HimyKabibble: Actually, I did say what the CPU speed was. And how much memory my machine has. I've tested on two machines with greater than 2GHZ clock speeds with 4GB of dual channel fast RAM.
RICH: I hear ya. But I don't have much money, and I do have a bunch of electronic stuff lying around that I can use. Plus, I like making my own stuff because it does exactly what I want it to do.
da21: I haven't compared pulses from the output of the parallel port to the output of my isolator. I didn't think it was necessary since the 2631 is a 10MB logic chip with rise and fall times of 60ns typical. The 74ls244 is 6ns. That's alot faster than Mach runs at. But you are right, there could be a problem there so I will check it out.
I have a 48VDC, 12.5A power supply. The motors are rated at 2.8A. I'm running them at 2.4A right now.
I'm not using pullups on the buffer ICs, just on the optocouplers. I went without pullups on the buffer input to keep the current draw from the parallel port to the absolute minimum. The 74ls244 is only supposed to draw uA. But I guess I assumed that the parallel port outputs would be pulled up internally. My mistake.
I didn't use pullups on the buffer outputs because the chip is supposed to be a balanced current source/ sink. The internal circuitry either turns on a transistor to ground or a darlington to Vcc. I guess again I assumed that one of those would always be on. However, judging from the scope trace, I don't think the buffer output is sufferring any tri-state issues because it would have enough current to turn on the couplers and I'd have alot bigger pulses. I'd post the schematic but it's pretty big.
Thanks for the ideas. In the near future I will be trying to run Mach on a stripped down fresh install of XP, but right now I don't have a computer that I can use for that. I have the case but none of the guts yet. I hope that will fix my problem.
HimyKabibble: Actually, I did say what the CPU speed was. And how much memory my machine has. I've tested on two machines with greater than 2GHZ clock speeds with 4GB of dual channel fast RAM.
RICH: I hear ya. But I don't have much money, and I do have a bunch of electronic stuff lying around that I can use. Plus, I like making my own stuff because it does exactly what I want it to do.
da21: I haven't compared pulses from the output of the parallel port to the output of my isolator. I didn't think it was necessary since the 2631 is a 10MB logic chip with rise and fall times of 60ns typical. The 74ls244 is 6ns. That's alot faster than Mach runs at. But you are right, there could be a problem there so I will check it out.
I have a 48VDC, 12.5A power supply. The motors are rated at 2.8A. I'm running them at 2.4A right now.
I'm not using pullups on the buffer ICs, just on the optocouplers. I went without pullups on the buffer input to keep the current draw from the parallel port to the absolute minimum. The 74ls244 is only supposed to draw uA. But I guess I assumed that the parallel port outputs would be pulled up internally. My mistake.
I didn't use pullups on the buffer outputs because the chip is supposed to be a balanced current source/ sink. The internal circuitry either turns on a transistor to ground or a darlington to Vcc. I guess again I assumed that one of those would always be on. However, judging from the scope trace, I don't think the buffer output is sufferring any tri-state issues because it would have enough current to turn on the couplers and I'd have alot bigger pulses. I'd post the schematic but it's pretty big.
Thanks for the ideas. In the near future I will be trying to run Mach on a stripped down fresh install of XP, but right now I don't have a computer that I can use for that. I have the case but none of the guts yet. I hope that will fix my problem.