Minimal system to control steppers \ servos ??

[jahcure]

Hi im pretty new here and i have been reading on how to diy 3 axis cnc but since i am studying in electronics at dawson college i have to build a microprocessor as part of my final year project
its max 20mhz and 1 meg ram im really not sure of the capabilities of this system but here is a link to the specs http://volta.dawsoncollege.qc.ca/co605.html the essence of my question is that i want to build a 3 axis cnc and would like to use this microprosessor as a controller for stepper \ servos is this possible ? i know that the microprosessor will be interfaced via hyperterminal to load files to it. i spoke about it to my asembly language teacher he told me that i would need a program that would convert the g-code and then send it out via the microprossor parralell ports. But i dont know were to start Any pointers

all help is apreciated

Thanks

[pminmo]

hi jahcure,
You can control 3 steppers with your system, with adding to power drivers for the coils of a stepper motor. You can also do servo's, but it becomes more involved. Browse my website and you may find some information that helps. http://pminmo.com

[jahcure]

Thanks you very much but humm that was not really my concern it was more on how do i get to interface this minimal system meaninng it does not have dos or anything so i guess i need to get or programm a g code converter for it and thats where im stuck

[pminmo]

My suggestion would be since it and 8088 based board would be to look into a minimalist linux os such as puppy, dsl, or mulinux and emc2. It may be a stretch, and would definitely require some effort. Thus you would be creating an embedded machine controller that would execute g-code. Or dos and turbocnc running on the 8088. Either way you would require a couple of megs or ram, but you would benifit from having the g-code controller turn key. But it would be simpler to find and old pc that somebody thinks is outdated for free and use it.

[jahcure]

i agree but since my first intentions was to use it for school project it would of been great im sad thats its kinda limited tough cause since ihave to program the 8088 from scratch making a cnc out of it would of been neat

Thanks for you help

[Episs]

how match peripherals your 8088 MCH have? sutch ase PWM chanels, Timers, input capture, compare chanels.
I ask becouse it would be hard to make simple code without these chanels for example for step/dir signal PWM generation (wehn you will decode G-code) or for Quadrature encoder decoding without Input capture chanel it would be harder to decode and if these periferals are not in MCU hardware then to make them in code it will consume lot of MCU instructions and time so you will get slow CNC controller.
You could make system were one 8088 Mcu is for one motor then it will be mutch esier and faster.

[jahcure]

Thanks for your concern but actually it is a mpu and not a mcu so according to my teacher all these PWM chanels, Timers, input capture, compare chanels. i will be able to add them sepratly. if your intrested in helping futher more, information on the device it self can be found here : http://volta.dawsoncollege.qc.ca/co605.html

Jahcure

[Willbird]

I am pretty new to this stuff, so ignore my rambling if it is insane. But DOS is not a multi-task OS right ??

That aside, depending on what kind of control you need, I'm wondering if you could send the X axis direction and a number of pulses, say 500, then send the same data to Y, then send the reverse direction and the same number of pulses to X, then Y. The table would move in a square. ?? The exact timing would not be so critical then, as it would not be multitasking ??


Bill

[pminmo]

I am pretty new to this stuff, so ignore my rambling if it is insane. But DOS is not a multi-task OS right ??

That aside, depending on what kind of control you need, I'm wondering if you could send the X axis direction and a number of pulses, say 500, then send the same data to Y, then send the reverse direction and the same number of pulses to X, then Y. The table would move in a square. ?? The exact timing would not be so critical then, as it would not be multitasking ??


Bill

Multitasking is not a requirement, and in fact can be a source of a problem. Since most of the cnc cam software uses step-direction signals from the same parallel port, the 8bit data becomes one datastream, and the processor is making decisions based on cpu timing.
For example say your drawing a 45 degree vector, the x and y axis are stepped at the same rate, and that rate is based on the computation of the mechanical characteristics, step rate, feed rate. As you move the angle of the vector off 45, one axis gets step pulse(s) when the other doesn't. Think of it as fractional time.