Re: [CAD_CAM_EDM_DRO] USC of Jon Elson

Jon:

Jon Elson wrote:

>alex wrote:
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>
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>>Understood.
>>Bur should I in this case count pulses to know when to stop?
>>
>>
>>
>>
>Well, the CPU can't see the individual pulses, and has no idea when they
>are coming out. What it DOES have is a continuous reading of the
>current position. But, you can't just turn it loose until the position
>count is what you want, and then abruptly stop. The stepper motor
>will skip steps, and end up moving a little further than you want.
>You have to ramp the speed up to some reasonable rate, cruise
>at that rate until you get within some range of the stopping point, and
>then ramp the speed down, until you arrive at the stopping point and
>with a velocity of zero. You can't do this with a simple loop in
>software, it takes several loops, and probably a state machine type
>of architecture. Having a real time clock to schedule the loops
>gives more predictable control.
>

Can't I get away with one loop in a case of low speed and low
intrtial load? This would be nice at least for
hardware testing. Then I could build on it...

>
>This all assumes you are talking about using my board. If not, you
>really have to do all the same stuff, but you have to generate the train
>of step pulses, too.
>

This is good - no pilse train!

> You really need a real time system, or to be totally
>sure that there are no OS routines that will steal time from your loops
>to make your step pulses have timing jitter.
>

Dos is cheap enough for me!
Alex

>
>Jon
>
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