Digital Servo

Hi,

I have not read all, and I am just going to comment on something
from Bertho Boman:

As I said, I can't see that you are doing anything more than what
is common. Someone mentioned the LM628/629, and let us see what
they do.

You send a couple of bytes to it, it has a position feedback,
velocity feedback and acceleration feedback, a very good digital
PID filter, and some other options too. It has modes for filter
updating, resets, home positioning , velocity and position closed
loops. The 628 can drive a H-bridge. Further it has 32bit counters,
I believe. That is more than the STG board. And HP has another
chip, but if my memory don't fail me, it use 24-bit counters.

By the way, I believe the EMC started with boards using LM629 or
similar. You could ask Fred Proctor.

In DSP - there is some other options, and there is chips available
that outperforms a LM629 many times over. But as I said, ask Fred
about it, because the whole idea with the EMC is to overcome some of
the problems using chips like this.

I have also made something similar, - and it was a great educational
experience. A real good demo of my own lack of knowledge ! ;-)

Sorry, I don't want to discourage you. Hmmm....

What if you forget the encoders, and just make a digital H-bridge
drive ? Skip the DAC, PID , etc. Then a 8 bit processor would do
it.
A PIC could do it easy. This could be added to the DRO board that
the others are making, and would fit much better with the EMC
efforts.


//ARNE