Homebrew PCBs

On Sat, 11 Jun 2005 04:03:42 +0200, Robert Hedan  
<robert.hedan@...> wrote:

> We're still here; either waiting for another member to move along on his
> driver design, waiting on parts or workin on the structure for the most
> part.


I would have been done with my driver design by now, but sadly i have lost  
my HDs and all the nice files and PCB layouts are lost. Why don't you make  
your own driver, it is not that hard? Divide it in two sections, control  
and power, this way you can accomodate additional or different motors  
easily (no. of phase etc..).

The brain can be whatever you like, i suggest a CPLD like the ones from  
xilinx. they are easier to programm than a micro, and are ideal to do many  
things at the same time (you can easily run 5 axes with one cpld). Should  
you not be familiar with CPLDs, they are basically chips with many pins  
where you can programm in whatever logic you want.
But you could also use microprocessors or even simple 74xx logic to make  
the brain.

The power modules would have the driver transistors, and also comparators  
to form closed loop control of the current in the winding. That means  
you'd supply them with a voltage, like 0-5V, and the drivers would  
translate it into 0-5A or whatever on their own. The brain does not need  
to get feedback in this case, which makes things much easier.
To make microstepping you simply programm two coils with different  
percentages of the full voltage.
When the power modules do all the chopping, it is very easy to have them  
show a ideal current rise-time (full on as long as current has not reached  
set value), for fast speeds.


ST