Homebrew PCBs

Brian,
      The Tip120s have a built in damper diode. You can find
some info at:

http://www.luberth.com/plotter/plotter.htm

    Check out GRANT's circuit in the left side box. 


                                      John






--- In Homebrew_PCBs@y..., Brian Gracia <bgracia@b...> wrote:
> Hello Everyone,
> 
> I need some help starting out with CNC.  I am going to build a CNC 
router 
> type machine to route pcbs.  I need some help with the circuits.
> 
> I have 3-60oz in stepper motors I got from HobbyCNC.  They are 
marked 
> STH-55D203-02 1.8 deg/step, 5.1V 1A. I believe they are unipolar 
from the 
> docs and they have 6 leads coming from them. This is my first 
adventure 
> with controlling stepper motors.  I have another project for CNC 
when I get 
> finished with this one.  My mother (I am 34 as of Sunday) wants one 
of 
> those embroidery sewing machines that cost $3000+.  She want's to 
do some 
> sewing designs and monograms on clothes.  If I get my CNC 
router/driller 
> working, I am going to attempt to build her one with the other 
group of 3 
> unipolar stepper motors I have.
> 
> I went looking for ICs to control all of the stepper motors I 
have.  I have 
> a total of 6 motors, 3 being of one make and spec, and the other 3 
being of 
> another make and spec.  Each group of 3 motors is the same spec, so 
I do 
> not have to worry about trying to control motors of different 
> characteristics.  I found the UCN5804B to be a good chip, but it 
will not 
> meet the power specs of both stepper motor group I have.  They have 
> different current ratings.  One group is 1A, the other 1.44A.  So, 
I will 
> need some transistors that can interface with the 5804B so that no 
matter 
> which motor group I am using, the circuit will power them.
> 
> I found the TIP 120 to be able to put out up to 3A, which is more 
than 
> enough. Page 5 of this 
doc:http://www.alltronics.com/download/5804.pdf 
> shows the circuit I would like to build.  I know that I will need 
the 
> diodes as circuit protectors.  Can anyone show me how to hook up 
the Tip's.
> I had lots of theory 12 yrs ago in college, but could not graduate 
do to 
> not being able to pass calculus.  They blocked me from taking my 
Senior 
> level classes.  So I wasted a lot of money!
> 
> I did an extensive search on the net and came across several chips, 
but 
> would still need the extra transistors to power the more current 
hungry 
> motor.  Also, these chips were more expensive.  It is not that I am 
being 
> cheep, I could purchase a board which many on this group seem to 
sell, it 
> is just that I wish to learn more about electronics.
> 
> I am looking to purchase the chips this week, so I anyone could 
help me 
> out, I would appreciate it.
> 
> Thanks,
> Brian G.