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.