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DPRG: Comment and Transister Problem -- Help

Subject: DPRG: Comment and Transister Problem -- Help
From: TopOne top.one at usa.net
Date: Thu Jul 24 15:05:25 CDT 1997

> > From: Rick and Debora Everett <DebEverett at pobox.com>
> > To: srs at seattlerobotics.org
> > Subject: Couple of interesting items in flyer
> > Date: Wednesday, July 23, 1997 8:45 PM
> >
> >
> > Hi again.
> >
> > Just thought I would let you know there are a couple of
> > interesting items in the new BG Micro sale flyer.
> >
> > Robot Gear Motors:
> > no load 100mA, 250mA moderate load (what is a moderate load???)
> > 12 or 24 volt. Motor size is 1.5" by 3.25"  Output shaft is
> > .375".  No load speed at 12 volts is 48 rpm.  9.95 each or
> > 4 for $34.

I picked up one of these motors to play with yesterday.  Since B G Micro
did not have anu 7486 X-or chips I went to Tanners to pick some up. I
saw what appeared to be the identical motor for $8.95 at Tanners.  

> >
> > Power FETs  IRF540 special $.39 each.  (That speaks for itself)
> > Build those high current stepper drivers!
> >

I also picked up some TIP32 NPN transistors for my stepper motor.  I
have been working on it all morning, and can't get it to sink correctly.


                       c|------ Meter ------  +12 VDC
                       /
                     |/
                     |
       990 Ohms     b|
- --------\/\/\/\------|  TIP32
 TTL  Hi, Lo         |
 +5, 0               |\
                       V  
                        | e
                        |
                        |-------------------  -12 VDC
                      -----     
                       ---
                        -

What am I missing here?  The meter is where my motor should be. I am
getting about 2.1 V independent of the TTL level on the base.  I know I
should have 1K resister, but since I did not, I used 3 330 Ohm resisters
in series.  Is it really that sensitive?  Am I making a fundamental
mistake?  I will stop by Tanners for some 1K Resisters today.
                  _______
TIP32 From Front  |  O  | Heat Sink on Back
                  |_____|
                  |     |
                  |_____|
                   | | |
                   | | |
                   | | |
                   B C E

Regards,
Kip





 

> >
> > Richard
> >

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