Re: ATM motorizing scope questions

["Bob May" <bobmay@nethere.com>]

<<Hi Bob,
I did a test, of sorts, to determine the torque of the motor.  This only
covers hi speed torque however.  I checked the resistance to being stopped
when it was connected to the circuit and when it was wired direct.  It was
substantially the same.  Low power, I don't know about, however, this
circuit board is 3 inches by 5 inches and everything on it is separated by
about an inch from the nearest part. Don't know if it makes any difference
but it is hard wired.  I used 22 gauge wire since I haven't got a clue about
making a printed circuit board beyond the basics of the fact that what you
want to keep is covered, and what you want to remove is etched off.  How to
layout a printed circuit and then etch it was more than I wanted to tackle
just yet.
I still have to build a reduction gear box, which I do know how to do, if I
can just find a good source for the gears I need.
Thanks, Jerry
>>
The 22 gauge wire is fine for carrying a signal about but you are going to
have to replace (just add on for your completed circuit) a heavier wire like
16ga. to the power stuff going to the motor.  This will keep things from
going bonkers.  Also, any caps. that are across the power supply need to be
near something.  The idea of putting several little caps. in a circuit is
foreign to amateurs of electronics but you will see that there are some .1uf
or so caps in the drawing?  There should be several and instead of putting
them all together at one point like many would do, you need to put one of
them across any ICs power supply leads as this provides the isolation needed
on the power supply for noise getting at the internals of the IC.
I'll also note that stepper motors have a max speed that they will go and
that happens when they can't take the power that is being fed them (remember
that a stepper motor is a bunch of inductors for the windings!) because the
current doesn't get up to where the winding is saturated with the current.
Get the rotation rate high enough, and the motor will stop and just vibrate.
until it gets to that point, the torque will decrease from some speed.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
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