RE: [CAD_CAM_EDM_DRO] steppers best?

>I would try unipolar steppers (5 or 6 or 8 wire) and simple
>drivers. By simple I mean two resistors, one transistor and two
>diodes per driver with a current limiter on the common line if
>needed. Need schematics?

The steppers from the fax are 5 wire, and we got them to step with David
Benson's unipolar stepper exerciser. Now we are ready to automate the
stepping process, so yes, we'd love schematics for "simple" driver.

>>2 - Is it pretty easy to do the microcontrolling effort to choose a
>>certain number of steps (DIP switches etc) and then stop, or is this
>>more like an iceberg - a lot deeper than it looks?

>Yes, it is deeper than it looks because there are timing issues on
>the motors. A simple chip like the Basic Stamp (Parallax) will do
>everything you need in a simple language (but slowly!) See
>http://www.parallax <http://www.parallax.com/detail.asp?product_id=27120>

.com/detail.asp?product_id=27120 for the board to

>build your logic and a processor like this one
>http://www.parallax <http://www.parallax.com/detail.asp?product_id=BS2-IC>

.com/detail.asp?product_id=BS2-IC which is easy to

>program. The phase control can be done in one small array and the
>count logic is trivial. The board runs on a 9V battery, the steppers
>on whatever you want to use.

Will look at this, but am thinking we might do a PIC - ??84 on a board??, as
we have a programmer for PIC's already, but with no experience.

>>3 - Other considerations?

>Heat, speed and power come to mind. Running on a surface plate will
>take lots less power than on a carpet. Wheels may be more important
>than you think. Do you need steering? How about avoidance
>sensors? How about an emergency stop button? What are the vehicle

parameters?


Right, can monitor heat part and have a bucket of surplus heat sinks. We'll
be running on hardwood or linoleum, and have 3 sets of wheels, from 9"
circum to 20"ish, so should be good to go. We'll do dead reckoning - just
straight line for 5 - 10 M right now. No obstacles this go either. Estop
might be good idea. Vehicle 40 +/- 3 cm 16" ish long, by 25 +0 - ?? 10"
wide. Task = pull out of impound, 10 minute participation clock starts, set
vehicle for announced distance, predict time to distance (from previous
calibration), placed on start line and pointed with intact pointing device,
to be turned on with pencil or stick, autonomously travel specific distance
between 5 and 10 m (needs to be calibrated before hand), stop. 3 scoring
components = distance traveled vs desired distance and distance offline and
predicted time vs actual time (have up to 45 seconds to travel the distance
(max 10 m))

David G. LeVine
Nashua, NH 03060
THANKS! Chuck


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