Re: stepper issues

If you're using the 555 monostable to program your distance you probably
will not have very good accuracy or repeatability. The R/C components
required for that much delay will have fairly large deviations from their
rated values, and will be difficult to callibrate. I would suggest using the
astable 555 to generate step pulses for the motor driver, and using a
digital counter preloaded from dip switches to set the step count. This will
give you pin-point accuracy.

The problem with the motors could be the relatively low voltage you are
using for V+. The 5804 does not do any microstepping, so you are vulnerable
to mid-range resonance problems. Try experimenting with various step rates
until you find one that works well. As a rule, slower rates will give more
reliable performance, so go as slow as you can. If you need speed as well as
accuracy, I would use a regular DC motor to drive the wheels and an encoder
to measure the distance, with some sort of brake at the end.
--
Phil Mattison
http://www.ohmikron.com/
Motors::Drivers::Controllers::Software

----- Original Message -----
From: ebiz_59 <chuckm@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Saturday, November 17, 2007 6:09 AM
Subject: [CAD_CAM_EDM_DRO] stepper issues


> Thanks for all you help so far. I'm working with a high school
> freshman to get a stepper motor to run a certain number of steps and
> then stop - calibrate a small erector set car to run between 5 and 10
> meters (we'll be told specific distance at the competition) and then stop.
>
> We have combined 2 basic circuits to accomplish this task - a 555 as
> monostable (adjustable time) dumping into a 555 astable to give steps
> while monostable is saying "go" and the astable dumps into the trigger
> of a 5804.
>
> We get this circuit to drive a stacked can motor - we need like 30 to
> 45 seconds of run time. We don't have it hooked to the device yet -
> the motor is just driving another free running gear. The motor starts
> alright, but sometimes well into the run, it gets confused and
> stalls/reverses.
>
> A few notes about stuff we might have done wrong -
> 1 - we didn't use pullup/down resistors for the full, half, direction
> pins - we just tied them to +5 or gnd.
> 2 - we hard wired this on an soldered experiment board and have wires
> going everywhere. We initially did 3 circuits on 3 separate
> breadboards and had the same problem. I thought it might be the
> breadboards and the fact that we could only put about 7 V to the motor
> circuit, but we get the same results with a wired cicuit all on 1
> soldered breadboard and 9.6 V battery running the motors and dropped
> down through a 7805 to run the 555's and 5804.
> 3 - we are limited to 9.6 V max by the rules
> 4 - we didn't use a PIC for a couple reasons - I wanted him to learn
> about 555's, we didn't have PIC programmer in stock so I thought I'd
> have him work on the 555 path while I researched and acquired
> programmer - still hope to do this, but the competition that sparked
> this project is Tues, Nov 20, so we are trying desparately to get this
> circuit to work.
>
> We'd sure appreciate your help in where to look.
>
> Thanks again for your help so far, and for any you can give over the
> next few hours/days.
>
> Chuck
>
>
>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html
> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com
>
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...,
timg@...
> Moderator: pentam@... indigo_red@... davemucha@...
[Moderators]
> URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if
you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a
sister site to the CCED group, as many of the same members are there, for OT
subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> bill
> List Mom
> List Owner
>
>
> Yahoo! Groups Links
>
>
>