University Digital Electronics Class Project.

[wholepair]

I'm planning a project for my digital electronics class - I have three stepper motor driver IC's from AllegroMicroSystems and am reading through the spec sheets now to plan my attack.
http://www.allegromicro.com/sf/3967/
http://www.allegromicro.com/datafile/3967.pdf
http://www.allegromicro.com/demo/a3967slb/schematic.pdf
Im "not" planning on building a machine, this is primarily a project that envolves the electronic/digital end only. If I do any machanical work it will be a simple lead screw to stepper motor mount that moves a table thru a small distance with a limit switch at each end. I will do this for each of the three motors in a very simple(hacked) manner. What I want to end up with is one board that has the three chips and all the other necassary electronic components with locations to jack in the step and direction signals and a way to accomodate the limit switch logic states. My intuition is I will be able to work through most of that on my own. What I would like to ask is:

Is it possible to build a jog handwheel from a small floppy drive stepper motor that would, when turned by hand, produce the step and direction signals that go to the motion control board I make. I hooked up one of these motors(TEAC P#-14769070-90) to an osciliscope and can see the signal it produces with hand powered spinning. Moving only small single increments produces a very faint signal. Real quick turns produces a max of 3 volts from what I can see. I consider this to like an analog input and think I need to create my own DAC to send to the S&D logic on the motion board. An engineer that works at the university said he read an article on doing just this, but can't remember where. I searched around for info - but only found a bunch of Sherline crap . I will talk to him again next week, and show him the signal I produced on the osciliscope, he might have figured out how to do it by then, but I would greatly appreciate any
in[put I could get from you folk.


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Any kind of project idea for the step and direction signal generation would be appreciated. I could easily just wire up a toggle for the direction and have a button or variable speed clock stream for the rising edge step signal. I could even just use Qbasic or a premade software package like Mach2. I heard of people modifying video game controls to produce the signals. What would be real cool would be to modify a mouse to do it. I like the stepper motor idea because it resembles a CNC style pendent like handwheel.

[abasir]

Go here for floppy stepper to encoder description, schematic and layout.
http://www.webx.dk/oz2cpu/20m/encoder.htm

[fyffe555]

trying to use a stepper to generate signals will require a stage to clean up the pulses from the stepper and to convert them to an acceptable hi/low. This would also only produce the step signal not the direction.

Much better, and a digital electronics solution if all you want is a step stream is to use a 555 and vary the speed with a pot on the resistor/capacitor selection controlling the 555's stable rate and a simple switch to set hi or low for the direction state.

theres a lot of that sort of stuff on schematics for stepper drivers on the web. Look at kit 109 from www.kitsrus.com http://kitsrus.com/pdf/k109.pdf for an example

Andrew

[wholepair]

Thank YOU - the link from abisir is terrif - Im going to try to build it up on a small bread board and test it - Thanks again!

[H500]

Why not just buy an encoder from digikey? They cost less than a surplus stepper and will produce a cleaner signal.

Since you're learning electronics, why not use an 8 pin microcontroller to translate the signal. The atmel AVR is very easy to use.