Universal Stepper Motor Controller

Philldapill

Here's an idea I'd like to just toss out there and see what I can catch.

I recently aquired over 200 various steppers - some large, some small. I've been toying with them, getting them to move, seeing how much torque I can get, etc. However, it seems many of these steppers have various wires, and various configurations. Dun-dun-nun-nah! Sounds like a job for the propeller!

I'd like to design a universal stepper controller that would have the following characteristics:

1. Be able to hook up many stepper motors - as many wire connections as possible.
···· a. Having these many connections, be able to hook them up in various configurations such as 2phase, 4 phase, bipolar, unipolar, 4/6/8 wire, etc.
···· b. Have individual H-bridges with fair load capacity(2A or so) that are independent of one another
2. Have a fairly simple setup interface consisting of a TV ouput(or vga but that may be more pins, haven't looked into it), and a keyboard input.
···· a. The tv would obviously be for viewing the setup utility, and keyboard for modifying
···· b. Be able to tell the controller what phases are connected where, and what stepping sequence to go through
3. An I2C interface which I believe only consists of a clock and data line, with the clock being used by many devices
···· a. Possibly a simple data stream interface where you send bit streams as commands
········· i.e. "Move Stepper A forward"..."Move Stepper C backwards"... etc. etc.
···· b. Maybe some manual override pushbuttons or connectors that when held, continually move a stepper at a pre-programmed speed(able to modify via setup utility)


I know there are some technical issues with this, and will probably be very strapped for pins, but I think using some Serial to Parallel IC's on the board to free up I/O's would help. In addition, I could probably use some of those L298N chips for smaller scale power boosting. I've posted quite a few times on here before and really appreciate everyone's input whether you think it's much or not. So, thank you all in advance.

Philldapill

Well, here is a simple circuit that I THINK gives a fairly constant current, independent of the time on for each phase. It's an H-Bridge somewhat based of off Joerg's design in an earlier post(thanks!). I think the two opamps will watch the voltage drop along the shunt resistor, and boost the voltage applied via the transistors at the start of the turn on phase, and tapering leveling off the voltage when the current is flowing. The two signal generators are feeding the Op-Amps with inverse signals so that they aren't active at the same time. Suggestions more than welcome.

Post Edited (Philldapill) : 2/12/2008 5:06:13 AM GMT

Philldapill

I'm starting to think no one would be interested in one...?

Joerg

Hi
please do not use OPAMP's as comparators! Especially those like the well known LM324 do NOT work near groundlevels ((0..1V).
Please use comparators like LM2904. This circuti is working down to GND and is pretty fast also!

Saluti Joerg

PS. Why not work on MoCo together?

Graham Stabler

Is there a need for a universal stepper drive with visual set up considering most people don't have 200 stepper motors and there are really only two types of interest. Step, direction and current setting resistor seems as complicated as it needs to be.

Beware that the motors don't become your hobby rather than being a component used in your hobby. Don't ask how I know of the danger of that [noparse]:)[/noparse]

Go for it if it floats your boat though!

Graham

Joerg

I think the idea is not to bad!
In a drawer of my workshop there are tree 5phase motors sleeping!!!!
So a universal interface could also awake some 2, 3, or even 5phase motors.
But i think it is worth to reflect the design! I think doing it with discrete parts will
create a lot of work. I would prefer creating a project with com integrated parts.

Saluti Joerg

PS. I'm studying a desing with some L298.

Philldapill

Joerg, unless I don't understand my own circuit, I'm not using them as comparators. In a way, they are like a voltage follower. The pot is used to adjust the current flowing by feeding the opamp a voltage, which it then compares to the voltage dropped across the shunt, and increases/decreases the output voltage in turn.

Joerg

Your right,
i was thinking of a choppered device! (d

Philldapill

I know what you mean about power dissipation being high. That was one of my concerns. If I understand this correctly, the main power transistors will be dropping the excess voltage when the coils of the motor are dropping no voltage. This in turn will lead to the transistors dropping a huge amount of power defined as the voltage drop across them times the current(which should be fairly constant). Because this is meant to be a universal controller, everything should be fairly dynamic. If this were used with a static motor, i.e. the same one being designed around, I Think I could match the motor to a particular capacitor, and use the capacitor to discharge a high voltage through the inductor. This way, the voltage and current would be 90 degrees out of phase, providing virtually no voltage drop.

lnielsen

I am also interested in motor controllers. I am currently using Bioloid AX-12+ servos for my robot project but the torque feedback is not very fast and it would be very difficult to limit the torque dynamically. I would love to see a propeller based servo like the OpenServo project. I would like to see the Propeller have direct control of the current. Maybe a variable torque servo with a spring-like function in the PID to help absorb joint impact. Most servos use DC motors but some use steppers or BLDC

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BioProp: Robotics - Powered by Bioloids and controlled by the Propeller

Philldapill

By the way, Joerg, I worked for a german company that dealt with a company called Systech. Do you guys have anything to do with conveyors of anykind?

Joerg

Hi Philldapill

NO! There are 1001 SYSTECH's in the word (i think i was some kind of stupid to choose this name 25 years ago!).
I have also registered the name for Switzerland, but it does not really protect the brand! (unless you spend a lot of $$$$!)

Saluti Joerg

Philldapill

So you are in business for yourself?

Joerg

Yes and No!

No: Until recently i have been teaching electronics and microprocessor stuff at a technical university. But since in Switzerland they changed the system the 50% job has been eliminated!
Yes: i am doing developments in electronics and m... stuff as well as i do some repairing jobs for obsolete things! (mechanics, pneumatics, hydraulic, .....) and i try to start a Project for renewable energy...

Saluti Joerg