Need Simple Push Button Controller

[edo]

I'm trying to find schematics/plans for a simple one motor controller than I don't need to connect to a computer to control. I have a Vexta 6V, 1.2A, .9 deg/step motor and I want to use a momentary contact rocker switch that will turn the motor about 90 degrees CW when I push it one way and CCW when I push it the other way. Any and all suggestions would be appreciated. Thanks.

[Al_The_Man]

Probabally could be done with any step/dir. drive amplifier.
The circuit to drive it using a 555 pulse generator with a Push-Button to a flip-flop to start it.
The output of the 555 to a decade ripple counter like a 7490 or similar with a carry out to a 5 pulse ripple counter, the output would be 50 pulses (90°)
the 5th pulse out to reset the flip-flop stopping the 555.
Direction could be done several ways or simply by a direction switch.
Al.

[kreutz]

Originally Posted by edo I'm trying to find schematics/plans for a simple one motor controller than I don't need to connect to a computer to control. I have a Vexta 6V, 1.2A, .9 deg/step motor and I want to use a momentary contact rocker switch that will turn the motor about 90 degrees CW when I push it one way and CCW when I push it the other way. Any and all suggestions would be appreciated. Thanks.

Any specs on speed or speed adjustment?, do you need precise positioning (microsteping)? Unipolar or bipolar motor?

[James Newton]

I think edo is looking for a way to demonstrate (or demonstrate his knowledge of) how steppers work. Think classroom. He will correct me if I'm wrong.

So what needs to be used is a set of momentary switches or a rotary switch that wires the battery to the coils in such a way that when the switches are pressed in order, or the rotary is turned, it causes the stepper to step.

Referring to the animation at:
http://techref.massmind.org/techref/io/steppers.htm the "a" and "b" lines are both grounded, and the remaining wires are connected to the hot in sequence. A rotary switch would seem to me to make the most sense. Just wire it up so that each coil is energized in turn. For the half step example, an 8 position switch would be required.

[edo]

To answer the questions, this is for a project at home and the only one getting educated would be me. I assume the motors are bipolar. I don't need precision, but would like repeatability, i.e, the same amount of movement +/- .1" each time I push a button. I'm not sure of the exact speed I need, but I'm estimating somewhere between 90-120 degrees in one second. I'll need to prototype this to determine the exact speed, distance, and torque needed, but have to start somewhere. See below for the gory details.

Details: I'm adding CNC control to my wife's quilting frame. I built a JGRO and the HobbyCNC controller board and am cutting parts to modify her machine. I'll eventually add steppers to the sewing machine carriage for X & Y motion, but before I do that, I have to automate the take up roller. If your not familar with quilting frames, they're 10' long tables with three rollers in front, one each for the quilt top, the batten (stuff in the middle), and the backing. These get put together and are attached to a take up roller. This roller extends the length of the frame and lays in the throat of the sewing machine. The sewing machine is on tracked rollers that allow it to be moved in an X and Y direction. You turn the machine on and can sew any design for a depth of about 7" along the entire 10' length of the quilt. The size of the sewing machine's throat limits the amount of Y travel. (See pics. The 2nd pic is a closeup of the sewing machine on the carriage with the take up roll in the machine's throat.)
I want to give her the capability to push a button mounted to the carriage to move the roller forward of backward as she gets close to the limits of the sewing machine. I've fabricated extension holders for each end of the takeup roller with a slot that lets the roller move 7". I have a 2.25" diameter gear attached to the end of the roller that sits in a rack. As the gear turns it moves the roller laterally. The 7" circumference will take the roll from one end of the slot to the other in about one revolution. A single push of a button should turn the gear enough to move it about 1/4 to 1/3 the distance (90-120 degrees) and will need to happen in about 1 second. I'll have to get it up and running to determine the ideal distance and time so whatever circuit I use will need to be adjustable. The adjustment can be with discrete components, e.g., different resistor and/or capacitor values, as when I get the right speed it won't need to be changed.

[James Newton]

Oh, sorry, my mistake.

For your application, how about a low cost gear motor with a cam and limit switches at both ends of the desired run? That would allow you to wire up the control switch, limit switches, and not need any other components.

[Al_The_Man]

For that accuracy and speed and flexibility, I still think the practical way would be to use either a step direction amplifier in conjunction with say logic circuitry.
You could also use discrete amplifiers and drive it direct similar to the switch method.
http://cnczone.com/forums/showthread.php?t=31194
Or use an off the shelf stepper drive, you could add sophistication in the way of programming by thumbwheel switch setting for the amount of steps.
Logic iC's are a few cents each.
And either way, you will need a power supply.
If you really wanted to get ambititious, It would be a good introduction to MicroChip PIC programming. They have app. notes for steppers etc.
Al.

[edo]

Good idea James - that would certainly be easier (and cheaper) if I could source the right size motor somewhere. Any ideas? One that runs at 20 RPM would be about right. I suspect I could do some minor adjustments to the speed by over or under powering it.

Having just built my CNC router, I thought it'd be cool to use a stepper. I was going to use a lead screw to push and pull the roller, which is why I put the gear and rack into the plan, but I did the math and figured I'd need a motor/lead screw combo to give me 150ipm.

[edo]

OK, Al, you got me while I was responding to James and put me back on track to using a stepper. Sorry James, but although a geared DC motor would be easier to implement, who knows how many I'd have to buy to get a prototype working at the right speed.

I'm capable of building boards and putting different circuits together, but I wouldn't know where to start putting something together from scratch. I found some 555 circuits but need some help with the components for the logic and amplifiers. I also wouldn't have a clue as to how to handle 1.2Amps through the circuit. I'm not asking you to design this for me, but a few pointers to existing circuits would help. Thanks again.

[Al_The_Man]

I will see what I can dig up in the next couple of days.
Al.

[student1616]

i think this what ur looking for http://www.imagesco.com/articles/picstepper/04.html
we were discussing abt its current capacity in the above thread.
i hope this will help u

[edo]

Thanks, Al - I'd appreciate seeing anything you come up with.

Student - I'd prefer to stay with discrete components and avoid a PIC solution if possible, but I'll check the circuits and discussion to see if I can learn more about current handling. Thanks.