[daddywoofdawg]

I have a design I'm working out in my head, and it involves a stepper motor,so I have a stepper motor question.can the motor be run with just a on/off forward/back manal switch,or does it need the controllers,power supply unit,etc.what is the very basic components to make a stepper motor go forward and reverse?

[handlewanker]

Hi.....a stepper motor relies on it's rotational movement by having 2 sets of windings in the field coils and sequentially/alternately powering each set with a single power pulse to make the motor armature turn one way or the other according to when which set is turned on and off etc.

This is something like a 3 phase motor that derives it's motion rotation from sequentially powering the windings from the mains power supply that arrives at your 3 phase wall socket as 3 wave forms that overlap each other by 120 degrees.

So, to power a single stepper motor you need a DC power supply of the right voltage and enough amps with a normal single stepper motor controller that supplies 2 phase DC current pulses that sequentially turn on and off, and then a computer and a program to tell the controller to do so.

You can get single stepper controllers on EBAY quite cheaply.

Somewhere in that equation I think you also need a program like Mach 3 to make sense of the computer output.......but this is as far as I know.

You "could" connect each coil set to a DC supply and briefly power each one on and off in a sequence manually which will make the armature move, but is not practical as the steps only move the armature 1/200th of a turn at each power pulse.

It's a bit more complicated than that explanation as the armature has to be held once the first directional pulse is appllied and before the next pulse on the other coil set is activated etc etc or the armature will just be erratically moved.

It's not just a simple connect to a DC supply and you have a motro, but I suspect that if you created a 2 phase supply from a single phase supply and DC rectified it, it "might" work.....just need more info on that score.

I believe...... but am not 100% sure...... that most DIY 3 phase rotary converters are actually 2 phase suppliers with the 3rd phase generated from capacitors, so you could investigate if this is a path for experiment, but it's mains voltage, so be careful.
Ian.

[daddywoofdawg]

ok so that thought may not work,what I need is a small motor,about the size of a stepper but doesn't have to be one,that can turn forward and reverse,with a strong torque,Ac or dc.any ideas?

[A_Camera]

ok so that thought may not work,what I need is a small motor,about the size of a stepper but doesn't have to be one,that can turn forward and reverse,with a strong torque,Ac or dc.any ideas?

Big stepper with high torque or small one with very little torque... all controlled the same way. You can't just use a switch, you need a motion controller providing quadrature modulated pulses and a driver stage which provides the necessary voltage/current for the motor size.

Describe your thoughts in more details. If you need exact positioning then it is complicated, but if you just want to spin forward and reverse then maybe a simple DC motor is the best solution. Why do you need a stepper?

[daddywoofdawg]

I just thought a stepper might work,I don't need a stepper just want some motor small in size to turn forward and back with torque,and though maybe a stepper was the answer.I wank to rotate a crank with a switch.

[A_Camera]

Try a simple DC motor. Depending on the needed torque, all can rotate forward/reverse by simply changing polarity. Ebay is full of those, some with gear boxes if you need very high torque and slow speed.

dc motor high torque | eBay

[handlewanker]

Hi....a DC geared motor is the answer........if the motor is initially running at 10,000 rpm at a voltage of 12 volts with a current draw of 1 amp that's a 12 Watt motor..........if you gear the motor down to get 100 rpm or whatever....do the sums....you increase the torque a huge amount.

EBAY has millions of DC motors in many configurations.......you just need to establish the voltage and amps, also the RPM needed.

Bear in mind the size of the gearbox output shaft as you will need to couple it to your device and that takes a coupling that has to withstand the torque.

You will also need a DC power supply and probably a pulse width modulated controller (PWM) if you want a variable speed output.

The DC power supply will most commonly be a switch mode or electronic device, as opposed to a transformer one, and that can be a cost factor to consider.......big transformers are costly and heavy and need further bridge rectifier and capacitor modifying to get a smoothed output and also a PWM too for the control.

If an electronic power supply fails....as they frequently do.....they are throw away.......transformer types are a bit more robust and usually fail in the diode and capacitor section.

You could work with a base of 12 volts and utilise an old PC power supply that has 12 volts and a large amperage, and would cost next to nothing.
Ian..

[daddywoofdawg]

Is there a easy way with common tools,to figure out how much torque it takes to rotate a shaft,so I can figure how what kind of torque I would need in a motor? I want to turn the shaft on a table saw miter wheel.the one that you turn to change the blade from 90 to 45?

[handlewanker]

Hi.....that's a difficult question.......if it was the saw shaft that is stationary and not cutting the amount of torque to make it rotate is miniscule, but if the shaft is the one that you rotate to make the saw itself tilt over to the required angle that's a different matter.

All things that rotate can be measured with a dynamometer type device.

That is, in principle..... if you clamp a foot (12") long lever to the shaft of the tilting mechanism to make it rotate and then add weights to the end of the lever to make it move........... every pound of weight, or part thereof, you add to the lever is called foot pounds of torque, or a measure of the amount of force that is required to make it rotate in pounds at a distance of 1 foot (12") from the centre of the shaft.

You can also use a spring balance instead of solid weights to measure the point where the lever overcomes the friction of the shaft and starts to rotate it.
Ian.

[handlewanker]

Hi again.....you could use a cordless screw driver to rotate the saw tilt spindle as it's already got forward and reverse with a chuck and only needs attaching to a bracket etc to get it in position......it has a clutch too so you can set it to prevent over running the tilt mechanism and burning the motor at the end of the travel.
Ian.

[Al_The_Man]

Yes you can use a simple spring scale and a pulley with a know dia and string around the shaft or pulley and measure the In-lb required to move the shaft.
If this is just a slow movement to move from point to point, a simple geared DC motor and a couple of limit switches and a DPDT centre off switch.
Al.