Stepper motor and controllers

[More Coffee]

I'm flirting with the idea of putting a power cross feed on my 9x20 bench lathe.
I think a stepper motor would offer more fluid control of the cutting tool.In the end for finer control, the motor will be run at a 4:1 ratio to the cross slide wheel
I would like to put together a system that's variable speed, forward/reverse with a normally off switch.
no microcontrollers or computer interface.. analog manual control through a switch and potentiometer only
So im doing a little research.. Nema 17 motor.
I'm looking at a motor that's rated at 5.32 Kg holding torque and operates 12v..

Does a stepper motor's holding torque represent its shaft torque.
Any recommendations for a simple circuit? Or an avaliable control and power supply?
Everything Im finding requires an interface with some other gadget.

Thanks for listening.

 

[3v0]

Think of holding torque as the max torque that can be externally applied to the shaft and have the stepper maintain the correct position.

The requirements of reversible and variable speed stepping more or less rule out the circuit being simple.
As long as you are going that far you may as well add a digital readout if it would be useful in your work.

I suggest you ask this question over on CNCZone.com

 

[More Coffee]

Hi.
Thanks for the response..
LOL..I thought the electrics was going to be the "simple" part.
The DRO..yes .I was going to modify a digital venier caliper for that..

Thanks again.

 

[Boncuk]

Hi,

considering what you can do and what you can spoil with a lathe I think a controller circuit will be a MUST for your project.

With a controller circuit you can vary stepping, select full wave, half wave and microstepping depending on the work you have to to. (Making a conical shape using full step operation the cone won't really be a cone.)

There are controller circuits having been designed for stand alone operation, hence you don't have to care for a microcontroller. It's all built into the chip.

I do not suggest to use bipolar stepper motors (2 coils with four wire connection) as the one you are planning. There are equivalent unipolar stepper motors with the same torque and speed parameters as that one.

The disadvantage of a bipolar stepper motor is the fact that you need two full H-bridges to control motor rotating direction, meaning eight power transistors wired logically to prevent shorts between upper and lower branch of the motor supply voltage with the supply voltage being reversed on the coils for reverse rotation.

A unipolar stepper motor has five to six wires with 4 coils (2X2 coils in series with a center tap wired to the positive branch of motor power supply) and changing direction is done via the logical sequence of controlling four power transistors without the probability of shorts.

Finally the holding torque is not the decisive criteria for your project. The tool support moves via a worm drive which can only be moved by the driving axle, no matter how tough the workpiece might be.

Boncuk

 

[Mr RB]

Any typical stepper motor driver will accept step pulses to move the motor and a direction pin to set motor direction.

You can use a 555 timer to generate the step pulses to adjust motor speed, and a toggle switch to set motor direction.

If you are willing to work with a microcontroller, the Linistepper stepper motor driver;
**broken link removed**



It comes with a PIC 16F628A that controls the stepper motor, so on the one simple driver PCB you can program it to do exact xtal-locked speeds under your control. It also has benefits of smoothness etc that comes from linear microstepping and is a perfect size for driving your size17 motor.

 

[ronv]

I didn't look at the current for your motor choice, but you might look at the L297 and L298. they are old but easy to use.