Using L293D with grbl for cnc ?

This was the image on grbl website:

How do I connect L293D to it? Is there a software mod required? Will it still support acceleration and microsteppping?

I don't think the L293 supports microstepping. You would need a microstep capable stepper driver like the RAMPS A4988.
http://www.ebay.com/itm/A4988-RAMPS-Pololu-StepStick-stepper-motor-driver-with-heatsink-Prusa-Mendel-/201084529309?ssPageName=ADME:L:OC:US:1120

The L293D is definitely not a Step & Direction stepper controller. It is not suitable for use in a grbl system unless you add a conversion from Step & Direction to bipolar phase shifting. If you add that to the grbl software then each of the three axes will need four pins instead of two. I don't think the UNO has enough spare pins for that. Typically people use three Step & Direction drivers from a company like Polulu.

For CNC you should not let your stepper controller have control of acceleration. Part of the CNC controller's job is to keep the motor positions synchronized so that the head travels in a straight line, even when running diagonally. If the controller did acceleration the diagonal lines would get warped.

Thanks for the replies.

I had a hard time finding such drivers online, from indian sites at nominal prices. Feel free to suggest one.

Is there a known way to use L293D with grbl?

We often think that goods from India cost less than here in the USA. it seems that the Poulou had distributors in India. alas, looking it seem Rs 1500 is about what they are asking ($26 USD) to 999 ($16 USD)

http://danuc.in/index.php?main_page=product_info&products_id=105 is asking Rs630

we here in the US use ebay and get the same device, with free shipping for half of that.

the problem with the L293 is that requires 4 signals. one for each step. you send them one way and the motor spins clockwise. you send the pulses the opposite and the motor spins counter clockwise.

what is most common in the CNC world is one pin that sends the pulse stream and a second pin that signals what direction the motor is to spin. this is known as step and direction.

second is microstepping. when moving a motor one step at a time, you have a lot of vibration under a certain speed. as the speed increases the momentum of the motor is more continuous and the motor moves in a much smoother fashion.

with the h-bridge, you can half step and that will immediately eliminate most of the vibration, but at low cost and without quality circuits, your motor power is double at a half step.

johnwasser:
For CNC you should not let your stepper controller have control of acceleration. Part of the CNC controller’s job is to keep the motor positions synchronized so that the head travels in a straight line, even when running diagonally. If the controller did acceleration the diagonal lines would get warped.

I disagree with you 100%

the ONLY place the acceleration should be in in the CONTROLLER.

the controller is the logic that will ramp up one axis, and match the other axes to the correct location.

the driver only disperses the power as directed by the controller.

… my head hurts when people call a driver a controller. it is like calling an UNO a shift register… up load the sketch to the shift register… then the shift register will signal the shift register… ahhhhhhhhh.,…

^
nice one XD XD

okay, so the software takes care of the acceleration and stuff and the only thing missing in L293D is microstepping, and the requirement for double the number of pins. right?

Well, I actually got my arduino uno for Rs 400 (its a freeduino actually). Both Poulou and EasyDriver are available at no less than Rs 600+shipping. Some are selling at Rs 1000+ a piece. Im building a 2-axis cnc machine (maybe a laser engraver), just as a part of my getting-bored-projects... Im gonna mod a printer directly, by putting another stepper in place of the dc motor.

I did find that theres a mod for grbl 0.7 to make it usable with hbridges. Home · grbl/grbl Wiki · GitHub
Can't figure out how to connect though.

Can’t figure out how to connect though.

see attached

stepper_circuit.png