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Author Topic: Steppers for CNC  (Read 2758 times)
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Hi, i am wondering, if arduino UNO with 3 Easydrivers would work instead of http://www.buildyourcnc.com/item/electronicsAndMotors-parallel-breakout-relay and http://www.buildyourcnc.com/item/electronicsAndMotors-stepper-driver-3!0a. I want to build 3 axis CNC machine, and i see arduino as perfect, easy and cheap solution.
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To quote the EasyDriver site:
Quote
Quick Specs:
Each EasyDriver can drive up to about 750mA per phase of a bi-polar stepper motor.

If you want much more current than that you won't get away with using an A3967 (or any other
single chip driver without a heat slug).
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That was the information i needed smiley, so i won´t be able to connect steppers that require more than 750 mA. Are there any other drivers for arduino?
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See what I did with my project
http://www.thebox.myzen.co.uk/Hardware/CNC_Conversion.html
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i want something with bigger travel distance, something like this http://www.buildyourcnc.com/Documents/CNC%20Kit%201-1.pdf
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Looks like you will need something in the 5 to 15 amp drive range. There is a site called DIY CNC that has some good drivers. On my iPad otherwise I would search and post the link.
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The problem with driving 3A steppers is that there isn't really a single-chip driver that can
handle that current since integrated MOSFETs are DMOS (lateral current flow), not the more
efficient vertical current flow of discrete power MOSFETs.  DMOS devices go down to about
0.2 ohm minimum, whereas a driver using discrete MOSFETs can use devices with 0.002 ohms
of on-resistance.

There are some DMOS stepper driver chips in heat-slug packages, so these are the best
current handlers if on a big heatsink with a fan, able to dissipate many watts.
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What biggest travel distance would handle steppers that require less than 750mA?
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Travle distance is not the issue. The issue is one of speed and torque. As you lower the speed the torque goes up for a fixed ammount of current. So you need to know how much torque you need.
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I am new in this sectors of electronics... is there any equation or something like that to calculate torque?
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Not an equation as it depends on a lot of things inside the motor. The torque / current curve will be in the motor's data sheet.
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Can you recommend me any motor that Easydriver would handle and would fit in that machine i posted before?
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Have a look here:-
Quote
They have good data sheets with each motor, well as good as motor data sheets ever get.
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I have decided to make something small. It is my first machine like that, so i think that small start would be good. What motors would be good for machine that have travel distance 30x30 cm? (I don´t know z axis yet).
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As I said travel distance is not a factor the ones I used were  FL39T34-0654A and I also used them in a Rep Rap so they have quite a bit of kick.
Have a look at there page on motors
http://reprap.org/wiki/NEMA_Motor
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