Arduino CNC

Hello guys!As the tittle says...I wanted to know how many stepper motors can you control with an arduino uno using uln2803 chip.Is it possible to control 4 stepper motors using 2 of these ICs

Hi, welcome to this forum.
I've never understood why so many ULN2003 driver modules, with just 7 darlington-arrays, are sold. The uln2803 has 8 and is indeed capable of driving 2 motors.

The steppers do of course need to be unipolar and have to draw less current as the 2803 can handle.

If you want to make a serious CNC machine I suspect it would be better to use bipolar motors and specialized stepper drivers.

Have a look at Stepper Motor Basics

I have three steppers on a small lathe easily controlled by an Uno. I am using Pololu A4988 stepper drivers.

...R

Thanks for the quick reply guys (first time here :grinning: ) Going back to my question I have 6 wire stepper motor(so unipolar and bipolar doesn't matter)Using the uln2803 IC how many pins on the arduino will be used? each IC can drive 2 motor.What I fear is that I'll use up all my pins on this ...so I need your help!

Thanks!

Robin2:
If you want to make a serious CNC machine I suspect it would be better to use bipolar motors and specialized stepper drivers.

Have a look at Stepper Motor Basics

I have three steppers on a small lathe easily controlled by an Uno. I am using Pololu A4988 stepper drivers.

...R

Thanks for the introduction.Pretty useful!!

FlyingCow:
Hello guys!As the tittle says...I wanted to know how many stepper motors can you control with an arduino uno using uln2803 chip.Is it possible to control 4 stepper motors using 2 of these ICs

you can, but your application, stepper motor driver selection is based on 3 things.
application, application and application.
using hte 2803, you have to use the motor nameplate voltage as maximum. that is all you can use or you will burn up the motor. then you are limited to the maximum rating of the 2803 for current.
as Robin2 points out the A4899 stepper driver is a great chip for use with the Arduino because it uses a 2 pin control, one for stepping and one for direction.
also the it is a chopper driver. what this means is that your motor needs, say 5 volts and 1.5 amps. watts is amps times volts, so your motor will handle 7.5 watts.
a crude way of describing a chopper is that, you can feed it from a power supply that can deliver 12 volts and 10 amp. the chopper circuit will deliver 7.5 watts to your motor. the differnce is that it will feed it that 7.5 watts much faster because it will feed it 12 volts, then chop the amps to deliver the 7.5 watts motor speed is proportional to voltage.

if you use a 12v power supply on a 5v motor, the A4988 chip will be able to run that motor over 2x speed of the ULN2803 chip a 5v.

MOTOR SELECTION :
you can buy the same motor in 12 volts, 5 volts and 2 volts.
if you use a 12v motor and feed it 12v with the A4988, it will run the same speed as the ULN2803
if you use a 5v motor and feed it 12v with the A4988, it will run 2.4 times faster
if you use a 2v motor, it will run 6 times faster

the key is the RATIO of motor nameplate voltage to power supply voltage.

lower voltage motors are harder to find and cost a bit more, but deliver both more power and more speed.

dave-in-nj:
you can, but your application, stepper motor driver selection is based on 3 things.
application, application and application.
using hte 2803, you have to use the motor nameplate voltage as maximum. that is all you can use or you will burn up the motor. then you are limited to the maximum rating of the 2803 for current.
as Robin2 points out the A4899 stepper driver is a great chip for use with the Arduino because it uses a 2 pin control, one for stepping and one for direction.
also the it is a chopper driver. what this means is that your motor needs, say 5 volts and 1.5 amps. watts is amps times volts, so your motor will handle 7.5 watts.
a crude way of describing a chopper is that, you can feed it from a power supply that can deliver 12 volts and 10 amp. the chopper circuit will deliver 7.5 watts to your motor. the differnce is that it will feed it that 7.5 watts much faster because it will feed it 12 volts, then chop the amps to deliver the 7.5 watts motor speed is proportional to voltage.

if you use a 12v power supply on a 5v motor, the A4988 chip will be able to run that motor over 2x speed of the ULN2803 chip a 5v.

MOTOR SELECTION :
you can buy the same motor in 12 volts, 5 volts and 2 volts.
if you use a 12v motor and feed it 12v with the A4988, it will run the same speed as the ULN2803
if you use a 5v motor and feed it 12v with the A4988, it will run 2.4 times faster
if you use a 2v motor, it will run 6 times faster

the key is the RATIO of motor nameplate voltage to power supply voltage.

lower voltage motors are harder to find and cost a bit more, but deliver both more power and more speed.

Thanks for the reply!I have 4 5/12V stepper motors so the motors shouldn't be the problem but using the uln2803 will use up 4 pins on my arduino per motor(am I right here?)

FlyingCow:
Thanks for the reply!I have 4 5/12V stepper motors so the motors shouldn't be the problem but using the uln2803 will use up 4 pins on my arduino per motor(am I right here?)

If you have motors that can be used in bipolar mode then specialized stepper drivers that just take step and direction signals will save a lot of pins and ALSO greatly reduce the computational load on the Arduino.

...R