Hello all.
I was wondering if somebody have time to help.
is there any way to protect stepper motors from ( if 1 going to break or lose steps or driver fail )
Because i planing to make project with 6 stepper motors Nema42 (Wanti motors from Chine) without encoders. All motors will run with same speed at same time.So can we make in arduino code something
or i need some hardware for this?Thank you
Without encoders there will be no means to check whether a motor has moved the required number of steps.
If you have selected motors with adequate torque for your project what are circumstances in which you think that a step might be missed?
...R
Hi Robin.Thanks for replay.
Actually i am more afraid how automaticly machine in future if 1 motor or driver going break.
Is there any idea how to make drivers to communicate. there is on Driver CON1 port for serial communication. Driver is Wantai DQ2722MA.
Manufacturer's page has nothing to suggest that the motor provides position feedback, so the only way to make sure it's actually moving is by attaching a sensor to it - the encoder as suggested before sounds like a great solution for this.
Ahmo:
Actually i am more afraid how automaticly machine in future if 1 motor or driver going break.
That seems an unlikely scenario (though possible, of course). If the consequences of failure are expensive then it would be worth the trouble to put detectors on the motors.
If you you need to detect the situation where a single step is missed then you will need an encoder with as many pulses per revolution as there are steps. And you need to be aware that accurately detecting all those pulses requires a considerable effort by the microprocessor - especially if there is a large number of steps and pulses per second. I suspect you will find that a 16MHz Arduino is not fast enough for 6 motors and 6 encoders.
If it would be sufficient to detect that a motor had failed to complete a revolution a much simpler detector could be used that just produces one pulse per revolution. This could be worth considering because it would show up a major failure of a motor or driver.
...R
I was thinking on my work and i have idea,maybe silly idea 
I will have in project big metal gear for each motor.So maybe i can make something with arduino lasers.
Set laser between gear gap and in arduino code put "if all lasers are on/of constantly" (with delay time) all motors running else all motors stop.What you think? ;D
And 1 relay, to switch power off.
So you basically want to build an optical encoder.
Should do the job. Buying an encoder off the shelf as suggested before will be more reliable, and probably be cheaper. I do suppose you do want your sensor to be at least as robust as the motors themselves.
In any way it is possible Thank you
What you thing about this encoder:
And in future i wish build small welding robot arm (5 axis).Do you know some tracking laser so i can use with arduino.
Can i use this:
https://www.ebay.com/itm/Laser-Sensor-Diffuse-Reflectance-Detector-Module-for-Arduino/112750912834?hash=item1a407a6542:g:28oAAOSwE9lZr2l7
or CMUcam5 :
Ahmo:
What you thing about this encoder:
It seems only to produce 100 pulses per revolution. I presume your stepper motor produces 200?
And in future i wish build small welding robot arm (5 axis).Do you know some tracking laser so i can use with arduino.
One thing at a time. Learn to walk before trying to run.
...R
I know but working on many projects and when i order something from China it take about month to receive item. 
So i need more then 200 P/R next is 360 P/R on Ebay.
Ahmo:
Simple. Don't buy from China. I don't. There are lots of suppliers that can provide stuff within 2 or 3 days.
So i need more then 200 P/R next is 360 P/R on Ebay.
First you need to decide exactly what you want to achieve - and you have not told us with sufficient precision.
It would help to go back to basics. Suppose that one of your stepper motors fails to move as expected, what are the consequences? IIRC you have not even told us what the motors are being used for,
...R
Thank you for guys for your time.
I am so busy this month.I tested with laser - receiver 1 motor and it was fine.
i will try rest later again.