[Arshia]

hi every1, i am using stepper motor for my cnc machine...its model no is em284 stp-42d221-01 by shinani kenshi......i dont know any specs of this motor neither voltage rating nor current rating even i dont know its RPM.i am usig IRF640 mosfets to drive stepper motor along with 817b optocoupler.
i am running my stepper motor at 12 V.i have to do diagonal motion so i am running two stepper motor simultaneously.
Problem is when i use 12 V power supply with 4.2 A current rating my motors are getting heatup and also driver circuit is also getting heat up....bt the motors are running smoothly and are not missing the steps.
and when i use 12 v supply with 2 A current rating both motors are missing the steps but this time both driver and motor are not getting hot.

I dont know where is the problem????what should i do??? either there is a problem in my driving voltage or problem in driving current or is there any other issue???

the driver circuit for both motors are in parallel that means if i use 2A source then 1A current is going in each driver means in motor.

Please help me out!!!!!

[jpascher]

Just using a rahther poor Driving circuit with "IRF640 mosfets to drive stepper motor along with 817b optocoupler" is not realy recomendabel.
What is the actual circuit you ar using?

[James Newton]

As jpascher says, that isn't a great way to drive a motor. A better driver, such as the open source THB6064AH kit I sell, would reduce motor heat.

Having said that, it's amazing how much heat you can remove from a motor with a little CPU cooler and some thermal paste. Clamp it on the side if the motor is square, and on the back if it's round. Cut a hole in the cooler if the motor shaft comes out.

[jpascher]

@James Newton
You do have a nice website!
I dont think it should be posted here, may some admin moveds it to a other thread later on after you answerd.
On a table on Your Website Stepper Motor Connection Options you write:
"not really an option, but you can just use the A coil and leave B disconnected to fake it with one coil. Not half coil, but half the coils."
Better chang this: to "it is an option, you can just use the half A coil and half B coil. Actually it is not half the coils, in reality it ragter is half the windings on A and B coil becaus A and B coil sit on one commen ion part."
Or so:
"Only one A coil and one B coil are connected. A+,A, B+,B' to bipolar driver (A-, B-, are held apart, disconnected from everything)

You should correct this becaus it is an option if higer speeds more touque with less power voltage is needed. And if you dissasemble a motor you will see that the windigs are not a problem if only half the windings on the coils are used. All is still symetrical your simlpcized drowings (pictures) with for coils gives the wrong impression.

So back to this thread depending on the motor type chanig wirering may also be an option. In this case using a better driving circuit is actualy the first to do.
Best regards. Johann

[James Newton]

Thanks Johann, I've updated that page, as suggested.

[jpascher]

Thanks James,
i did change the text in may privias comment here. And pleas do have a look at it again the text used now on your website is not correct.
My be you use the following line:
"Only one A coil and one B coil are connected. A+,A, B+,B' to bipolar driver (A-, B-, are held apart, disconnected from everything)

[James Newton]

Ah. Ok, I see. I've changed it to that.