[vukboban]

greetings !

I made exact copy of this driver board http://pminmo.com/3axis/3axis.htm
only changes I made are instead of IRLZ 44 mosfet I used IRFZ 44

I am using some small unipolar steppers-3.9 V,1.3 A ,12 V power supply and current limiters 5.6 ohm ,9W resistors.

Now everything works fine,but resistors seem to heat pretty much,I can not touch them!
mosfets are not heating at all,even without heat sinks

Is this normal for current limiters to heat so much or I did something wrong here?
Thanks

[jeffs555]

Yes it is normal for current limiting resistors to get very hot. With a 12v supply, those resistors will be dissipating nearly 11 watts which is all turned into heat. That is also higher than the power rating of the resistors. You generally want a safety margin for the resistors so you would want at least 15 watt resistors.

You could eliminate the resistors and all the heat by building the chopper board at the bottom of that page.

[tshatat]

the small unipolar steppers not muth with the driver try to change it with a small resistane stepper motor i have the same problem and i solvet