## stepper motor problems

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
mikeb
Posts: 85
Joined: Fri Jul 12, 2002 1:01 am
Location: calif.
Contact:

### stepper motor problems

i have a unipolar stepper motor thats rated 5 volts 3.6 ohms, step angle 7.5 degrees 1.38 amps/phase, my questions is whether this is the maximum allow current that the coils can handle per step angle or is this the current that is required to make the motor rotate.the motor is from a surplus source but has never been used.
im trying to figure out the wiring to connect this motor, the motor has 6 wires an i have successfully figured out the 2 common wires an now im trying to figure out which is for the different coils. i have information as far as how to connect the motor to a volt souce by connecting both or either common wire then grounding 1 of the remaining four wires assuming that its connected to coil 4 then connecting each of the 3 remaining wires in turn an watchiung the results of the motor, whether its direction is clockwise indicating coil 3 or counter clock wise indicating coil 1, an no response from coil 2. after connecting the coils in this manner i get a response from the motor but it wont turn but the response seem to indicate the coils are not energized enough to turn the motor. but 2 wires respond by making a clicking noise while one does not so it appears that the wires are responding as the diagram has said. my question is whether the rating of the motor is its maximum rating, or is it the requiredcurrent an voltage to turn the motor. i connected the motor to a 12 volt source at 1.21 amps still with no respond other then it clicks like it wants to energize but it doesnt. if any one can help me with this id be most appreciative.

grant fair
Posts: 184
Joined: Sun Feb 23, 2003 1:01 am
Location: Toronto
Contact:

### Re: stepper motor problems

The rated current is the maximum current per phase that the stepper can handle without overheating and eventually destroying itself. Steppers can operate (with reduced torque) at reduced current levels. <p>It is possible to use a power resistor in series with a higher than rated voltage and thereby increase stepper torque. The important thing is to use Ohm's law to ensure that the resistor is the right value for the voltage used to provide the specified current. But you would not need to do this to test the motor.<p>I hope this helps; I am not sure what to make of the symptoms you describe but perhaps someone else on the list will be able to help you out.<p>Grant
Grant

Chris Foley
Posts: 146
Joined: Mon Jan 13, 2003 1:01 am
Location: Chicago IL
Contact:

### Re: stepper motor problems

You might want to look at one of the better stepper motor tutorials available on the web...<p>http://www.cs.uiowa.edu/~jones/step/<p>This will answer most of your questions.

Will
Posts: 310
Joined: Tue Feb 11, 2003 1:01 am
Location: Katy Texas
Contact:

### Re: stepper motor problems

Grant,
Satisfy my curiosity - Why would including a resistor increase the stepper torque ?
BB

grant fair
Posts: 184
Joined: Sun Feb 23, 2003 1:01 am
Location: Toronto
Contact:

### Re: stepper motor problems

Will -<p>It takes time after the power to a stepper coil is switched on to achieve a magnetic field in the coil. The time to achieve this is reduced with a higher voltage which is allowable with the current limiting resistor. It has to do with the inductance of the coil.<p>I'm not entirely clear on the reasons for this, so someone else may be able to add or clarify it. But I do know that I have been running steppers at voltages up to 30v from a current limiting supply I made (the current limiting is instead of the resistor) and subjectively, the torque is increased noticeably (the old grab the shaft and try to keep it from turning "measurement").<p>Grant
Grant

grant fair
Posts: 184
Joined: Sun Feb 23, 2003 1:01 am
Location: Toronto
Contact:

### Re: stepper motor problems

Will - the Jones site above explains it in more detail.<p>Grant
Grant

mikeb
Posts: 85
Joined: Fri Jul 12, 2002 1:01 am
Location: calif.
Contact:

### Re: stepper motor problems

HELLO GRANT ,WILL,CHRIS I WAS JUST STOPPING BY TO THANK ALL U GUYS FOR THE INFO U GAVE ME ON STEPPERS, THE JONES SITE WAS REALLY HELPFUL AS WELL. THE PROBLEM TURNED OUT TOP BE THAT I NEEDED TO APPLY POWER TO BOTH COMMON LEADS AT THE SAME TIME IN ORDER FOR THER MOTOR TO ROTATE. THE ARTCLE I WAS USING SAID ONLY ONE COMMON LEAD NEED TO BE CONNECTED ONCE AGAIN THANKS A BUNCH

### Who is online

Users browsing this forum: Google [Bot] and 50 guests