I would say it's the motor, steppers aren't fast devices, but increasing the supply voltage helps a lot (try 48V instead of 24V, with suitable resistors of course).

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Thanks.Ok,i'll try it out.so in this case i will use a 300 ohm (5 to 10W) resistor for my Rx and Ry coil .I'll let u all know the result of this later.thanks guys!

 

How fast are you trying to get anyway?.

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the faster the better actually but our minimum requirement would be 1600 step/rev or 1140 rev/minute.for u all information currently i am using a microstepping driver to drive the motor but now i need to use a IC(UCN8048B) to subsitute the driver because it cost me so much. can i reach this speed if i use this driver?Thanks

 

1140 revs per minute sounds a lot higher than I would have thought?, steppers are only slow speed so I'm doubtful.

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1140 RPM (19 rot/sec) is doable if you have a motor willing to cooperate but you will have so little torque that the slightest load may stall it.

What is preventing you from using a speed controlled DC motor?

 

DC motor is fast but easy to spoil,so everytime the motor spoil i need to replace a new one,that's why i think of this stepper motor.is there any other way i can acheive 8 microstep/step if i use a bigger motor?and one thing is that if only DC motor itself there will not be any torque present.

 

DC motors are easy to spoil? A stepper motor is a DC motor so I'm not sure what you mean by that.

In terms of microstepping, you can use 8 microstep/step on any stepper motor. That does not mean that each microstep will be 1/8 of a normal step. Tolerances in the manufacturing process as well as the driver's waveform results in different step sizes when moving between full steps. While not uniform in size, their sum will total a full step for the motor. This has little to do with the size of the motor but more so its build quality. More expensive motors tend to have a more uniform microsteps.

What do you mean by "if only DC motor itself there will not be any torque present?" Fundamentally, a stepper motor has considerable holding torque which means it is very good at holding a stationary position. On the other hand their torque steadily reduces when their speed increases. Normal DC motors (even with a very good servo controller) have much less holding torque than a stepper. They do provide considerably more torque when rotating, especially at high speeds.

 

what i mean here is that when turning at high speed the DC motor will hv 0 torque and this will cause the DC motor to easily got spoiled.Another question is that for this UCN8048B is it neccessary for me to "ONLY" use 6 wire stepper motor?because when i try 4 wire or 8 wire stepper motor with this IC it wont work.Could anybody tell me what had happened?

 

You are incorrect about DC motors. They do make plenty of torque at high RPMs. Stepper motors make less torque the faster they are spun.

If you have an 8 wire stepper motor, you can make it behave like a 6 or 4 wire motor. There is no sense in writing everything twice so I suggest you read through this excellent stepper motor tutorial:

http://www.cs.uiowa.edu/~jones/step/

 

What is the maximum desired RPM, and how much torque do you need? I just finished tacking some pretty beefy steppers onto a milling machine, and they barely do 10rev/sec.

The three main types of DC motors are: DC brushed motors - cheapest, easiest to get, steppers - high torque at zero velocity, low-medium speed only, and DC brushless - most expensive and semi-custom, capable of very high power density and extremely high speeds.

As for stepper motor types - 5 or 6 wire ones are usually "unipolar" varieties. 4 wires are "bipolar" - they have higher performance than unipolar kinds, but require more complex drivers, and 8 wire'd ones are configurable to be either type. Keep in mind that the driver chip you've chosen can only drive unipolar steppers, or the 8 wire kind if you setup the coils properly.

James

 

thanks james,i think i configured the wire wrongly ,but how to make sure my configuration of the motor of 8 wire (Bifilar motors) correct as unipolar motor,because i need to use the 8 wire motor as unipolar motors,i got 8 wires coming out from the motor yellow ,orange,black,red,red stripe,black stripe,orange stripe and yellow stripe.how to connect this 8 wire for me to use it as unipolar motor?Thanks.

 

You should read section 1 of the link phalanx posted - it'll give you a general idea of how to do the testing, but it isn't going to be terribly easy... And going by colors is probably not useful at all.

First grab an ohmmeter and figure out how the wires are paired. Then the way I'd proceed (since I have a DC power supply handy, and don't feel like trying to setup an AC power supply) is to find turn each coil on and try to "match" them up. When you apply power to a particular coil, it'll cause the stepper to snap to a certain position. There should be another coil that causes it to snap to the same position - obviously you'll need to test and label the coils and *polarities* as you go along. Once you've identified everything, just wire up each pair of coils in series, and presto, 6 wires.

 

Thanks for the way to test out the polarities of the wiring,but wont all the stepper motor manufacture hv to follow the colour code for the wiring?would they have certain standard for this?Anyway i'll try out the method you just told me,this can this be told by just using an ohm meter and measure out the resistance of any pair of wires?

 

If you can find the particular manufacturer, they should have documentation on it, and chances that they'll keep a certain wiring color scheme among their line of products. In general, I doubt that there is a standard wiring code for something like this.

You'll need to figure out the polarity of the coils, as well as how they're matched up against each other. You won't be able to do this with a meter. At the very least, you'll need some current-limited DC power supply - a couple batteries might be enough to just test out each coil - but without knowing anything else, that's the best I can recommend.

James