understanding bipolar/uniploar

[freak_brain]

Hello Friends

I have motors that are 4.4V 1.5A bipolar. So exactly what does this mean, bipolar? The motors are 6 wire. Is bipolar using full winding or using the half winding leg?


Thanks
-Allen

[Mariss Freimanis]

Uniplolar means "single voltage", bipolar means "+/- voltage". These designations apply to drives, not the motor. Only unipolar (6-wire) motors work with unipolar drives. All motors (4, 6 and 8-wire) work with bipolar drives.

Step motors are AC motors. The current thru the motor most reverse direction in the winding for the motor to move. Unipolar and bipolar are drive schemes to make that happen. Below are examples of each (hope the ASCII art survives posting):

Mariss


Bipolar drive:

0V ---^^^^--- +V
<----- I


+V ---^^^^--- 0V
I----->


Unipolar drive:

+V|
<-----I |
0V ---^^^^--- open

+V

| I----->

open ---^^^^--- 0V

[bunalmis]

Bipolar and unipolar coils and activations.

[freak_brain]

Mariss,

I am using g201's with the motors I stated above. The motors are getting hot. This is leading me to believe I have something wrong. I have wired them using the full winding legs. Used a 12k resistor(I think, will confirm) on the gecko to set the amps and I have 71V at the drive from the power supply. Am I doing something wrong? What I am wondering is if I should be using the half winding leg?

Thanks
Allen

[ger21]

Do you really need the 71V? The higher the voltage you use, the hotter they'll get.

[freak_brain]

thanks for the help guys...love the animated picture bunamis.

-Allen

[freak_brain]

Well, I guess that is the question ger. I'm not sure. The gecko literature says between 4-20 times the motors rated voltage. Maybe I am pushing that rule a little to far? It's what I ended up with so I went with it. I can drop the voltage if that's the problem. Any suggestions would be great.

-Allen

[Chris D]

Originally Posted by freak_brain Mariss, I am using g201's with the motors I stated above. The motors are getting hot. Thanks Allen

Hi Allen,

I am no where near an expert on electronics and such, so I don't have an answer, rather a question. How hot is hot? That is a relative term and doesn't really say much when defining a problem. For instance, my steppers run around 120 degrees F. and the driver chips are around 135 Degrees F. Both seem really HOT to me, but, according to specs, the temps are within range.

Chris

[freak_brain]

Chris D....

I am not exactly sure of the temperature. They are hot to the touch, much hotter than others steppers I have had hooked up to these same drives and power supplies. I run them for 15-20 minutes and they are very hot to the touch. That is without any load too. Maybe this is acceptable, maybe not. I guess I need to take the egt off the racecar and check the temperature

-Allen

[ger21]

Like Chris says, most steppers are rated to 100°C, or 212°F. You'rs aren't that hot, are they??

I've heard that the best voltage to use, is the least voltage that will satisfy your performance requirements. Any more just adds extra heat.

[freak_brain]

Ger21,

Good rule to know. Maybe I will try cutting back the voltage and see what happens. Couldn't hurt anything that's for sure.

I don't think my motor are getting near the 212F (by the way, how do you make the degree symbol?)

off to work so I will check back tonight or maybe tomorrow morning. Thanks everyone, you guy are a great help.

-Allen

[CNCgr]

Originally Posted by freak_brain (by the way, how do you make the degree symbol?)

Alt + 0176 on the Num pad. (ok, I'm a nerd) ;°)