Stepper motor vibrate instead of turning?

[mesamune80]

Hi guys,need your help again here,as topic after finish all the connection of microcontroller and stepper motor with driver ,when i start the motor it appears to be vibrates instead of turning?What are the possibility of this kind of phenomena to happened?Thanks.

 

[Nigel Goodwin]

Wrong sequence.
Too much load.
Trying to step too quickly.
Too little drive current.

 

[bibinjohn]

see the delay time b/w two sequence also

Bibin John
www.booksbybibin.tk

 

[philba]

slow the whole thing down to a couple of steps per second. if it still vibrates then hook up leds to the control signals and see what you are telling it. spend a little time thinking through what you are doing...

 

[Papabravo]

Houston, we have found resonance!

 

[mesamune80]

Thanks guy,i found the problem at last!!

 

[philba]

gee the suspense is killing me. care to elaborate?

 

[mesamune80]

Ok,i'll make it clear to everyone,actually is a careless mistake (Hard to detect >_<).Why i said hard to detct here is because the solder of one output of the driver is touch to the next pin which is ground =.=" the touching cannot be seen if u don use magnifier class!! i just simply make them untouch then the problem solved!!! ^^

 

[mesamune80]

Ya one more thing is i just visited the allegro website and read the FAQs session for this A3977 microstepping driver got this as the external component:

The following components are required for correct operation of the A3977:

1) Rsense1 and Rsense2 - The external sense resistors required for the

PWM current control circuit. These should be noninductive type resistors.

Recommended maximum Rs value can be calculated using Rs = 0.5 / Itripmax.

Using a reasonably smaller value for Rs will dissipate less power in Rs

and provide headroom. There also needs to be a 0.1 µF mono/ceramic

capacitor in parallel with each of these resistors.
2) A 0.22 µF mono/ceramic capacitor must be placed between the CP1 and

CP2 pins.
3) The VREG pin should be decoupled with a 0.22 µF capacitor to ground.
4) Logic supply decoupling capacitor. A 0.1 µF ceramic capacitor is

recommended.
5) Decoupling capacitor - load supply. A value of > 47 µF electrolytic

capacitor is recommended. In addition, a 0.1 µF ceramic capacitor should

be placed in parallel, if high frequency issues are a concern.
6) A 0.1 µF capacitor is required on the PFD (Percent Fast Decay) pin.

from above could some one please explain to me what is this Itripmax? because i need to know waht value of resistor i need to use for my driver.Thanks ^_^

 

[philba]

You mean 3977, I think.

If I recall correctly, Itripmax is the current at which you want to turn off the coil drivers. i.e. max current your steppers should draw. When I designed an a3977 board, I used .2 for Rs with the expectation that I wouldn't drive any stepper coil over 2.5A.

by the way, they call it PWM but I don't think it is since the current rise in the coils is sensed via Rs and when the coil current reaches the trip current, it turns off the drivers. then it waits for a fixed time, turns on the drivers and repeats the process. it sort of looks like PWM but you don't control the duty cycle directly.

 

[mesamune80]

As the stepper motor i would be using are those high torque stepper motor ,for the current rating is 3A per phase
so i think for Rs i can use 0.2 and see the result whether the torque is enough or not,if not then lower Rs to achive my desired torque ^^

 

[philba]

Uh, you should spend a little more time in the datasheet. absolute max current is 2.5A. I wouldn't recommend running a 2.5 for very long.

Rs doesn't define torque, it is just used to sense current. the ref pin (14 on the plcc) defines the current trigger point. For a crude (but effective) control, use a trimmer to define a ref voltage.

also, people were seeing a lot of failures running at 35V so most people that make controllers based on the A3977 began spec'ing a 30V max.

 

[mesamune80]

i see, because the ic max output current is 2.5A i should give some tolerance here,i'll start with lower current 1st since my motor can stand up to 3A and i would like it to be ON for a long long hours,my motor would be operate for production!so long hours is one of the requirement.And the motor i would be driving is like this one here:**broken link removed**
Any suggestion would be appreciated.Thanks

 

[gaurav_chopra1985]

hi

as we know for stepper motor properly work we have to give electronics pulses to microcontroller and that pulses then given to the driver circuit for microcontroller . and used a sufficent driver circuit for microcontroller every controller need different type of driver circuit. as 89c51 need uln dr5iver. i had done this project.

 

[philba]

An atmel 51 + uln driver for that motor would never drive that motor well at all. even with current limiting resistors, it won't come close. I'm not even sure the A3977 will handle it, even in current limited chopper mode. it certainly won't generate full torque.

 

[mesamune80]

i am using pic16F877 + a motor driver to drive my motor, and i need high torque for that.holding torque ~1200mNm

 

[markcomp77]

Uh, you should spend a little more time in the datasheet. absolute max current is 2.5A. I wouldn't recommend running a 2.5 for very long.

I use 3A... and 2.8A (in CNC)
current sens = 0.16R
33-34V with over voltage protection (! important !)
**broken link removed**

I' traing my driver with 3,3A too
**broken link removed**

project/PCB...
https://www.cnc.info.pl/viewtopic.php?t=1783
**broken link removed**

 

[philba]

I wish you luck but don't be surpised if you smoke the chip at that voltage and current draw. keep en eye on the heat.

 

[markcomp77]

I wish you luck but don't be surpised if you smoke the chip at that voltage and current draw. keep en eye on the heat.

big radiator solving problem of heating... (and fan)
**broken link removed**

 

[philba]

forced air will certainly help. I'm glad you are happy with it. Just watch out for high speed stalls, you are running the chip over spec.