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Topic: Stepper getting very hot (Read 2509 times) previous topic - next topic

ZOR2

Has anyone worked with the bipolar stepper ST-PM35-16-11C

I tried using a L283D but the chip got very hot. So now I am trying to use the A4988 driver. The driver runs cool but the stepper gets very hot.

I am trying to run it slowly as a pan for a camera. I have the A4988 current pot set at minimum.

Is there a better way to drive the motor in small steps. I have MS1,MS2 and MS3 held high.

Thanks

Code: [Select]

/*     Simple Stepper Motor Control Exaple Code
*
*  by Dejan Nedelkovski, www.HowToMechatronics.com
*
*/
// defines pins numbers
const int stepPin = 3;
const int dirPin = 4;

void setup()
{
  // Sets the two pins as Outputs
  pinMode(stepPin, OUTPUT);
  pinMode(dirPin, OUTPUT);
}
void loop()
{
  digitalWrite(dirPin, HIGH); // Enables the motor to move in a particular direction
  // Makes 200 pulses for making one full cycle rotation
  for (int x = 0; x < 25; x++)
  {
    digitalWrite(stepPin, HIGH);
    delayMicroseconds(500);
    digitalWrite(stepPin, LOW);
    delayMicroseconds(500);
  }
  delay(1000); // One second delay
 
}



RayLivingston

Stepper motors DO get hot, because they run max power nearly all the time.  Some drivers will have an "idle" mode that reduces current when the motor is not actually moving, but the motor will still get hot, even if it's never moved.  Most stepper motors are rated for continuous operation at up toe 85C case temperature.

Regards,
Ray L.

ZOR2

Many thanks Ray, that answers that then. Fortunately being used for panning a camera, at least there will be off times when it can cool down. Just found the enable pin on the A4988 drive board. Have a good weekend, thanks again.

Robin2

An L298 is not a good choice for driving a stepper motor because it cannot limit the current to protect the motor. So either you use a too-low voltage for good performance or you risk damage to the motor.

You should use a specialized stepper driver.

That said, it is normal for stepper motors to be hot - uncomfortable to touch.

Post a link to the datasheet for your stepper motor.

...R
Stepper Motor Basics
Simple Stepper Code


Two or three hours spent thinking and reading documentation solves most programming problems.

lappa

I have a small ST- PM35-15-11C stepper which gets extremely hot. The specifications state 400mA current but the amps measured per coil are 2.4A. The specs. state 4 ohm per phase so you would expect approx. 3A from a 12v supply. When running from the Arduino via a L298 driver board, the average current is 2 plus amps.
Is this variation between the specification (400mA) and the actual value (2.5A) normal?

PaulMurrayCbr

#5
Feb 11, 2018, 10:00 am Last Edit: Feb 11, 2018, 10:01 am by PaulMurrayCbr
It depends on whether you need the stepper to "hold" while it is not moving. If you don't need this, then it can be turned off altogether - but this means that you can't rely on the steps being accurately tracked by the sketch.

- the stepper might be able to run on less current
- perhaps less current might be needed while it is holding position as opposed to moving

You might be able to rig up some sort of clutch to hold position - a spring loaded thing pulled back by a solenoid during panning. You'd want to ramp the solenoid current so that it doesn't shake the frame.

Or, add a couple of heatsinks to the steeper case and call it good.
http://paulmurraycbr.github.io/ArduinoTheOOWay.html

Robin2

#6
Feb 11, 2018, 10:02 am Last Edit: Feb 11, 2018, 10:02 am by Robin2
@lappa, you need to post a link to the datasheet for your stepper motor.

Have you carefully read all of the earlier advice in this Thread?

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

lappa

Yes I have Robin2. I do understand that steppers get hot.
My question was regarding stepper motor amps specs to actual amps measured and whether this was normal?
I measured each winding at 4.5ohms. Each coil individually connected to a 12V supply gave 2.4A which is close to Ohms Law calcs.
The measured running amps was done with the stepper rotating at 30 rpm, not at idle/hold.
The actual running current was total circuit current as measured at the 12v power supply

Data Sheet
https://cdn.sparkfun.com/datasheets/Robotics/ST-PM35-15-11C.pdf


Robin2

It's not surprising if a motor designed for 400mA gets very hot if you run 2400mA through its coils. It's amazing that it has not been destroyed.

That's why an L298 is not suitable. If you use a Pololu A4988 or DRV8825 you can adjust the max current to protect the motor.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

lappa

That was my thoughts also. I used that Stepper motor with a ML6500 and set up the current limiting and it seems O/K. It just seems strange that there is no note on the stepper spec sheet re use of a current controlled driver as it says it's a 12v stepper. With the L298 driver you would have to drop the voltage to something like 1.6V to limit the current to 400mA and i'm fairly sure it wouldn't drive.
I tried the L298 with this stepper as I saw it on a tutorial with a similar looking stepper - no stepper number was given so I don't have the specs.
My object is to drive Automotive Steppers in ISCs and EGRs (which I have no specs for) so I thought  the L298 with its 2A limit would be more suitable. I'll try both a L298 and an MP6500 tomorrow on an ISC and see how it goes.
Thanks for the reply.

Robin2

That was my thoughts also. I used that Stepper motor with a ML6500 and set up the current limiting and it seems O/K. It just seems strange that there is no note on the stepper spec sheet re use of a current controlled driver as it says it's a 12v stepper.
I have no idea why it says 12v. With 4 ohms and 0.4 amps the nominal voltage would be 1.6v. Have you measured the coild resistance with your multimeter?

Quote
so I thought  the L298 with its 2A limit would be more suitable.
It is wrong if you are thinking of the L298 as having a 2 amp cutoff that would protect things. The only limit the L298 has is an over-temperature shutdown and when that kicks in depends on how the device is cooled.

The current limitation in a specialized stepper motor driver is altogether more sophisticated as it checks the current many times during each stepper pulse.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

lappa

As soon as I noticed the stepper getting hot, I did a quick check of the current and switched off.  Stepper is still OK

Re the 4 ohms .4A, I calculated the same as you, 1.6V even though it states 12v.

Coil resistance in the spec. sheet is 4 ohms but when measured, one is 4.5 and the other is 4.6 ohms with meter lead resistance taken into account.

Guess I'll stick with the MP6500 at the moment until I find a better driver board.
Thanks

Robin2

Post a link to the datasheet for the MP6500.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

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