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Topic: Stepper motor heat (Read 1 time) previous topic - next topic



I just started my CNC research and tested the EasyDriver stepper driver. Now
I just wondered that after a few minutes of testing code, the drivers, steppers
and the 12V power supply gets very hot. I just wanted to confirm that this is
normal or if there are any issues with my setup. I dont want to burn down my house
if I forget to turn my steppers off...  :smiley-sweat:

Only two steppers are powered currently.

I measured:
- Steppers: approx. 45°C (113F°) (NEMA17, 0.33A, 2 phases) http://www.sparkfun.com/datasheets/Robotics/SM-42BYG011-25.pdf
- Drivers: approx. 55°C (131°F) (EasyDrivers)
- Power supply: approx 75°C (167°F) (12V, 800mA)

They are turning well, so I think the wiring is fine. Just want to confirm that
the heat is normal.

Thanks for your time!!


Each stepper motor is 0.33A, there are 3 steppers, if you drive them in wave mode (single phase at a time) you are overloading your supply by 25%, if in full step mode then you are overloading the supply by 150%.  So yes it's not surprising its running hot and you shouldn't be doing this...

If you want a supply that can drive them full-stepped or half-stepped rather than wave-mode you'll need a minimum of 2A from the supply.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]


Feb 17, 2012, 11:57 pm Last Edit: Feb 18, 2012, 12:09 am by asuryan Reason: 1
Thanks for your reply!

Well I expected something like that. :(
But I powered only two of them. The third one isnt connected yet.

Currently I run the drivers/steppers in 1/8 microstepping mode. So 200 -> 1600 steps
per revolution.

1. Does that mean that the "stepping mode" (1/1,1/2,1/4,1/8) influences the energy they
draw? How to calculate that?
2. What do you excatly mean by "wave mode"?
3. The steppers are energized one after another in my code so I thought that each coil
is only energized at a time. But yes you are right that would be 990mA for only the
steppers if they are powered the same time. In 1/8 microstepping mode would a power
supply of 1.5A be sufficient? Or do I have to calculate 0.33A x 2 per stepper -> 1.98A?
4. Does microstepping influence the holding torque?

To get around the power supply issue I would buy a new one:

Even if you dont speak german -> Its rated: 2250mA, 12V. Would that be sufficient?

My test code:
Code: [Select]

int motorDirPin = 9;
int motorXPin = 12;
int motorYPin = 11;
int motorZPin =10;
long u = 0;
int stepTime = 0;

LiquidCrystal lcd(7, 6, 5, 4, 3, 2);

void setup() {                
 lcd.begin(16, 2);
 pinMode(motorDirPin, OUTPUT);    
 pinMode(motorXPin, OUTPUT);
 pinMode(motorYPin, OUTPUT);
 pinMode(motorZPin, OUTPUT);
 digitalWrite(motorDirPin, LOW);
 digitalWrite(motorXPin, LOW);
 digitalWrite(motorYPin, LOW);
 digitalWrite(motorZPin, LOW);

void loop() {
 stepTime = millis();
 for(int i=0;i<1600;i++){
     digitalWrite(motorDirPin, HIGH);
     digitalWrite(motorXPin, HIGH);
     digitalWrite(motorDirPin, HIGH);
     digitalWrite(motorZPin, HIGH);
     digitalWrite(motorXPin, LOW);
     digitalWrite(motorZPin, LOW);
 stepTime = millis()-stepTime;
 lcd.setCursor(0, 0);
   lcd.setCursor(0, 1);
   lcd.print("Turnspeed ");


Microstepping modes switch on two windings at once.  Not both at 100%, but it'll still be more current than wave-mode  (|sin x|+|cos x| >= 1).  Crude half-stepping does power on two windings 100% at once though.  You might be OK with just two motors.  Measure the current if you can to check.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]


Feb 18, 2012, 11:46 am Last Edit: Feb 18, 2012, 12:12 pm by asuryan Reason: 1
Thank you!

I measured for the stepper circuit (the values oscillate a bit):
- > 1 stepper and driver powered: max. 400mA
- > 2 steppers and 2 drivers powered: max. 1000mA

Well so with 2 steppers Im overloading the powersupply as you mentioned
by approx. 25%... :( Guess I have to get a higher rated power supply (2250mA what
I mentioned above).

What I do not understand is that the value does not double when I power 2
identical devices. The amperes rising by 150%.

Just for information: what kind of temperatures is normal for driver chip, stepper
and powersupply when running?

Anyway: thanks for your time! :)


Commercial specification temperature range is < 85C, which is about 185F if my math is right.
However, the data sheet for various components may show de-rating charts -- lifetime, or capacity, or power handling, may go down with X amount per Y degrees over trigger point T. What these are typically varies by component -- there's no "one true way" (except keeping everything at 25 C, the nominal point, which isn't very realistic)
Get the data sheets for your components, and check!


Hi all! I just started my first Arduino project, almost same configuration of asuryan:

-1 stepper:  Mercury motor 2 phases, 12V, 0,33A (http://iprototype.be/products/robotics/servo-motors/stepper-motor)
- easy driver v4.4  (http://schmalzhaus.com/EasyDriver/)
- Power supply: (12V, 1A) (I had only this, taken from my internet router)

This is my wiring:

Before connecting the power, I tried to move the motor shaft and the power led lights up so I thought that connections were good.
After this I connected the power but I made a mistake, I connected it to the 5v output (stupid me) of the driver. When I figured out, I removed the power, but actually if I move the shaft the power led of the driver is not more lighting up.
Connecting the power and uploading the sketch in arduino the motor doesn't move, doesn't buzz, no reaction.
Now I'm trying to figure out if I burned the driver or the motor or simply my connections are not correct. I don't have any tester (sob).

Please help!
Thank you,


Any test that lit LEDs before powering the board were probably of little value, unless the documentation suggested that.

Hooking power backwards to the board? not having a schematic, it would probably be safe to say that something on the board failed. Do you have a schematic?


You mean the schematic of the driver? You can find it here: http://schmalzhaus.com/EasyDriver/EasyDriver_v44/EasyDriver_v44_sch.pdf. And this http://schmalzhaus.com/EasyDriver/EasyDriver_v44/EasyDriver_v44_brd.pdf and this http://www.fut-electronics.com/wp-content/uploads/2012/02/EasyDriver_V44_Description.jpg are pictures of the board.
My error was to connect 12V to the output. Can this damage the board? And also, not having a tester, I've connected the power inverted for a while. The motor never became warm so I think it cannot be damaged.


The motor is unlikely to die from its rated voltage, because it's designed to run both ways. That's in fact what the driver does, when it works right --
However, the driver board likely could. Most boards will be somewhat insulated against back EMI, but a prolonged period of bad voltage can burn out various components or the driver IC itself.
Also: You really should go to the local hobby store and buy a multimeter. A $5 Chinese piece of plastic with a gauge is a lot better than driving blind!
And when I say $5, do I really mean it? Yes! http://www.dealextreme.com/p/mf-110a-mini-handheld-multimeter-80491?item=12

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