Stepper (1204) temperature increase

I just purchased a small stepper and motor controller I adjusted the current for 420ma (70% of the 600ma rated value during full step mode). Running this from a regulated 5V supply.

Everything works fine as far as controlling the motor. My main concern at this point is the rather alarming temperature increase of the motor itself. In just a few minutes the motor becomes hot but not so hot as to be unable to hold it.

So I fully expect a temperature increase in that the motor is consuming at least 4 watts (25.00.420). That is not an inconsiderable amount in such a small motor.

My questions:

  1. Do these motors indeed run very warm or even hot? (Solved)
  2. Is there any published max temperature operating point for this motor? Not only do I have self heating, but I will have solar loading as well. (Solved)
  3. Do you have any experience in heat sinking the motor? Would IC heat sinks bonded to the outside of the motor help? How about a custom heat sink as part of the motor mount bracket? Would lowering the temperature increase the life span, or torque? (solved)

PS: I just found the temperature data in the datasheet (what a silly place to put it :wink: ). Looks like a 80C (176F) increase is expected with the environment from -20 to 50C (-4 to 122F). If I understand this right, the motor could get as hot as 122+176F or 198F! I should be well under that even with solar loading.

PSS: I ran a test over the weekend and the temperature increased from 67F to 130F. This appears to be well within the temerature limits.

Skye Sweeney

Yes, thermally bonded heat sinks will help cool the motor. RC car enthusiasts have some pretty neat-looking anodized aluminum heat sinks in various shapes that wrap around inrunner brushless motors (cylindrical) for example.
The main problem you’re going to run into is that the thermal conductivity between the coils and the motor housing isn’t that great. I e, even if you could pour liquid nitrogen onto the housing, the coils are snug and insulated on the inside, and thus would still get too warm if you drove them too hard.
Sounds like you’re not actually driving anything beyond spec, though, so the only other thing to worry about is the mounting of the motor – if that acts as insulator, you will get more heat build-up.

Hello, Skye.

I am glad you were able to find the information in the datasheet. Your conclusion about the temperature tolerances seems reasonable, though, your math on the temperature is a little off. You converted both of the temperature specifications in the datasheet to F before adding them to get the final temperature, but I would recommend adding them in units of C and then converting. This gives you a maximum temperature of 266 degrees F. (Also, 122 + 176 = 298 not 198.) If you do convert the specifications first you should not add in the extra 32 that comes from the equation F = 9/5 * C + 32 when converting the 80 degree C temperature rise, since it is a change in temperature, not an absolute temperature.

As for heat sinking, jwatte seems to have that covered pretty well. Adding cooling to your system might help increase the lifespan of the motor, but we do not have that characterized.

By the way, when calculating power consumption there will also be losses from the sense resistors and the FETs on the driver, but those losses should be small.

- Grant

Thanks for all the information. I think the basic motor temperature appears normal (although a bit surprising). My only concern is solar loading, but I think I can build a reflector and still keep the motor in free air. Will look to the RC community for possible heat sinks.