quick question

[cdngunner]

I am working with stepper motors at the moment and just wanted to know whether it was normal for them to get hot? (i assume so, but would like verification).

And yes it is running quite well, speeds up and slows down and all that.

 

[Technical]

Yes, quite normal.
The coils carry current most of the time (even when stationary) and so do generate a fair amount of heat.

 

[westaust55]

There are a few solutions to help stop the stepper motor getting hot.

1. If the required output torque is not great you can add a series resistor in the circuit with each winding.
I did this for one of my projects mainly to keep the current within the capability of the controller L293D chip. Only a few ohms were required.
Power = I^2 * R (= current * current x resistance)
so a reduction in current can have a significant reduction in power/heat but a incurs reduction in torque proportional to reduction in current.

2. Use a stepper controller chip that allows you to set the current limit for running and station (at position).
I have used the i2c controlled AMIS30622 chip which enables running and stopped current limits to be set.
This chip also has the advantage that you can operate at half, quarter, eighth or 16th stepping.
That gave me
- 16 * 200 = 3,200 steps per revolution using a standard 200 step per revolution stepper motor, and
- 16 * 48 = 768 steps with a 48 step/rev stepper motor.
There are some trade-offs such as a limit to how many steps in one direction but you can reset the current position to step 0 to continue from that previous point.
See my thread on the AMIS30622 chip here:
http://www.picaxeforum.co.uk/showthread.php?t=15071