I have a hobby CNC machine running with three cd drive stepper motors in it using a 2amp supply for all of them, it is run by Arduino uno and EasyDrivers. Suddenly I noticed them getting very hot, I am worried it might get damaged, please help I am new to this and cannot seem to find any answer. Also my old pc power supply got damaged which I was using to power the setup with I replaced with a 12 volt 2 amp power adapter, could this change be the reason for the overheat ?
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2 Answers
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The motor current is controlled by the driver. You can set the pot on the driver board to set the current as shown in the datasheet:
This is accomplished inside the driver chip by driving the coils with a PWM signal. If the coils were powered continuously from the 12V they would burn out because usually they're only rated for a couple of volts continuous. A 12V rated stepper would be objectionably sluggish.
In some applications the stepper current is automatically reduced when it is "holding" position, which helps keep the motors cooler. I don't know if your setup has that ability. In any case if you keep the surface temperature below 60°C you should be fine. If you intend to operate at higher temperatures you should consult the datasheet for the motor.
answered Jan 24, 2018 at 20:33
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The obvious reason for motors to get too hot is that too much current is being run thru them for too long a time.
Several possible fixes follow from the above:
- Run less current thru the motors.
- Run the current at a lower duty cycle, with the cycle period small relative to the thermal time constant of the motors.
- Use bigger motors that can handle the current without overheating.
That said, make sure the motors are really getting too hot, not just simply hot. Some elevated temperature is normal. I'd say anything you can keep your finger on for 10 seconds without getting hurt is not too hot.
How did you decide that it was OK to run 2 A thru these "CD drive stepper motors"? I expect they didn't come with a datasheet. Perhaps they just aren't meant for that much current. The dissipation goes with the square of the current. At 1.4 A, the rise above ambient should be half what it is now.
answered Nov 13, 2017 at 19:10
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\$\begingroup\$ I was under the impression, the motors will draw only that much current as required. Correct me if I my wrong, but as I have read in theory even if I provide lot of current the device would draw only that much current as required, it's only if the amount of current needed by the device is more than the rated amps of the power supply does the power supply gets damaged. Also I have tested the system with a PC power supply which could output 16amps on the 12volt rail without heating ! It's only when I short the wires of pc smps by accident and hence destroyed it, I switched to a 12volt 2 amp \$\endgroup\$ Commented Nov 13, 2017 at 19:19
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\$\begingroup\$ 12 volt 2amp supply, because I couldn't afford another smps and 12volt (instead of the 5 volt which I was using from the pc smps) as 12volt adapter is more common and the EasyDriver datasheet said it could take upto 20volt. \$\endgroup\$ Commented Nov 13, 2017 at 19:21
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\$\begingroup\$ I cannot touch the motors for more than a second without hurting myself, just after it's bieng turned off is it normal ? \$\endgroup\$ Commented Nov 13, 2017 at 19:21
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1\$\begingroup\$ @UditSarkar The motor doesn't self limit the current like that. The current drawn is a function of the applied voltage, winding resistance and speed (back EMF). If the motor is not moving (as is common in stepper motor systems) the current will be whatever the supply voltage is divided by the winding resistance. Double the voltage and you will quadruple the power dissipated in the windings. It sounds like you need to run it from 5V unless you have a current limiting controller or add some big heatsinks. \$\endgroup\$– JonCommented Nov 13, 2017 at 19:25
+5Vto power the steppers .... you use+12Vand you wonder why the steppers are getting hot ???? \$\endgroup\$