Drivers and motors getting very hot indeed

Hi all,

I've tried searching for an answer to this but didn't find one on the forums. But since this is rather straightforward, I apologize in advance if I'm asking something that is common knowledge here.

I've just built my own Sprite Desktop from parts, and so far so good. However, both the drivers and motors are getting very hot when used with LinuxCNC - all others software works fine.

In the manual that comes with the kit, the following warning is included:

Your MyDIYCNC Stepper Driver Modules use step, direction and enable signals to control your DIY Desktop CNC Machine’s stepper motors. However EMC2 can only provide step and direction signals. The electronics require an “on” enable signal to function. For the electronics to receive an enable signal EMC2 must be configured to send an “on” signal out the appropriate port for each axis, but it can only do so all the time rather than on demand. The net result is that the electronics are constantly enabled (as opposed to whenever they need to be in motion). This “always on” condition can cause the motor drivers to get quite hot. While they should still stay within operating temperatures, when using EMC2 it will be necessary to run the DIY Desktop CNC Machine with the electronics’ enclosure open to prevent heat buildup.

Thus my question becomes - is it possible to tweak this to avoid the heat buildup - either by messing with the code or through config options?

if your motors are becoming too hot , and i presume these are steppers which are and do run hot under normal circumstances , as dont forget they are energised at rest to hold position .
the chances are your current protection resistors or stepper driver current limit is incorrectly set for the stepper motor in question and it is drawing to many amps .

this is totaly a hardware problem and cannot be changed by linuxcnc or config etc
however if the driver has and enable sig , then this can be connected to amplifier enable pin and will only energise once linuxcnc is up and running , however this will not manage the over hot steppers or once enable is triggered
the steppers will be essentialy turned off , so can loose position .

so check your stepper current settiings and some cases stepper drives have a low current at rest or stationary switch , this may help .
steppers do run hot , but should not reach the point of lifting the paint !

Ok, thanks for the pointers. I'll check the hardware and see about the amplifier enable pin.

I guess the reason I assumed software issue is simply that other software (like Mach3) runs a lot cooler, but I guess simply strapping some cooling on the stepper drivers will serve to give me peace of mind

If MACH do operate the motors at lower temperatur, i am sure your Hardware does support a sleep mode and mach is using it, but you did not connect that signal in linuxcnc.

Search for sleep.

There is no reason that linuxcnc opperates the motors at higher temperatur,

Norbert

Sounds like a good idea. I'll take a look over the weekend to see if I can dig something up. Thanks for the help!

A good stepper driver should revert to a lower current if no step pulses for a given amount of time.
Which means the motor is not moving.

It should not be completely disabled. Then there is nothing preventing the axis from creeping. If it does, LinuxCNC (or mach3) will think the axis is at at standstill where it is in fact not. Then you have to home it again.

So if the driver have this feature it would be running full current if the software is stepping it in +/- direction while it should not be stepping at all. This would happen if the position hysteresis is too tight. I don't know what setting (if any) that would be in LinuxCNC. We would have to ask a grown up.

in this particular situation , i would worry more over the stepper controller than the actual stepper motors as they should be more resiliant to heat
as i presume the electronics came as a kit and would therfore be matched resonably well , stepper motors are designed to run hot , and can get suprisingly hot and still be in spec

if you feel the controller is becoming very hot , then i would fit a small pc fan to the case , it's benifical to have a fan drawing air across in any case , either way i cant see any longterm problem , if it does reach a high temp , then the drives should switch off as a safety measure and reset when cool ,thats then proven the situation to fit a fan to the case .

i feel as Andy does reading between the lines that they have used a pin ( enable here is probably the wrong definition ) to switch the drives into a lower current mode when the motors are stationary , the leadshine stepper drives have this ability internaly for example , or the pin is actualy used as an enable and therfore you loose position as your essentialy switching the drive off .

perhaps Andy has any thoughts on an output pin which is enabled only whilst motion is active or perhaps a macro triggered with M3 etc ,

do you have any specific information on the controller used ?

Hi! I think it is not correct to bounce Enable pins during a job. The Enable signal is not so fast at least, because there is need time to pre-charge some capacitors when awake driver in some cases. So LinuxCNC, when out-of-box, as i notice, deals precisely correctly with Enable pins, they (can be) released beween jobs but not during timed movements. And i not found any overheat at all (i use Sable 2015 / Panther 210 mill and TB6560 blue chinese board at 24 volts). If motors become hot when idle, then correct ways to solve is lower decay (rest mode) drive current of controller, and/or lower voltage; while lowering working drive curent will hot help, because we talk only about idle mode problem here as i can see. Also you may check schematic of driver board, if it too cheap then it may not have rest driver mode.
The information about "EMC2 can only provide step and direction signals" is incorrect (or old).

they have used a pin ( enable here is probably the wrong definition ) to switch the drives into a lower current mode when the motors are stationary , the leadshine stepper drives have this ability internaly for example , or the pin is actualy used as an enable and therfore you loose position as your essentialy switching the drive off .

One set of drivers I use has a high amp, normal and idle amp setting. I used hal to set signals based on the velocity of the axis. At stand still low amp. Medium speed normal amp. High speed High amp.

Rick G