[How-To] Switch power for servos motor

[Cadillac]

So I recently got plans for a diy cnc plasma table. The issue I’m having the wiring diagram is basic. There are no safety interlocks or e stops. I’ve seen some videos and they state that when a servo motor is at rest both sides are energized to lock the position on the servo. Well that gets them hot if at idle for awhile. Some have put switches to turn off the motors to combat this. My question is where would you switch the power? Input to the drivers? Or output from driver to the servos?
Then my next question is would it do anything with positioning if the torch head wasn’t moved? If it was moved homing would be the solution. Any input would be appreciated thanks.

 

[Reddinr]

Definitely NOT the output of the drivers. Opening a switch in the output can cause a voltage surge that could knock out your driver's output transistors or chips. What drivers are you using? Is there a current setting resistor or input terminal to the drive? Is there an option to program in a lower hold current? Also, just because it feels pretty warm does not mean it is so terrible for the motor.

It is likely that positioning could change at least a little.

Also, are you talking about stepper motors or conventional motor servos?

 

[Cadillac]

I’m sorry for my confusion. They are stepper motors. The drivers are cheap drivers don’t see a brand but a model number of DM556. I honestly don’t know if the motors at idle overheat or not. But a majority of videos I’ve seen the builder installed on/off switches to the X and Y motors. My plan was to just use a E-stop button as so. What I’m hearing is I’d want to switch power to input of the driver? Thanks for the input.

 

[markba633csi]

Stepper drivers can usually be adjusted to limit the output current so as to prevent motor overheating at standby
and still deliver good torque

 

[Reddinr]

If you do switch it, do the switching on the input of the drive. A stepper will more likely keep its position when off if there is no force on the axis. The Z may creep more than X or Y. The steppers have weak hold even when off. If they are micro-stepped by the driver, you may lose an entire step (1.8 degrees for example) when the driver is turned off.

Do a quick search on DM556. I saw the model DM556T at stepperonline and a manual was available. Is this what you have? You can start off by using the minimum current you need for the setup to minimize motor temperature. You can set that on the dip switches. It only has to not lose steps during acceleration and motion to be sufficient. A few test runs can help you figure that out.

If I were building one I would probably just leave the motors on unless I'm not using them for a long time. This drive has ENA inputs. I think you can switch the ENA signals on and off vs. having the entire power switched off, but the DM556T manual I found was not clear what ENA does. SW4 of this drive can set the motor standby current to 50% automatically. That should pretty much eliminate any worry of heating the motors too long/too much. 50% current is like 25% power dissipated by the motor (roughly). If your motor went up 50 deg. from room temperature at full current, it would probably go down to about 12 degrees above room temperature at half current. The half current would very likely hold the motor in place unless the axis is physically disturbed.