[charlieslasher]

Hi,

Is there a way to have the g540 fault if power to a stepper motor is lost?


i have a heavy z axis i need to release a brake and what to be fail safe in all circumstances.

Or a current monitor relay on z axis stepper wires is all i can think of if i cant get the g540 to fault.

thanks

[john-100]

if I was you , I would look into using a spring or gas strut to counter the weight of the Z axis

I'd expect a break in the wires to an energised stepper motor will destroy the stepper driver H bridges puting the G540 into the fault condition

I can't think of an easy way to monitor the stepper motor current or the G540 supply current to confirm a motor current has changed due to a fault
as the current will drop when the axis is idle , assuming the current set resistors are all fitted for 3.5A motors

John

[CoAMarcus]

John is correct; the G540, when FAULTED, will freewheel the motor. This sounds like the exact opposite of what you want on your Z axis, so a brake of some sort would be in order.

[charlieslasher]

John is correct; the G540, when FAULTED, will freewheel the motor. This sounds like the exact opposite of what you want on your Z axis, so a brake of some sort would be in order.

When faulted is ok as i can get a signal to release/clamp the brake from g540/mach3. But how can i get a fault signal if i cut a motor cable. When i disconnect motor cables now from g540 i get no signal or fault. Just trying to cover all situations. sampling current with hall effect sensor seems like a non contact way to go.

[phomann]

Hi,

You should be able to put an electric brake on the motor and use one of the G540 relay outputs driven by the Mach3 Enable output to release the brake when the G540 is disabled, when Mach3 is in Reset.

As to detecting if a motor wire becomes unplugged, you need to solve that problem by ensuring that it doesn't become unplugged. If necessary you can buy cable designed for continuous flexing that will not fatigue like standard cabling.

When a motor is unplugged while operating, there is a good chance that you will damage the drive for that axis. I recenly repaired a G540 where this occurred. I replaced the axis drive, but the motor movement was intermittent, making a loud clunking noise.

In the end I un-soldered the DE-9 connector off the G540 motherboard and when I did a continuity check on the pins, one was open circuit. The customer sent me the attached image of the mating connector.



It was clear from the image that an enormous amount of energy passed through the pins when the disconnection occurred, destroying the pin in the connector on the G540 and the axis drive.

Cheers,

Peter

[charlieslasher]

Hi,

You should be able to put an electric brake on the motor and use one of the G540 relay outputs driven by the Mach3 Enable output to release the brake when the G540 is disabled, when Mach3 is in Reset.

As to detecting if a motor wire becomes unplugged, you need to solve that problem by ensuring that it doesn't become unplugged. If necessary you can buy cable designed for continuous flexing that will not fatigue like standard cabling.

When a motor is unplugged while operating, there is a good chance that you will damage the drive for that axis. I recenly repaired a G540 where this occurred. I replaced the axis drive, but the motor movement was intermittent, making a loud clunking noise.

In the end I un-soldered the DE-9 connector off the G540 motherboard and when I did a continuity check on the pins, one was open circuit. The customer sent me the attached image of the mating connector.



It was clear from the image that an enormous amount of energy passed through the pins when the disconnection occurred, destroying the pin in the connector on the G540 and the axis drive.

Cheers,


Peter

Ok i will do this for starters. What do the spare pins of the db9 plug do? think they say ground wires. Could i run a input to g540 loop thru them that would detect if the cable was disconnected. Not sure if my cables have the wires but just another option.

I probably need to upgrade to servos eventually but this is what i am working with now. Really pushing the gecko and kelling steppers to the max and they just wont give up.