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TOPIC: Save Encoder Position on Power loss

Save Encoder Position on Power loss 2 years, 6 months ago #1452

  • shagmwp
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Is there a way to detect power loss and store the encoder value? Or is there a limit to how many times you can write to eeprom, other than the write-cycle limit?

Re: Save Encoder Position on Power loss 2 years, 6 months ago #1454

  • csearcy
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The Class5 motors have a status bit that can be setup with an interrupt to "attempt" to store position, but this may not work if the axis is in a rapid move when power is interrupted... as the motor may still be coasting... thus the position trapped may not represent where the motor was when it actually stopped moving.
There is a limit to how many times you can write to EEPROM... though it's a very high number (hundreds of thousands). When the limit is reached, the EEPROM location being written too may not retain it's value.

The preferred method is to use a motor with the -DE(Drive Enable) option. This method allows separate drive and control power inputs... so the drive power can be removed for safety... while the control power is maintained thus retaining the current encoder position... even if the motor shaft moves after drive power is removed.
We do have an absolute encoder option... but it is only currently available on certain "newer" motors.

Re: Save Encoder Position on Power loss 2 years, 6 months ago #1455

  • shagmwp
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Thanks for the quick reply!!

Is the status bit that you are referring to the Bo bit (Motor off)?

Which motors have the absolute encoder option?

Re: Save Encoder Position on Power loss 2 years, 6 months ago #1456

  • csearcy
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Bit 13 of Status word 6 is "Low Bus Voltage"... but this bit is only available in the Class5 motors(firmware revision 5.00 or higher).
Last Edit: 2 years, 6 months ago by csearcy.
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