Dg4s160-35 limit override

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Dg4s160-35 limit override

Postby Pinko12007 » Tue Dec 05, 2017 8:11 pm

When feeding a dg4s160-35 goes into alarm limit override and even intervening on the programmed value the drive is not unlocked. How can I intervene at the motor and encoder level to unlock the drive? Thank you
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Re: Dg4s160-35 limit override

Postby cncdrive » Tue Dec 05, 2017 10:58 pm

A limit override means that the servo error ran too high, the servo error is the step/dir signals counts summary minus the encoder counts summary, in other words it is the position error measured from the commaneded postion.
The limit override is a serious error, because it means your motor could not follow the position where you commanded the axis, the servo error ran higher than the max.error parameter you setup in the drive.
If the limit override happens then you can reset the drive via the reset line or you can unpower the drive's digital part and power it up again.
The reset procedure is described in the DG4S manual, basicly you can pull the reset line low and then release the line and so the drive will reset.
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Re: Dg4s160-35 limit override

Postby Pinko12007 » Wed Dec 13, 2017 8:09 pm

My problem is that this alarm appears when the drive is turned on, before commanding any movement.
If the power is turned off, the drive does not go into alarm
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Re: Dg4s160-35 limit override

Postby cncdrive » Wed Dec 13, 2017 9:43 pm

If power is turned off then ofcourse the drive can't go to alarm, because it is then unpowered.
If the drive goes into a limit override fault even with the motor moving means that the encoder or the controller which sends the step/dir signals sends unwanted signals.
It is possible that the encoder is faulty or the card which sends the step/dir signals has an issue.

Or if the motor moves and so the drive goes into fault as soon as you powering the drive up, then the encoder is connected up in reverse, the A channel is mixed up with the B channel, so the PID controller moves the motor not to, but from the setpoint until the servo position error reaches the set maximum and the drive faults. If this is the case then exchange the encoder A with B connection to the drive or exchange the motor arm1 with arm2 connection. Exchanging one of them will do the same, both reverse the count direction.

It is also possible that the set servo error in the PID tuning was set very low, e.g. 1-2 encoder counts and so when the drive powers up it basicly immediately faults as soon as it starts running the loop and moving the motor a littlebit on startup. So, also check what the max. error parameter value is in the PID tuning.
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Re: Dg4s160-35 limit override

Postby Pinko12007 » Thu Jan 25, 2018 5:35 pm

I reconnect to this discussion, I 'tried to replace the dg4s with dg3s, with these works and does not go' in alarm, if I try to put the dg4s, same connectors, same programming of the pid, as soon as I go 'in alarm limit override
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Re: Dg4s160-35 limit override

Postby cncdrive » Thu Jan 25, 2018 11:04 pm

What is your max.error parameter value?
The drive goes to alarm if the steps counts summary - encoder counts summary absolute value is greater than the max.error parameter value.
So, one possibility is that the max.error value is so low that when the drive powers up and tries to power the motor and so the shaft moves a little bit it immediately goes to fault before the loop could even stabilize.
The other possibility is that step signals are being sent to the drive, so when it is powering up and receiving these steps then the position error counter goes higher than the max.error parameter before the loop could even stabilize.
The third possibility is the same as the previous, but the drive getting encoder counts.

If you tried to replace the drive with another using the exact same motor same encoder and same cables and the other drive not producing this issue then the 2nd and 3rd possibility is out, but the 1st one is still possible, so verify the max. error parameter.
And there is one more possibility that the encoder interface IC got broken, overvoltaged etc. and so it is false counting causing the drive to think the encoder is rotating, however it is a 26LS32 line receiver chip in the drive which is a robust chip, it damages from high overvoltage only, above 25Volts difference on the input lines.

And one more idea which comes to my mind, but this applies only if the motor is actually rotating some when powering up is that you have the motor arm1 and arm2 reverse connected,
so the drive is moving the motor away from the setpoint when it should move it to the setpoint and vica versa. But for this issue I'm assuming that the motor is actually moving a bit when you poweing it up and if this is the case then you simply have to exchange the motor arm1 with arm2 connection.
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Re: Dg4s160-35 limit override

Postby Pinko12007 » Sun Feb 04, 2018 8:45 pm

After the last tests, the situation is unchanged.
if I connect a dg3s8020 to the hdbb2 and uc400 (for not having problems I have also purchased the dedicated control card) the system works and the servo controls the motor.
If I replace the driver with the Dg4s16035 (the motor must be powered at 110v and then the dg3s is small) removing the adapters for the main and encoder from the cables with rj45, until I connect only the main and the encoder the LED signals green and then l 'encoder is well connected, but when I connect the motor and motor power plug the driver signals limit override even if the set value is 20000 and no motor movement is heard.
the question is: are there any link differences between the 2 drivers that justify the dg4s malfunction?
Do I have to send the driver for assistance?
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Re: Dg4s160-35 limit override

Postby cncdrive » Sun Feb 04, 2018 9:41 pm

No, there is no difference in pinout of the DG4S main or encoder connector to the DG3s drive's same connectors.
The drive only faults with limit override if the servo error becomes greater than the set value of the max.error parameter in the PID tuning.
If there is no motor movement then the only way to get this error is if the drive receives step signals or encoder counts right before it could even power the motor up, so then no motor movement will happen, but the drive will fault.

It is interesting that you wrote that you get a green blinking LED without the fault when the motor is not connected.
Could you please make sure that you have the digital PSU and the motor PSU grounds separated.
The DG4S using isolated grounds with internal optical isolation between them and if you connect the 2 grounds together may cause noise problems which might cause false signals.
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Re: Dg4s160-35 limit override

Postby Pinko12007 » Mon Feb 05, 2018 7:27 am

Last test: I 'directly connected the cards to the power supply but the result does not change, I' noticed that leaving the power supply attached but removing the fuse between power supply and driver the LED signals green. Furthermore, when the dg3s is turned on for a while it puts the motor under voltage, what the dg4s does not do is normal or does the program inside the dg4s not work?
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Re: Dg4s160-35 limit override

Postby marteng » Fri Mar 30, 2018 2:40 pm

Hi guys, this is my first post on the forum as I am currently 70% through building a cnc router using CNCdrives and am at the test / running stage. I too am experiencing very similar problems with the DG4S 08020 servo drives. My electrical supply setup is all segregated so as to have better control, i.e. all power supplies of servo driver cards, servo motor power supply all have their own dedicated MCB with the requred current rating. When running the control system with the servo motor power supply switched off everything is good and DG45 08020 drivers having only green LEDs flashing. As soon as Iswitch on the servo motor power supply, the red and green LEDs start flashing.

I still have the same results with the fuses before the servo motors removed so as to isolate them.

My next try is to unplug the power in connector in the DG4S servo drivers and see what happens.

Has anyone identified the solution to this problem?
Thanks
Marteng
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