Dg4s160-35 limit override

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Re: Dg4s160-35 limit override

Postby marteng » Fri Mar 30, 2018 3:45 pm

Ok, I have just ran the system with the servo motor power supply switched on and the "Power In" connector unplugged from the DG4S servo driver and only the green LEDs were flashing, i.e. system ok. I then re plugged the "Power In" connector again and the previous problem reoccurred. I think I should get in touch with the supplier.
In the mean time I would appreciate very much if anyone could shed some light on this.
Regards
Marteng
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Re: Dg4s160-35 limit override

Postby cncdrive » Fri Mar 30, 2018 4:52 pm

Are the red and green LEDs blinking alternately?
Is your motor move at least a bit when you plugging the power in?

If both answers are yes then you have the motor arms in reverse to the encoder count direction.
Try exchange the motor arm1 wire with motor arm2 wire.
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Re: Dg4s160-35 limit override

Postby marteng » Sat Mar 31, 2018 5:15 am

Hi, the green and red LEDs are blinking simultaneously and about the second the motors am not sure but it seems like there is a temporary connection of the motor. I will try your suggestion as the DG4S manual does not make any distinction between "Limit Over ride" and "Over current" (points 4.2.2 and 4.2.5) LEDs blink together / simultaneously in both cases.

I will let you know the outcome later on.
Thanks
Marteng
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Re: Dg4s160-35 limit override

Postby marteng » Sat Mar 31, 2018 10:31 am

Ok, so I swapped the motor terminations as advised but the problem still remained and the motor went to "Limit Over Ride" error. I then swapped back the termination on the motor and disconnected the BRKC-180 braking circuit and error was eliminated. I am 100% sure that the polarity connection on the BRKC-180 braking circuit is according to the manual, could it be that I need to reverse polarity on the BRKC-180 braking circuit?
Thanks
Marteng
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Re: Dg4s160-35 limit override

Postby cncdrive » Sat Mar 31, 2018 11:44 am

May I ask where is the BRKC-180 circuit is connected to?
I hope it is not connected to the motor output of the drive?!
The BRKC-180 circuit has to be connected in parallel with the power supply. The only purpose of the BRKC-180 circuit is to monitor the voltage of the power supply and to dissipate the regenerative power if the voltage gets too high.
So, the BRKC-180 circuit cannot cause a limit override unless:

1.) You have it connected to the wrong place. E.g. to the motor output instead of to the power supply.

OR

2.) You have about zero capacitance on the power supply or the power supply has a proble producing enough current and then the braking circuit can drop the power supply voltage to around zero volts and so the motor can't move without voltage.


And the braking circuit if it is connected to the power supply with the wrong polarity then you would already see smoke and damage of it, because it has no reverse polarity protection as reverse polarity on a device like that would need so bulky sized components that it is simply not affordable...
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Re: Dg4s160-35 limit override

Postby marteng » Sat Mar 31, 2018 12:27 pm

In fact that is what I did, i.e. connected it in parallel to the motor! Do you think these may have been damaged some how? Also since it is connected to the power supply, then I think only one is needed to take the back EMF from the motors. Am I right?
Thanks
Marteng
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Re: Dg4s160-35 limit override

Postby cncdrive » Sat Mar 31, 2018 3:17 pm

It's impossible for me to tell if the mistaken connection made damage to the breaking circuit or not, but if you did not see smoke then probably not.
You can also test the card if it is still working or not.
First connect it properly to the PSU and power it up and the LED should remain off. If the LED is on when nothing else is connected and if the voltage is below 180Volts then the card is damaged, then switch it off to avoid overheating of the breaking resistors.
It the LED is off then it is fine, then you can try to trigger it with shorting out those 2 THT resistors on the board, that will move the reference point for the voltage comparator to 0Volts and then the LED should light up and the breaking resistors are energised. Do not leave them shorted out, because it can overheat the resistors, just test it for a few seconds or so.
And be very careful what you touching, because depending on your PSU voltage levels there can be dangerous voltage levels which could harm you!

And if one braking circuit is enough or not depends on many factors, the power of the motor, the size of the load, the decceleration rate and frequency etc.
Basicly it depends on how much energy needed to be dissipated by the circuit.
The larger the motors the higher the load the more rapid the deccelerations the more they will enerise and the more the resistors will heat.
You should verify it in the application with testruns if the resistors heat up too much or not on the long runs.
If they do then you can any time install more breaking circuits in parallel, because they will share the dissipation.
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Re: Dg4s160-35 limit override

Postby marteng » Sun Apr 01, 2018 7:41 pm

Hi, for now I have isolated all the BRKC-180 circuits and inspected them visually and seem to be ok. I will be testing them later on so that I can keep on track with setting up the system for a test run which will follow after have tested and connected the BRKC-180 circuits where they belong.
I have noticed that one of the 4 motors that I have connected keeps spinning without raising an error, i.e. the green LED shows drive running normal. I have swapped the motor supply but still keeps turning, even without having Mach3 opened! I am not sure if this is normal, so tomorrow I will try to use another DG4S drive and see it does the same. The other motors stand still and offer resistance to turning their shaft so I know they are working as they should. Any suggestions?
Thanks
Marteng
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Re: Dg4s160-35 limit override

Postby cncdrive » Sun Apr 01, 2018 9:31 pm

If the motor is spinning and the limit override never triggers then the encoder on the motor is not counting.
That is the only case when the drive will not trigger a limit override, because if the encoder is not counting then the drive does not know that the motor is spinning, the servo error will not change with the motor spinning, so the motor can spin infinately without the drive knowing about it.
So, check the encoder.
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Re: Dg4s160-35 limit override

Postby marteng » Mon Apr 02, 2018 7:49 pm

Hello again, after further investingating the problem with the motor spinning, it resulted that the encoder was defective and needed replacement. After having it replaced all motors behaved as they should. Now I'll look into the BRKC-180 braking circuits and have them installed where they should be.
Regards
Marteng
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