Duet 3HC Expansion looses Connection
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@T3P3Tony said in Duet 3HC Expansion looses Connection:
@developeralgo222 ok so it does look like that 3HC needs replacing as well. please follow the same process as before with an email to warranty@duet3d.com. I suspect the 6XD may actually have been ok, but we will have to see when we get ti back for testing.
Have sent an email to warranty@duet3d.com to have 2 x 3HC boards swapped ( Boards 3HC1 & 3HC3 ) . This boards don't seem to work correctly. Only Boards 3HC2 & 3HC4 work correctly with 6XD Mainbaord (replacement) and all cables tested including Kenable ADSL 2+ cables.
So far using any kind of recommended cable (Kenable ADSL 2+) or self-made cables as per the requirements, the only reliable and consistent results (Only with 1 PSU---24VDC, 20A) on the
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Isolated Test Bench have been:
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6XD(replacement) ====> 15m/1m (Kenable ADSL 2+ Cable) ====> 3HC2 (With CAN Bus Termination) =====> Works and Syncs without errors
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6XD(replacement) ====> 15m/1m (Kenable ADSL 2+ Cable) ====> 3HC4 (With CAN Bus Termination) =====> Works and Syncs without errors
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6XD(replacement) ====> 15m/1m (Kenable ADSL 2+ Cable) ====> 3HC2 ===> 1m (Kenable ADSL 2+ Cable) ====> 3HC4 (With CAN Bus Termination) =====> Works and Syncs without errors
Even reversing the Cable length order or 3HC expansion boards order , that still works
- PnP Machine : The above results have also been duplicated on the PnP Machine without errors so far.
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@developeralgo222 I don't know, and we probably won't until the returned boards make their way back to us in the UK, if a ground loop has caused the CAN malfunction, but is there a particular reason why you want to use two power supplies? For a pick and place machine, you're only moving axes and switching relays, generally, so I doubt there is anything drawing particularly high current. Usually it is the bed heaters and hot ends on 3D printers that create the need for high current, or multiple, PSUs. It just seems like an unnecessary complication.
Have a look at this wiki page to calculate what your system might draw: https://docs.duet3d.com/en/User_manual/Connecting_hardware/Power_choosing
Ian
TronXY X5S with Duet 3 MB6HC and Roto toolboard : Cartesian bed-slinger with Duet 3 Mini 5+ WiFi and 1LC : RRP Fisher Delta v1 with Duet 2 Maestro : Polargraph with Duet 2 WiFi
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@droftarts said in Duet 3HC Expansion looses Connection:
@developeralgo222 I don't know, and we probably won't until the returned boards make their way back to us in the UK, if a ground loop has caused the CAN malfunction, but is there a particular reason why you want to use two power supplies? For a pick and place machine, you're only moving axes and switching relays, generally, so I doubt there is anything drawing particularly high current. Usually it is the bed heaters and hot ends on 3D printers that create the need for high current, or multiple, PSUs. It just seems like an unnecessary complication.
Have a look at this wiki page to calculate what your system might draw: https://docs.duet3d.com/en/User_manual/Connecting_hardware/Power_choosing
Ian
In reality , i don't think PnP will draw that much power (2 x Nema 34 closed loop motors with 2 external drivers, 3 x Nema 17 stepper motors directly on Duet 3HC , 6 x Nema 11 stepper motors directly on Duet 3HC). I am OK to use just 1 PSU (24V,20A ) but it might be cutting it a little close as per the actual power draw requirements and calculations. Once i have everything setup completely and working i will see the actual max power draw when the machine is in intensive PnP operation.
For now, both the Isolated Test Bench & PnP Machine , i am just using 1 PSU each to make things simple. I perform all the tests on the Isolated Test Bench and once a 3HC Board passes all tests then its moved and added to the working boards on PnP Machine and tested again to confirm that it works as expected on the PnP Machine and i will only add a second PSU if i am gettting close to 80% of the rated 20A (16A) on the PSU1.
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@developeralgo222 said in Duet 3HC Expansion looses Connection:
Does that mean we have an issue with the way the CAN-FD is designed on the Duet Boards ? Does Duet boards have some protection designed in them to mitigate that issue ("undefined potential") as per your explanation above ?
Only optical insulation can provide this level of protection. This is usually done by optic fiber transceivers, and of course, optic fiber . These modules were not designed for such environments, nor they should/need to be. Except an human error, like in this situation, they should perform optimal, the way they are designed.
If CAN signal needs to be sent over long distances, and/or over big voltage differential, or in a really very, very noisy environment, only then such optical insulation is justified. In a machine like... most of ours, it is not the case. Working with 300kV (let say), for ozone generators, then we are talking another level, and then, those transceivers are justified.
Those undefined potentials, could very easy destroy some protection diodes, wich are calculated for a certain range, wich can be checked in chips specs. But the event ”happened” here, for sure surpassed the specs of the chips protection.
The interesting here is that the problem generated, can be (in appearance) very strange and inconsistent. One only can pray electronics boards to ”survive” after. In your case, you had not do it hard enough, if I may have a joke at this ”funeral”.
Sorry, but, no offence, I did not assumed too much. I myself done such stuff, so many more than once. Experience comes with a price ... usually.
L.E. The boards have a protection for common mode signals, L7, in a certain range of frequency.
However, adding a protection for what you would have needed, would mean (for example) some series resistors on the bus, to limit the current in the protection diodes (wich exists, inside the chips).
As the voltages may be relatively big (tens of volts or more, in this case with 2 PSU, without ground wire), the resistors should be in the range of (tens of?) kiloohms, wich would impair the speed of CAN so much, than it would not be usable for high speed communication (or even for low?), especially for somewhat longer cables, like 4-15m, as the parasitic capacitance will increase with length, but I suspect even for shorter ones it would be true.
Not to talk about adapting the bus (those terminators) in such a case...
In any case, nobody in the industry is doing such a thing, as it is not useful.L.L.E. Isolating CAN Bus
One may jump directly to Conclusions, but the paragraph about Sources of failure, is a good read too -
@developeralgo222 can you confirm that the replacement boards have solved the problem?
I have the two 3HC and one 6XD boards you returned set up on the bench and connected them together using two Kenable CAN cables. Both 3HC boards had the termination jumpers installed when they arrived, so I removed the jumpers on the middle board. They are all syncing reliably. I will look at the CAN signals on an oscilloscope later to check that the signal levels are correct.
