Phidgets Forums

Hi,
I have a project with 5 VINT wireless hubs connected through Ethernet cable and it is all working, but not consistently. There are 18 stepper drives and 18 limit switches connected to 16x Digital Inputs along with a bunch of other things I haven't connected yet.
It basically has to run a 'home' routine to reference off the limit switches, then go to one of several predetermined sets of positions when buttons are pressed. ( simplified description )
I coded it in VB NET to not attempt any motion until all components are attached, and it works about 1/2 of the time without issues. The other half of the time some components will detach for no obvious reason and cause some potentially serious problems.
I had thought that there should be plenty of power there. The machine has 3 Phidgets 24vdc 15a power supplies, 1 supplying the first 9 stepper drivers (4a drivers) and 1 supplying the other 9, while the 3rd one is for control power like limit switches etc.
The motors are not heavily loaded at all and set to run at max 2.8a each, so am I too light on those power supplies? Now my basic math of 9 stepper drivers from a 15a supply only works out to 1.666amps per stepper. 4 amp drivers x 9pcs = 36amps... Am I wrong to think that maybe they are disconnecting because they are drawing too much? Could this be the source of my disconnect issues?

I'll put an amp meter on the supply with all the motors running and see what I get and post it here shortly.

Thoughts?

Dan H

I put a DC amp clamp meter on the line feeding 9 of the stepper drives and ran the homing routine, then sent the motors all to another position so they would all be driven at once at the speed that they will be running at and the amps drawn didn't exceed 5.6. It seems to me that there is still over 50% of the power supply capacity left over, so I would think that insufficient power is not the reason things are not staying connected.

Any ideas on what other causes I should be looking for?

Also, would there be a benefit to switching the Ethernet connected VINT hubs to the USB versions? Do those tend to perform better? They are all installed within 2 ft of the control PC, but I went with the Ethernet connection because I assumed it would be more stable than USB.

Thanks,
Dan

I would go with USB unless there is a good reason to go with the wireless hubs. The USB hubs are much simpler, and there is much less to go wrong on them.

As for the wireless hubs. I would make sure they are all up to date. When you say detaches - is it just the steppers which are detaching, or other channels as well? You could post the network server logs to give a better sense of what is happening.

-Patrick

It has been mostly the steppers detaching, but the other VINT devices have detached occasionally as well. Most critically, the 16x Digital Input VINT that reads the limit switches. Steppers still working while the limit switches are not is a bit problematic.
I bought and installed 5 USB VINT hub0000's, the 7 Slot Phidgets USB hub0003 and Phidgets beaded cables to connect them to the PC to try to get this system more stable. I had to put a short (<1 second) delay in each attach event before I did anything with the steppers, which was a new behavior but not a big problem.
It all attaches and runs better than it did with the ethernet connected versions, but the steppers controllers still drop far too often. I'm seeing about a 50% improvement with the USB version VINT hubs over the ethernet ones.
I read the "Improving_Phidgets_Hardware_Reliability" section and I am wondering if I have any ground loop issues? It said that should not be an issue with the VINT devices, but the USB hub0003 power supply is the same supply as the stepper drivers. Would that possibly cause a ground loop issue?
I'll connect that hub0003 to the control power unit instead and try that tomorrow.
Any other suggestions on what to try to get this thing stable would be most appreciated.
Thanks,
Dan

Separate power supply made no difference. Still dropping stepper drive connections randomly.

Dan