Not 100% clear what you mean. I assume it's the machine not the display you are switching on and off?

By 'calipers' do you mean the displays on the read heads keep the correct reading?

The problem could be spikes on the mains power supply, it may be that the supply filter on the mill needs replacing.

I fixed a similar problem with my homebrew setup by fitting 10uf capacitors in the battery compartments of my read heads.

Neil

I wouldn't place too much faith in a surge protector myself to filter noise generated by the milling machine getting into the mains. The problem may well be some degradation in the speed control in the mill, for example a suppression capacitor failing so more noise escapes. Or even the brushes? A better bet may be to improve the filtering of the power supply to the scales/readout, possibly by simply a larger smoothing capacitor.

Hello Rik,

I would separate the dro power source from the machine supply. Feed it from a different socket to the machine, a source that might not be affected by the mill.

It may be worth changing the dro power supply to one that is more resistant to mains borne interference.

Regards,

Michael

Hi Rik,

I had the same symptoms and assumed it was an electrical problem. It was actually mechanical.

My display was mounted on top of the control unit. Switching off causes the contactor inside the box to drop out with a healthy thump. The vibration shook the usb cables sufficient to cause an intermittent connection. I found my plugs & sockets to be slightly loose at the display end, but not obviously so.

Your set-up looks to be less vulnerable to vibration than mine but it might be worth adding some form of strain relief to the cables to ensure that the plugs can't wobble.

Hope it's as easy as that!

Regards,

Dave

If I read the original post correctly the displays lose their marbles when the motor is cycled on and off? Presumably this is repeatable? That being the case it is unlikely to be mains borne interference, which by its very nature is random. I also understand that the DRO and displays are independently powered by batteries? I'd suspect either airborne EM interference from the motor drive or the DRO and/or its shielding being connected to the machine metal work and upsetting the differential USB signals via injected noise.

Andrew

PS: Just seen the post by Ian Phillips – makes good sense. The faster USB standards are fairly low impedance, 90ohms differential, so should be fairly robust against interference.

Edited By Andrew Johnston on 26/12/2015 22:06:23

Hi Rik i had a similar type of readout some years ago that died because of condensation getting inside it with all this damp weather it could cause a problem with it. As a aside i left a mp3 player in the workshop for a couple of days and that suffered the same problem, bought inside and after a couple of days it worked again.

Hi Rik,
I think the source of the problem is electrical noise generated when the NVR switch opens. (The NVR switch is the unit with the start and top buttons.) I would first try fitting a spark quencher across the contacts of the NVR switch. Such as this item My next step would be to fit a mains filter (such as this but with a suitable current rating for your machine.) if possible inside the control box of the mill or if there is not room then in a box very close to where the mains cable goes into the control box. There will probably be an earth loop formed by the fact the metalwork of the scales is connected together via the metalwork of the machine and the other end connected in the display unit. You could try just connecting one scale at a time to the display and see if the fault still occurs. If the fault does not occur with just one scale connected then make insulated mountings for one scale so it's metalwork is not connected to the machine. Although the connection to the scales uses USB cables the signals do not use USB protocol. They probably use a protocol called BIN6 which is a serial protocol. the data is on one wire in the usb cable and the clock signal on the other. I do not think the problem is caused by corruption of the data on the link. I think it is the dislplay unit electronics that is being effected.

Les.

Not claiming to be an expert in this matter at all. Only to say one of my friends had a similar problem. Ian took the lot off his mill and set it up on his wooden work bench no trouble at all, put it back on the mill and the problem was back again. So he electrically insulated each component of the digital read out from the metal work on the mill using paper, every thing now works fine. Could this be the answer ? John

Hi Rik, I think John is right. By connecting both scales to your mill you create a ground loop via the cables and the readout unit. This makes the readout sensitieve for spikes generated by the motor driver unit. Electrical insulating one or both scales from the mill meigt help solving the problem. You can easily try it by using some electrical tape. Regards, Johan.

Hello Rik, I too think John is right, insulation tape as suggested by Johan or a plastic sheet of some sort would be better than paper longer term. I would also consider connecting the earth terminal to a cleaner earth than the mill casting, a connection to the earth in the socket supplying the mill would be better.

One of those clear A4 covers that are used to protect documents in ring binders would be a good source of material.