Induction from spindle

I still don’t see how the arduino/ramps is inducing any voltage into the frame. Only alternating current, or moving dc motors can induce a current. There’s no meaningful ac current in an arduino. Now your power supply, that has ac, which stops at the power supply, then dc to the arduino. So, like I said, if you’re seeing voltage on the tubes, something is electrically shorted on your frame somewhere.

Yes, I understand. But I turn on power supply only and metal plate that I put under the brains box shows near 9-10 volts AC with ground. Then I connect box and see rise to 15-20 volts. It’s strange but it happens.

Anyways, problem that I raised in this thread is solved with two actions:

  1. Refraining from processing with accelerated speed
  2. using good SD card (chinese SD that I recevied with OEM printer was causing artefacts on display and perhaps had problems with delivering gcode into the processor)

This could be from all the new acceleration options we now have. That FR adjustment has always been wonky and I believe was put in more to slow things down, in case of a bad print, than to speed them up as speeding things up used to really mess things up as it did not obey the accel’s or max speeds. I am not sure where it is at now but the new equations are very complex and there are some issues without speeding it up already (Jamie, junction deviation?).

So good for a quick test, but I would never rely on this where money is involved, bits, material, precious time.

Agreed a bad card is annoying.

 

I highly recommend finding the source of that stray voltage as that is bad and could potentially be dangerous. I also believe this has to do with the Spindle PS. Maybe open it up (if you are knowledgeable enough to be safe)and look for the issue but this has come up more than once as a problem source. Some are good and some are horrible.

Actually that voltage on metal things in the area occurs there by air provided that one of PSs is on. And also working brains (arduino+ramps) add a few volts, I don’t know how but I witness it.

I can’t prevent it from happening but I can ground it.

Can you try measuring if you have voltage between your ground and your water pipes? BE CAREFUL: there is a potential for shock. This assumes your pipes are metal and tied into a large network, which is true for city utilities here but maybe not for you depending on your situation.

Some (most?) switch mode power supplies can produce high voltages (at low current) onto the ground input, or PSU case if there is no third prong. This is intentional to reduce electrical noise going back into the mains.

It might be possible that your earth connection is not making good enough electrical contact with the earth. If this is the case then your ground could be somewhat of a floating island.

If these are both happening then you could have voltage between ground and the “air”, not because the “air” is inducing voltage but because the ground is. If this were DC then it would not be a problem but with AC you will have some capacitance between different parts of your system and the “air” and then fluctuations in your ground will produce voltages within your system. This can produce intermittent problems that create misleading symptoms as the problem comes and goes (laptop/no laptop, etc).

You are definitely observing voltage between ground and “air” but it is unlikely that electromagnetic or electrostatic induction could cause these high voltages, so I think it is much more likely that the fluctuation is in the ground and not in the “air”. You could try a very long wire to measure voltage from ground to a metal object far away. I would predict that you would see similar voltage, which means it is not being induced through the air to the metal object, but that the ground is carrying the voltage.

As for a solution, if you have a voltage between ground and your water pipes, then try using your water pipes as ground.

If you don’t have metal water pipes then try this configuration:

  • Isolate your PSU cases from everything else
  • And do not connect the ground wires (third prong) of the PSUs (if any) to each other or to anything else
  • And do not connect DC negative of spindle and stepper supply together
  • You can still tie RAMPs ground (DC negative) to earth if you wish
  • This configuration is not safe but if you have no good ground then you are already unsafe. This configuration can shock you if you touch PSU cases, but your existing configuration can shock you if you touch anything.
 

I don’t have water pipes. I use “heatfloor” and fireplace to warm up.

No, if I ground with the ground insert that I made - then it is grounded well. I check that everytime if I do it before usage.

Such an experiment: I measure voltage between phase and ground - stable 220V (+/-2). I put steel plate 4mm thick, 300*300 on a wooden table in the vicinity of the PSUs and arduino/ramps. I turn everything off. Measure AC Voltage between ground and plate - 0V. turn on 1 PSU, measure - 4V. Turn on one more PSU - 8-10V. Connect arduino -> 12-15V. Is it not induction through air?

That’s a dangerous advise. I saw youtube explanation why should not do it. In general may be fine but if any device gets SC - you’re screwed.

I thought about that but wasn’t sure if that’s safe for the PCB.

On the contrary, since I grounded metal surfaces, MPCNC metal parts and cases of PSUs - I don’t feel any more sparkles when I touch something.

Here I can put some more information somehow connected to the topic.

I had one stepper to make sporadic steps without permission. Luckily I used deductive method and found that spindle feeding wire went across the stepper’s wire. When I moved them away 10 cm apart - error disappeared.

If the power supplies generate stray voltages into the ground wires, it could produce a different amount depending on the load. To prove that it is through the air from the Arduino you should move the plate far away from the Arduino and confirm that the voltage does not appear. If it still appears, then the voltage is in your ground wires and not in the air. If it does not appear when you move it away, then yes something is inducing through the air.

Exactly. I forgot to mention it but I did it and voltage on plate disappears when away. However, brains box was still close to PSUs so I can’t tell for sure which of the devices produce the most part of impact.