Having a Grounding Issue


#1

I am having an issue with Grounding my ADS-B in the fact that when I do it locks up. When I remove the outside earth ground, it works just fine.

I am using one that I purchased from Amazon: amazon.com/gp/product/B00KX … UTF8&psc=1

https://images-na.ssl-images-amazon.com/images/I/91Ynk3IilsL.SL1500.jpg

Any ideas… Open to any of them.


#2

Further followup. For some reason I am getting 1.1 VAC from my Shield to ground, so for some reason. When I connect my ground to my ground source it the Raspberry PI locks up and does not work. I try swapping the polarity at the power input and no help? The only way it will work is to disconnect the ground… I have tried 2 different Lightning/Surge protectors on the antenna and get the same result. Tried plugging in to different power source and no help.

Has anyone else measured their voltage from the Antenna Shield to ground? If so, let me know

Thanks in advance.

Sparkie


#3

Odd, maybe you have a floating ground on your powersupply?


#4

would rather suggest that the earth to your home isn’t that great (not necessarily a electrical fault), hence why your getting a potential difference between the actual ground (earth spike) and your household earth. This can just be a matter of how far you are from your local substation.

Might be worth finding a better source of information on household earth setups.


#5

Floating ground / floating neutral is a hazardous situation, and carries risk of electric shock. In case a live wire touches body of any household appliance (due to insulation failure), the ELCB (earth leakage circuit breaker) will not trip & cut off power supply. As a result bodies of all appliances will be at full phase voltage, resulting in electric shock to any one touching any appliance.

Better call a qualified/licenced electrician immediately to check your home’s earthing system. It is good that you got an advance warning by virtue of your Pi failure.


#6

were both of the protectors the same model?


#7

the gas discharge device you can check with a meter just make sure its not shorting to ground 1 and a bit volts is no cause for concern.


#8

No, 2 totally different brands.

The other unit was an L-COM AL-NFNFB


#9

I would agree, but the problem is when I ground the unit, it locks up the Rhaspberry PI and unable to connect to it.


#10

Trying a different power supply was a great idea, tried that and no change… Also tried it with a different power cable between the Rhaspberry and the power supply. No Change!


#11

Yeah, the basic problem is that the antenna shield is probably electrically connected to USB ground and the PSU ground, so if there’s a potential difference between that and what you’re grounding the discharge device to then your PSU is going to be somewhat unhappy as it tries to dump a whole lot of current through that path.


#12

With that in mind, what do I do about it. I am above the average skill level and this one is kicking my but… I have been a ham for 30 years, FCC-General Radio Telephone, Worked repeaters and commercial radios, worked with TV, and worked airplanes where grounding is crazy… But this simple little thing is kicking my but… Not sure what to do about it.


#13

The house I live in was built in 1955. While troubleshooting an electrical problem with a ceiling fan, I found that one of the previous owners, because of an open common somewhere along the line, went ahead and used the bare ground wire as a replacement for the white common on that circuit.

Though it worked fine, I rewired the fan circuit so that it was wired properly. ie black/hot, white/common, bare/ground.


#14

What you have done is right and safe, while what previous owners have done was wrong, risky, and against electrical safety regulations.

Using equipment ground as replacement for neutral is against NEC (national electrical code of usa), and also against electrical codes of almost every country in the world, as this has potential risk of electrical shock.


#15

The easiest and quickest way to solve a ground potential issue is to use a unun (same thing as a balun, but is unbalanced to unbalanced) You will either have to do the calculations and build it, or maybe find a component one that is good at 1090MHz.

Don’t ground the surge protector to house ground. Take it to earth.


#16

I have already have an independent earth ground and that did not help at all… Will look into the unun and see if I can work something out… Would like to find one one line and maybe get an unun and a Balun and see how that works… It definitely needs to be grounded.

BTW, as a side note, I measured the vac volts of my Direct TV Ground and Cable Internet Ground. Both were in the very low micro volts. This is clearly an issue ONLY with the FlightAware ProStick.


#17

Another option is a USB Isolator. The issue is finding one for a reasonable price that will provide enough current and speed. That would at least decouple the RPi from the dongle/antenna shield.

Just out of curiosity, have you tried plugging the dongle to a different PC, then measuring the shield to earth?


#18

That balun is only a test - not a solution. A fact that helps identify the defect.

I do not see a list of every wire connected to the Raspberry system. Nor a description of every wire into the power supply. I do not see a description of how the Raspberry Pi digital ground connects to earth ground or even a chassis that contains it. Also which ground does the coax cable shield connect to.

Remember, even interconnected grounds are electrically different. So all grounds that connect to a Raspberry must be at a common point to avert ground currents in the Raspberry’s digital ground plane.

Forget silliness using surge protectors. Spec numbers make obvious it will do nothing. Its let-through voltage is probably 330 volts. That means it does absolutely nothing until voltage will exceeds 330 volts. A voltage that high means a Raspberry no long works.

Your symptoms are consistent with ground loop currents. If those currents, for example, pass across the Raspberry’s ground plane (called a ground loop), then the Raspberry must crash. Describe in detail how all grounds are interconnected. Only use a single point earth ground for everything. And always connect a Raspberry ground to receptacle safety ground. Verify that a connection from receptacle safety ground to earth ground is intact - measures almost zero VAC between them.

Find (or confirm it does not exist) ground loop currents. Appreciate that Raspberry’s digital ground is electrically different from wall receptacle safety ground, is different from single point earth ground, and is different from antenna ground. And all must be interconnected using methods that do not create ground loop currents.


#19

I think you may have hit the nail on the head, and I am trying an experiment to see what happens.

Connected Wires

USB Mouse
USB Keyboard,
USB ADS-B (Flight Stick Pro)
Power Supply (that came supplied with the Raspberry PI)
HDMI Monitor

I disconnected the Monitor and the problem, for the moment has gone away. The monitor was the only item that does not get its power from the Raspberry. I am guessing that either the Phase of the monitor is wrong causing some feedback. This is something I can deal with, not having my antenna grounded is something that I CANNOT deal with. Thanks for helping me think out side the box.

Sparkie


#20

looks like your monitor has some excessive earth leakage going on, good find though. I hate weird ones like that.