grounding...

[Skip]

Vanish, you are correct, thank you for pointing out my error

 

I will add, I thought the the "skin effect " was a function of frequency only, not voltage.

 

I would like to know if the transmission lines you mention are

operating at something other than 60 hertz.

[royboy159]

Hey Van---It sounds like you type from working experience.

I know corrosion doesn't slow high voltage down much. Is there a prefered method to making a good high voltage bond? Thanks,roy:)

[karinvail]

this is an interesting thread. So, what grounds were 'stock'? I am thinking that the only ground I have is the one from battery to starter/transaxle and one small one from body to engine.......

[85Sub4WD]

Tinned wire is a VERY bad idea for cars - not nearly as good a conductor as copper, and the corrosion resistance on roads does not require such extreme means - obviously never use aluminium wire

 

soldering IS the best connection out there - if it is done properly with a high-lead content flux (provided it is not in a high temp area) - cold solder can cause connections to break, but properly soldered wires are MUCH stronger than crimps

 

that said, use your standard crimps available, marine grade is generally the same stuff but priced higher (there are exceptions) - I have been working on boats a lot the past few summers in Key Largo, Florida, and they sit year-round in high salt/UV conditions - most all the stuff ends up the same in the end

 

Skip, Vanislru - I am very impressed at your electrical knowledge, I am studying Electrical Engineering, and some who have earned their batchleor's degree still don't know the elecrical differences between stranded and solid wires!

 

BTW - THHN wire used in conduit would be a good choice because it has three layers of insulation (I know the first is supposed to be at least somewhat oil/water resistant) and the insulation is rated for 90-degrees celsius

[Ross]

if it is done properly with a high-lead content flux

 

Or high silver content for a silver based solder. Lead based stuff is being phased out, wit silver based solder replacing it.

not sure if this is happening in the US yet, but lead based solder wont be available in europe soon.

[85Sub4WD]

Or high silver content for a silver based solder. Lead based stuff is being phased out, wit silver based solder replacing it.

not sure if this is happening in the US yet, but lead based solder wont be available in europe soon.

yes, it is happening here too - some of the newer fluxes are absolutely horrible, but silver is very good

 

I recommended lead because of its low melting point (which makes it easy to solder with), and because of how cheap it is

 

silver is an equally good conductor, and is probably safer too - I think it has a higher melting point though, which would make it more difficult to solder with

 

most all the soldering I do is for fine connections, and I have to be very careful as to how much heat I can apply, so I like a low melting point

[royboy159]

this is an interesting thread. So, what grounds were 'stock'? I am thinking that the only ground I have is the one from battery to starter/transaxle and one small one from body to engine.......

Hey kar---Almost every electical/electronic device on a vehicle has an insulated ground wire (usually black) running back to common grounding points on the body. From there it follows the grounding cables you noted.

[samo]

This is a bit late in the thread, but I upgraded the grounding system on my Subaru with a 1/0GA cable from the battery to the chassis and 8GA cables from the alt bracket, transmission, both heads, and the lighting relay pack I added all to ground. Seems to run a touch smoother, and it certainly can't hurt.

[Hank Roberts]

>silver

Yes, in California I've been using fairly low temperature silver rosin-core solder for all my electrical/electronic work, it's readily available.

 

Much, much safer now and down the road.

 

I've also been using "hard" silver "solder" -- it's actually silver brazing, the bond interpenetrates the metal surfaces rather than just stucking to them -- much higher melting points -- for jewelry/sculpture soldering of brass and stainless steel for many years. But for those silver mixes, you need to get the metal red hot -- and then drop the piece into boiling water to blast the much nastier flux off, so it won't corrode in a few years' time.

 

I suspect that the boiling water would be good for cleaning any soldered electrical connection -- it makes the flux remaining on the joint literally pop off, leaving a much cleaner surface than I can get if I just let it cool even slightly and then try to sandpaper it clean. The water has to be actually boiling for this to work on sculptural soldering, however.

 

 

I want to get myself a meter and start checking all the resistances between various points under the hood and the negative battery terminal, having seen people report these numbers start increasing after a few years as the ground starts to corrode.

 

Maybe some day we'll have sensors on our sensors, to detect failing ground connections on our sensors .... "and so ad infinitum."

[NorthWet]

A few notes from my reading this thread:

 

Do NOT use "dielectric" grease; dielectric by definition is electrically insulative. Use a conductive grease instead, such as "bulb grease".

 

Solder will make a mechanically stronger joint than a simple crimp, but as was pointed out it also causes a sharp stiff-to-flexible transition that will be a major stress (and failure) point unless some form of strain-relief is used.

 

Silver is a MUCH better conductor than lead, so a high-silver content solder will probably conduct better than a high-lead content solder. And, yes, silver solder has a significantly higher melt-point than does lead-based solder.

 

Something not yet brought up is that more grounds is not always good, and in fact can cause all sorts of mischief. More grounds creates more electrical return paths, each with its own resistance, however slight. With current flowing through resistance you get voltages. This is not usually a problem with simple loads like motors and lights, but can wreak havoc on the functioning of electronics like ECUs and sensors.

 

In a (my???) perfect world, all devices would have their own power and ground leads, or at least be part of a hub-based power-and-ground setup. (e.g. - The ECU gets a power and ground, and then provides power and ground lines to its sensors/actuators.)

[Hank Roberts]

I love the Kurt Lewin quote.

 

I haven't seen anyone post about grounding the ECU itself, til your post.

 

And, since I'm just about to pick up a friend's 1988, which had the ECU's internal ground signal blown up -- ECU had to be replaced, and the new one properly grounded -- this interests me.

 

I do worry about ground loops -- too many different contact points to the frame would be as bad as too many different ground rods hammered in around a house, I'm sure current flow between them would be a big problem.

[royboy159]

Hey Hank----Thanks for the soldering lesson

>

I want to get myself a meter and start checking all the resistances between various points under the hood and the negative battery terminal, having seen people report these numbers start increasing after a few years as the ground starts to corrode.

If the resistances on the 1X meter scale from an electrical/electronic components ground terminal to a bare metal spot on the body always measure less than 1 ohm, then your ground is good. Make sure power is off to the component.

[NorthWet]

I love the Kurt Lewin quote.

...

I do worry about ground loops -- too many different contact points to the frame would be as bad as too many different ground rods hammered in around a house, I'm sure current flow between them would be a big problem.

I can't claim credit for finding the quote... it was on the wall in one of my 16YrOld's classrooms. However, I do agree with it wholeheartedly. I also believe that you don't really know something unless you can explain it clearly to another.

 

Ground loops can be pretty troublesome. Just think of the corrosion potential... (pun not intended, but seems appropriate now that I noticed it).

[royboy159]

A few notes from my reading this thread:

 

Do NOT use "dielectric" grease; dielectric by definition is electrically insulative. Use a conductive grease instead, such as "bulb grease".

I've never had any problems with dielectric but then I never used it on low voltage applications. Off to find "bulb grease". Thanks:)

[NorthWet]

I've never had any problems with dielectric but then I never used it on low voltage applications. Off to find "bulb grease". Thanks:)

Your "dielectric grease" may be the same thing as my "bulb grease"... I recently ran across this confusion at a parts store, but did not try what they were suggesting. True dielectric grease is usually used to allow thermal conductivity but electrical isolation (as in transistor heatsink compound), and would be worse than smearing bearing grease on the connection.

 

The most common automotive use for dielectric grease would be around sparkplug boots where you want the seal but absolutely no conductivity.

[royboy159]

Hey NorthW----This is interesting. My dielectric by Dow Corning is recommended for auto ignition systems and electrical contacts of power distribution units. I've used it accordingly but not on anything less than 12 volt. I have no idea of the science behind it.:-\

[Vanislru]

A good compound for auto connections is Noalox, or Penetrox [tradenames]. Both are available at home depot or an electrical store of some sort. It's mostly used for aluminum connections to prevent oxidation of lugs/conductor surfaces, it has high conductivity and is resistant to breakdown. Excellent for battery posts, starter lugs etc... and recently they've started selling small tubes of it [25 ml?] so yuou don't need to spend alot either.

[Hank Roberts]

I've also got to mount my ham radio antenna (I'm N6VSB) -- looking into this, I've found you can have a good DC ground electrically that is still not a good RF (radio frequency) ground for ham radio operation.

 

Here's a discussion (follow links therein for much more detail):

 

http://www.k2bj.com/Ground.htm/

 

He's using flat copper braid, tinned, for grounding all the parts of the vehicle together -- hood, trunk lid, several places along the exhaust, and so on. Remember this is grounding radio frequencies (the vehicle is serving as the 'ground plane' for the ham radio antenna).

 

He has a good discussion of electrical ground and ground loops as well.

 

--

 

And a note on terminology -- "dielectric" is confusing, it's actually a term that needs a number with it to describe how much electric potential is needed to cross it; there are highly insulating dielectric greases sold apparently for spark plug connections to 'keep the electricity inside' -- they allow the current to go where it should but not find other paths. There are specifically conductive greases.

 

There's the high end six ounces for forty dollars stuff (!)

 

http://www.2spi.com/catalog/vac/silver-filled-grease.shtml

 

(silver when it is an oxide's still a conductor; copper oxide is an insulator)

Whew!

[operose]

I've also got to mount my ham radio antenna (I'm N6VSB)

 

KC2HWI here, although I haven't touched a radio in a couple of years :-\

[royboy159]

I've also got to mount my ham radio antenna (I'm N6VSB) -- looking into this, I've found you can have a good DC ground electrically that is still not a good RF (radio frequency) ground for ham radio operation.

I'm learning something new every day. I was told years ago that RF "voltages" made corrosion impedence a miniscule problem. Appears not true.

And a note on terminology -- "dielectric" is confusing, it's actually a term that needs a number with it to describe how much electric potential is needed to cross it; there are highly insulating dielectric greases sold apparently for spark plug connections to 'keep the electricity inside' -- they allow the current to go where it should but not find other paths. There are specifically conductive greases.

I'd guess my Dow Corning dielectic is something in the middle.

[Hank Roberts]

More, excerpted from an article here: http://www.sailmail.com/grounds.htm

 

Inconsistencies in the Ground Rules

So now, you are annoyed with the inconsistencies. We said to leave all bits of immersed metal electrically isolated when we described electrolytic corrosion and hot marinas, but then we said to connect wires and copper tape to your keel and engine for lightning and RF grounds. So what to do?

 

RF ground. The RF ground needs to be a ground for RF signals only. It does not need to conduct DC, and as described in "Bonding and Electrolytic Corrosion..." above, you do not want to connect another DC ground to your engine and to your keel etc.

 

The solution is to find a dry secure place along each of the copper RF ground tapes that are running to your engine and keel. Fasten the tape securely to an insulating piece of phenolic or to a terminal strip, cut a 1/10-inch gap across the tape, and solder several 0.15uF ceramic capacitors across the gap. These capacitors will be transparent to the RF, which will be happily grounded by the ground tape system, but they will block any DC currents from running through the RF ground system, and will avoid any resulting susceptibility to hot marina electrolytic corrosion. It is worth selecting the capacitors carefully, because they may carry a significant amount of RF current. An acceptable choice of capacitors and vendor are listed at the end of this article.

 

........ Summary

By using capacitors to block DC connections in a few key areas, it is possible to have perfect ground systems for AC, DC, RF, lightning, and corrosion, and have a boat that is immune to stray DC currents that are traveling through the water in "hot marinas."

 

 

...

Capacitors for use to block DC in SSB grounding tape: Digi-Key, (800) 344 4539. Type X7R Monolithic Ceramic capacitor, 0.15uF, $0.91 each, Digi-Key part number P4911-ND.

[Hank Roberts]

and West Marine's got a closeout sale on this (expensive!) stuff, if you're near a store that has any or want to add it to your next yachting gear order ...

 

 

Heat Shrink Tubing - Adhesive Lined Ancor's adhesive lined tubing is superior to conventional heat shrink tubing. It bonds tenaciously to insulating covers and terminals,... 8 Items Clearance Priced - From $2.88 USD

[Hank Roberts]

Found here: http://www.innovatemotorsports.com/resources/electrical-grounding.php

 

QUOTING an excerpt, my emphasis added; see original page for the real info:

 

... wiring the electrical system in a car the best way is to run separate ground wires from each system to a common ground point. The common ground point should NOT be just a bolt where lugs from each device are stacked in top of each other. The contact patches between the lugs create their own resistance and ground problems. The very best way is to bolt a short piece of copper bar near the battery to the frame. Connect the copper bar to the battery with a heavy duty ground strap. Drill and tap the bar for each ground return. The heaviest current user in a car is the starter. It can take up to 800 Amps of current. So it should have its own ground strap directly to the battery. So should the alternator. Its wires carry the second most current after the starter.

 

Electronic fuel injection and ignition systems have their own caveats though. Ignition systems create very high current pulses for a very short time. This is especially true for Capacitive Discharge Systems. Those need their own ground wire to the common. EFI systems rely on different sensors in the car. Throttle position sensor, Intake and coolant air temp sensors, Manifold pressure sensors and so on. These sensors typically have 2 or 3 wires. When they have 2 wires, one is typically the signal and the other ground. 3 wire sensors need a 5V supply, signal and ground. DO NOT connect the ground of these sensors to the common ground as described above. The EFI computer, as any electrical device can only see its own ground and references all measurements to that.

 

The EFI computer also switches the injectors on and off. Injectors use relatively high currents, and these currents have to flow back to the battery through the EFI computer’s ground wire. This causes a voltage drop on that ground wire. Were the sensors grounded to the common ground as described above, the ECU would see only the sensor voltage minus the voltage drop of its ground. Instead ground the sensors directly at the EFI computer to its ground. Sensors only take a few mA of current anyway, so the additional drop on the EFI ground caused by them is irrelevant.

 

...

 

Audio systems in cars also need to be connected to this ‘star’ ground. The human ear is the most sensitive organ we have. The difference between the loudest noise (pain threshhold) and the quietest noise we can hear is over 1 million to one. So any electrical noise from inadequate grounding can be amplified by the audio system to hearing level.

 

.... The only effect a better grounding system can have is if the sensor grounding was so bad before that the EFI computer misread the sensors due to ground offsets. This can be inexpensively remedied by following the grounding guidelines above. .... END QUOTE

[royboy159]

. Injectors use relatively high currents, and these currents have to flow back to the battery through the EFI computer’s ground wire. This causes a voltage drop on that ground wire.

It took me awhile but now I understand why changing a grounding point, such as for the injectors, could upset the sensors' voltage drops and therefore change what the ECU does.

Also the full text article clarifies why sensor wires need protected from the induction produced from spark plug wires. Which having signal and ground wires running side by side accomplishes.

Thanks Hank:)

[Hank Roberts]

One of the bits I snipped out of that short quote reminds us that it's wise to twist the pair of signal and ground wires going between ECU and sensors, which counteracts the 'electronic smog' noise inside the engine compartment -- same reason that Ethernet uses 'twisted pairs' of wires, so any induced current flow where the wire is affected by some other electromagnetic signal is neutralized.

 

Spooky stuff going on under the hood!