B Can Cement Dust Cause Electrical Malfunctions?

[star apple]

A carpenter was grinding the concrete in the wall and the room so full of dust. Then the TV channel box malfunctioned.. is it possible cement dusts can become conductor when they covered the circuit board?

 

[f95toli]

Could it not simply be the case that the dust clogged up the vents or ruined a cooling fan? This would make the box rapidly overheat and possible also fail completely, especially if it does not turn off automatically if it gets too hot.

 

[berkeman]

A carpenter was grinding the concrete in the wall and the room so full of dust. Then the TV channel box malfunctioned.. is it possible cement dusts can become conductor when they covered the circuit board?

It looks like dry concrete is not very conductive:

https://www.google.com/search?q=conductivity+of+cement&ie=utf-8&oe=utf-8

What do you mean by "stopped working"? Does it have any LEDs that are still on? Is it just the RF part that doesn't work now? Is it a sealed box, or does it have vent holes that the dust went in through?

 

[Nik_2213]

In my experience, TV boxes tend to lack a cooling fan and 'run hot'. If a bad dose of mineral dust gets in via any vents, the passive heat-sinks are so going to clog up, perhaps enough for a failure cascade to develop.

Another possibility is the grinder, if electric rather than internal-combustion, was putting enough interference into the line to bollix the TV box. In that case, you may be able to unplug its power, wait several minutes, then re-boot the box...

( We've just had our big-name home-laundry machine repaired under contract after interference from the motor's worn brushes confused the micro-controller, which then accessed the speed sensor incorrectly and wrecked the motor. The initial symptoms matched a faulty door-latch sensor... )

 

[CWatters]

Another possibility is the grinder, if electric rather than internal-combustion,

An IC powered grinder could also cause problems when it's running, but it should be OK when its switched off (the box might need rebooting).

 

[CWatters]

Sorry if you have checked but... Perhaps the carpenter unplugged the TV box to plug in the grinder and forgot to plug it back in :-)

 

[star apple]

Hi, the tv box circuit board has no fan.. When I turned it on yesterday after the room covered with dusts from the grinding the day before, the channel just kept on changing or incrementing to the next continuously and the volumn kept going up and down.. but after I shook it and wiped, blew away the dusts (both the box and remote control).. it works again. Maybe just a coincidence. No possibility some form of dusts can be conductive (like carbons) and short circuits the very closed space pcb board electricals? Or short of metal dusts.. aren't there other dusts that are conductive.

Or better yet. What are the lists of dusts that are conductive?

Thanks.

 

[Nugatory]

Even if the dust is not especially conductive on its own, it can absorb enough moisture to conduct. The standard cure is to blow the stuff away with compressed air, but it seems as if your shake/wipe/blow treatment worked here.

You never want to allow dust, whether conductive or not, to build up on any electronic equipment. Even if it doesn't immediately kill the device, the stuff is often somewhat corrosive and will damage exposed conductive elements. And drop cloths are cheap.

 

[Baluncore]

The rapidly changing current shows that it had a channel change button held down. That button might be on the front of the box and have been pressed against something temporarily. The button might have been on the remote control, where was that? did it have dust on the buttons? Did it have capacitive touch keys?

 

[star apple]

The rapidly changing current shows that it had a channel change button held down. That button might be on the front of the box and have been pressed against something temporarily. The button might have been on the remote control, where was that? did it have dust on the buttons? Did it have capacitive touch keys?

It's just normal push button remote. I'll video it when it happens again. The tv box is not pressing on anything. Maybe it's the remote? But the volume increments by itself too and the channel too. Hmm.. maybe just a temporary remote or tv box malfunctions. It's ok now.
By the way. I remembered something that happened years ago. So i'll ask about it.

Can burning soot from any material be conductive.. because once an electrician was trying to live wire a circuit breaker. And it sparked and his fellow electrician said the previously burnt surface must have soot that have shorted the circuit breaker inside. Don't worry. I don't fix anything electrical. I'm just asking what kind of dusts are conductive.

Thanks.

 

[Nugatory]

Can burning soot from any material be conductive.. because once an electrician was trying to live wire a circuit breaker.

Soot is carbon. It's conductive.

 

[star apple]

Soot is carbon. It's conductive.

can soot from none-conductive plastic become conductive?

what none-conductive materials can produce conductive soots?

 

[Baluncore]

can soot from none-conductive plastic become conductive?

Yes. If you burn any carbon based polymer you get carbon soot. Carbon was used as electrodes in batteries and as carbon arc lights. Carbon is added to some materials to prevent build up of static electricity.

 

[Nidum]

Blocking or corruption of the optical signal from handset to receiver causing random responses of the receiver including possible shut down ?

or

Receiver is already in shut down condition and doesn't wake up because optical signal from handset is blocked or corrupted ?

 

[star apple]

Yes. If you burn any carbon based polymer you get carbon soot. Carbon was used as electrodes in batteries and as carbon arc lights. Carbon is added to some materials to prevent build up of static electricity.

Are circuit breakers made from carbon based polymer plastics whose soot can become conductive or are they made from non carbon based polymer? And what are these non carbon based polymer plastics made of?

 

[CWatters]

Google found...
https://www.galco.com/comp/prod/circ-mold.htm

The Frame, also known as the molded case, provides an insulated housing to mount to mount all of the circuit breaker components. This will often be made of a glass-polyester material or thermoset composite resin that combines ruggedness and high dielectric strength in a compact design.

A lot of wire has PVC based insulation (contains carbon) but there are others..
https://www.performancewire.com/insulated-wire-protection/

 

[star apple]

Google found...
https://www.galco.com/comp/prod/circ-mold.htm

Does this mean for normal circuit breakers, they are made of carbon based polymers or are all circuit breakers made of the above?

A lot of wire has PVC based insulation (contains carbon) but there are others..
https://www.performancewire.com/insulated-wire-protection/

 

[Baluncore]

To put it simply, the vast majority of polymers are carbon based. Short glass fibres and mineral fillers are often used to reinforce the moulded material and so give it dimensional stability. A contact arc will generate UV which will damage any polymer binding material.

A UV resistant ceramic or glass might be used, but it is more brittle. Also, if a switch opening arc is not extinguished fast enough, metal particles from the arcing electrodes will sputter any insulator surface and result in failure of the insulation. That is one reason why AC power distribution is used, it will extinguish when the phase reverses. The reversal will be within 10 milliseconds, unless there is glowing soot nearby that maintains a source of ionisation.

Every mechanical switch has a limited lifetime. Reliable switches are bigger, take greater forces to operate and cost more. Domestic fittings have evolved to be a safe and convenient compromise.

All the detailed information you need is available on the web.

 

[Wes Tausend]

The most likely cause for the symptoms the OP describes are that the buttons on the remote got stuck down. The reasoning is that cured Portland cement particles are very crystalline and as a result the particle sharpness creates a lot of friction or even mechanical locking between soft surfaces. By taking the remote apart, the flat, soft, rubbery, molded key pad cleared of debris releasing the buttons to freely protrude back up through their respective holes.

Carbon conducts so well that a carbon fibered automobile body will work fine as a ground plane for an old fashioned aerial type am radio antenna, just as the metal bodies did. When a polyester/fiberglass body was used (on Corvettes for example), the antenna needed a ground plane installed under the skin to perform properly.

Another trivia carbon vs. switch event related to older autos was that the old ignitions used a now obsolete rotating spark distribution device (switch) called a distributor. Every spark had to jump a gap from a centrally fed rotor terminal across to specific cylinder terminals placed around it's outer circumference. It usually jumped to the nearest terminal, the path of least resistance and on to the correct combustion cylinder. Once in a while, after just a few thousand miles, the correct path to the cylinder developed a high resistance from some wear process, perhaps a defective wire or across the eroded spark plug gap itself.

The new path was usually along the inside of a dirty plastic cap (called the distributor cap) that covered the main distributor assembly. Pressurized fumes from an oily crankcase forced their way inside, up the distributor drive shaft. The new spark path led to an adjacent terminal and tried to fire (spark) the wrong cylinder and raw gasoline polluted the atmosphere from the misfired cylinder. In addition, once the spark began to occasionally follow a new crooked, oily path to an adjacent terminal, it formed an increasingly conductive carbon path like we have discussed above.

The new carbon path encouraged a misfire even when the original spark path and cylinder condition were somewhat corrected. So carbon tracking (switch failure) is the reason that the old fashioned distributor is no longer used. Todays ignitions each fire directly from their own coil, only spark across the spark plug itself with a much more vigorous spark, and are reliable far beyond the mandated "untouched" 100,000 mile mark as required by EPA.

Wes

 

[Baluncore]

Once in a while, after just a few thousand miles, the correct path to the cylinder developed a high resistance from some wear process, perhaps a defective wire or across the eroded spark plug gap itself.

A spring loaded carbon brush carried the HT spark from the ignition coil to the rotating button with the wiper arm at the centre of the distributor.
The rotating wiper in the distributor did not touch the plug electrodes, the spark had to jump a narrow gap before it reached the wire that carried it to the spark plug. Sometimes it preferred some other route across a contaminated surface or along a crack that held moisture, to another plug or the chassis.
In later models, a bundle of carbon fibres replaced that wire. That had sufficient resistance to suppress oscillations, and so reduced radio frequency interference from the spark plug and wire, which otherwise was, effectively a Lecher Line oscillator.

 

[Wes Tausend]

[

A spring loaded carbon brush carried the HT spark from the ignition coil to the rotating button with the wiper arm at the centre of the distributor.

The rotating wiper in the distributor did not touch the plug electrodes, the spark had to jump a narrow gap before it reached the wire that carried it to the spark plug. Sometimes it preferred some other route across a contaminated surface or along a crack that held moisture, to another plug or the chassis.

In later models, a bundle of carbon fibres replaced that wire. That had sufficient resistance to suppress oscillations, and so reduced radio frequency interference from the spark plug and wire, which otherwise was, effectively a Lecher Line oscillator.

Thanks for the tip on the Lecher line application and mentioning the use of carbon suppression wires.

I'm afraid I don't quite yet understand using the Lecher process in this regard. I have used it by using lengths of 300 ohm twin-lead antenna wire to form a specific frequency interference impedance trap or even an entire dipole reception for antenna use when I worked in electronics.

I thought the reasoning behind the spark plug carbon suppression wire was totally resistive to reduce excessive current spikes that cause em interference to am radio (like lightning does). I do know that stretching such fragile conductors by pulling on the plug wires is not good because a stretch can cause excessive permanent resistance. That can encourage the distributor crossfire we discussed earlier. A good plug wire should measure no more than 20k ohms with a good multimeter or should be replaced.

Distributors played a role in my high school physics education. I once built a dual coil distributor with the intent to improve high speed firing by doubling the dwell time for each coil. At high rpms the old V8 point-operated single coils did not have time to saturate well between firing.

So I modified a standard distributor by removing half the cam lobes and mounted a second set of points at a 45 degree angle to the originals. To make room, the condensers (capacitors) were mounted outside the assembly. The opposite rotor end was modified to pick up the second coil from a ring and this concentric second terminal ring centered around the original coil terminal on the cap, then fired half the spark plug terminals from the back of the rotor at 180 degrees. It worked, but at idle. I attempted nothing more than prove to myself that I could adjust the second set of breaker points to time the second coil to fire perfectly with the original coil by carefully gapping the second set. But because of the crowded cap arrangement, I was afraid of damaging my engine with crossfire at higher speeds and the crudely glued cap assembly was fragile.

I think I may have been able to submit it as my required high school physics project, but foolishly I never had the nerve to ask. Back then many instructors were extraordinarily sensitive to bad hoodlum types with incorrect haircuts or disgusting hotrods. I assumed my distributor wouldn't pass muster as worthy engineering, and had no other project. Later I was informed that omission "severely" damaged my physics grade for the year. It was bad.

Wes

 

[Baluncore]

I'm afraid I don't quite yet understand using the Lecher process in this regard.

The original metallic wires and spark gaps made a Lecher Line oscillator. The resistive carbon eliminated that source of RFI.

 

[Wes Tausend]

Ok, thanks. I hadn't thought of a Lecher line that way but I think I understand what you are getting at.

After all, a pair Lecher lines is really how a tuned antenna is derived. I know that the ignition coil has a characteristic decaying ring to it from each fire and that feeds the earlier metallic spark plug wire lengths in series through a couple of air gaps. The wire and gap delays probably would slightly modify the reactance, and therefore the tuning, like a series coil/capacitor. But the end result would be the wire would act as a half dipole antenna and each firing would radiate a series of decaying radio waves that would interfere with am radio stations. Even storm lightning has a radio frequency range associated with it. Does that sound about right?

Wes

 

[Baluncore]

Does that sound about right?

Correct. But your term “half dipole antenna” may be confusing. The spark plug wire is a dipole at all frequencies. It is only a half-wave dipole at one frequency.

 

[Wes Tausend]

Baluncore, thank you for the info on the Lecher/antenna relationship. I've learned something new to me.

Wes