Can a Long and THIN wire, cause voltage drop when vibrated??

[settra]

Hello forum. i have the strangest think going on.. I am running a CarPC that uses a 12v DC 200Watt ATX. i am powering that PSU, from the battery, with two 4m cables (positive and grounding). the wires are pretty thin. around 20AWG gauge (they are the same diameter, as the cables that the ATX connecto has).

If at stasis, the computer works perfectly. the wires do not get hot, or anything like that. now... IF i shock the wires a bit (vibrate them) , then the PC imidietly shuts down!

my PSU, has a low voltage battery protection, so it is supposed to auto-turn off, if the voltage is lower than 11.5V.

i have tried with shorter length of wire, and it works just fine...
Will this go away if i use Larger gauge cables??
thnx!

 

[Nigel Goodwin]

I would suggest it's far more likely a poor connection at the end of one of the cables - but I would strongly suggest you use thicker wire anyway.

 

[MikeMl]

Almost certainly, vibration is modulating the contact resistance at either or both ends of the cable.

 

[Nigel Goodwin]

Almost certainly, vibration is modulating the contact resistance at either or both ends of the cable.

Now that's a really posh way of saying a loose wire

I'll have to make a note of that and steal it!.

 

[4pyros]

I hope you have a fuse at the battery so your car doesn't catch fire.

 

[Nigel Goodwin]

I hope you have a fuse at the battery so your car doesn't catch fire.

Not to worry, he's not in the USA

It's only in Americas that cars burst in to flames if you give them too stern a look

 

[settra]

haha dont worry dying by fire on the car, is far more unlikely, than dying in a car accident... :/
It turns out , that it was indeed a bad connector problem... although i also agrre that the shcoks could cause the wires resistance to go up.. i tried 3 Molex connectors (The 4 pin connectors tha PSU's have), and all had that problem (the wires were also soldered just before the molex connector).. as soon as i changed the connector, to a normal screw terminal, i no longer have that effect... :/

 

[MikeMl]

I have worked on aircraft avionics most of my life. You would be surprised what happens to connectors when subjected to the vibration caused by a slightly off-balance propeller. Most connectors used in aircraft are Gold plated. Molex are a no-no.

 

[settra]

Seems so... and i cant even start imagining a reason why... seems that a man, cant even know, how many things he dosent know!!

 

[4pyros]

I know enough to know what I don't.

 

[KeepItSimpleStupid]

Yep. I will tell you that a fan in an environmental chamber made havoc with me trying to measure in the range of Picoamps (1e-12 Amps). I had to tape all of the wires down.
It's called the triboelectric effect. Graphite impregnated triaxial (2 shields) help with the measurements. The graphite helps with the piezoelectric and triboelectric effect. The measurements went "a lot better" when I counted the number of coulombs and divided by the time to get the current.

The measurements also got wierd when I could measure "something" on piece of supposedly clean glass. Acetone or water left a measurable film. I'm the guy that could measure the resistance (conductance) of a piece of paper and see it change with the amount of humidity in the air. So, at times the measurement had to be performed with an overpressure of nitrogen to keep the humidity out.

 

[settra]

hehe i also had set an experimental aparatus for photoelectric effect wich mesured Pico Amps... whenever i so much as touched the cables, the measurments would go off the charts
Anyway, thanks allot for your help and feedback guys!