Help identifying a resistor, probably

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My old man just send me a picture with the question if I could identify a resistor. But, alas I can not, it doesn't look like the color bands I know, nor can the internet help me very much.

It looks like it has 4 black bands. I only have the pictures, not the board it self, but could any of you tell me what part R13 is? It's from the system of gate opening device for a driveway.

I think it's a resistor, but I ain't even sure of that.

Attachment(s): 

Code, justify, code - Pitr Dubovich

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This is an average fried resistor. Ask the person who has the PCB to measure its value since it's almost sure the resistor is not broken, just fried a bit.

Warning: Grumpy Old Chuff. Reading this post may severely damage your mental health.

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Looks like a current sense resistor. Don't know this exact type but compare with:

http://www.irctt.com/file.aspx?p...

Something in the 0.001 Ohm or less region

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Okay, will do so. Thank you.

Code, justify, code - Pitr Dubovich

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Well there's the problem, your're missing D8 and D9 ! :)

It's difficult when you can't read the colors.
The 4th color band for normal resistors was:
absent: +/- 20%
silver: +/- 10%
gold: +/- 5%

The real issue, in my mind, is why did the resistor overheat, and was that its normal operating mode, or is it a failure mode?

Presumably he opened the cover because the device failed...

And presumably you asked him for all of the Model and serial numbers on the device so that you could attempt to get an on-line schematic.

JC

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It looks like a standard 100 Watt 0.00 Ohm 1% ressitor to me.

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Not to argue, BUT...

I thought 0 ohm resistors had a single black band.

And if it was a 0 ohm resistor why did it overheat, showing scorch marks on the PCB?

And, back in the through hole days weren't 0 ohm resistors pretty uncommon? (As a physical resistor, not as a jumper for single sided PCBs.)

Lastly, there are plain wire jumpers on the PCB, so if the design just needed a 0 ohm jumper why did they not use a plain wire jumper as they did elsewhere on the PCB?

JC

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JC,

I was perplexed by that burn evidence too, especially since the resistor has that 100 Watt rating.

I have a buddy who speicalizes in psyco-analyzing circuit designers and manufacturing engineers by examining their end-products. I'll ask him your question about the 0-Ohm versus wire jumper usage.

He is also very good at reading IC data sheets. Often after I've read the same ambiguous or disjunctive sentence ten times over and still can't make any sense out of it, I'll call my psycho-buddy for guidance. He has a special ability to peer into the writer's mind and can tell what the writer himself actually meant to write in the first place. Amazing!

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Quote:
I have a buddy who speicalizes in psyco-analyzing circuit designers and manufacturing engineers

Interesting... Very, very, interesting.

Focus now on the tip of my soldering iron.

It is hot, but you will not feel the heat.

It is smoking, but you will not smell the smoke.

It is What? ! Oh. Time's up. Back to reality.

Perhaps your friend studied under Uri Geller :)

JC

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100 w rating?

No, a 100w resistor is a great big ugly thing.

The largest known prime number: 282589933-1

It's easy to stop breaking the 10th commandment! Break the 8th instead. 

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Yeah, it's a bit of mystery I suppose, I am trying to get a hold of him to ask him a few more things. Thanks for the input so far!

Code, justify, code - Pitr Dubovich

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Torby,

Watts = P = I-squared x R

If I = 1,000,000 Amps and R=0.0000000000 Ohms

How many watts does that "0 Ohm" resistor dissipate?

What is the tolerance of the "0 Ohm" resistor?

5%?

0.00000000000 Ohms x 5% = 0.0000000000000 Ohms

See?

Now what do you think the power rating of the Zero Ohm resistor shown in the original photo is? 100 Watts would be quite conservative.

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Found here:
http://wiki.4hv.org/index.php/Re...

Quote:

Sometimes you might see resistors with all black stripes. Yes, these are zero-ohm resistors and are equivalent to a bit of wire.

Why use zero-ohm resistors? Sometimes it's purely a matter of aesthetics (or ego), as an avoidance of ugly wire bridges.

More commonly they are used because they are easier to handle - especially for machines. There's no point designing a new machine to handle wire bridges when bridges can be made just like resistors. This is even more true in the case where a factory produces two versions of a circuit, one with a few more features than the other. The two circuits can be designed with exactly the same circuit layout so that producing one circuit rather than the other becomes simply a matter of programming the production line.

I guess they should have power ratings because the conductors are not ideal. A 250VAC short-circuit will evaporate a copper wire about the thickness of the body of this resistor, that's because it's not superconductive.

The Dark Boxes are coming.

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Where is the problem to remove the resistor and measure it.Even if the resistor is broken and the colours can not identified you can scratch the coating and make measurments along the resistor body and since there is a linearity between resistor value and the length where the probe is attached the range value of the resistor can be found.