Out-of-tolerance zero ohm resistors

On a sunny day (Fri, 29 May 2015 08:13:23 -0700 (PDT)) it happened snipped-for-privacy@yahoo.com wrote in :

Try to but some with negative R.

They would have to be shipped with "keepers", like some supermagnets or big energy storage caps. UPS probably wouldn't allow them.

Marketing slogan: "Resistance is futile."

Cheers, James Arthur

The Keystone or Harwin parts are solid metal (in the clanky punch-pressed sense, not just like metal foil) and good for infinitely more current than... your puny PCB traces can do. :)

Tim

-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website:

You have nothing to lose but your ohms.

I did, they are, but thanks...

Cheers, James Arthur

On Fri, 29 May 2015 09:21:22 -0700 (PDT), snipped-for-privacy@yahoo.com Gave us:

You have to say that like Yoda in this instance....

"Futile, resistance is..."

On Fri, 29 May 2015 09:50:50 -0700, John Larkin Gave us:

"All electrons will be assimilated..."

Well, i have a serious problem stemming from those parts that are LESS that the nominal resistance rating....

On Sat, 30 May 2015 00:29:56 -0700, Robert Baer Gave us:

Would not "negative resistance" have some potential positive applications?

Just what is "nominal" for a "zero ohm resistor"?

Should you be nominated for being "problematic"? :-)

Just an observation.

I want the ones that are -1%.

A 1210-size 2oz copper trace will have a temperature rise of 45C with

On Sat, 30 May 2015 15:07:17 -0500, John S Gave us:

S*it, man! Just put a poly fuse in there! ;-)

Where do you get zero-ohm Harwin resistors?

Sound like the substitute parts are skimping on the Siemens, using only

Cheers

Yeah, they took lhe line of least resistance. No, wait....

Cheers

Phil Hobbs

Are you perhaps calculating for a continuous, round, equivalent cross-section in air, where the adjacent sections are dissipating similar power, and with much less surface area than the wide, flat trace?

I calculate a 2oz. trace has a resistance of 273 microhms per square.

A 2.5 x 3.2 section 2oz. trace--comprising 1.28 squares--would have a resistance of 349 microhms, drop 36mV, and dissipate 36mW @ 10.2A. That's not awful.

(Not quite as good as the Keystone zero-ohm part, granted.)

The siemens-deficient substitute part, however, dropped 125mV @ 10.2A, dissipating 1.28W. Even so, that part's temp. rise was only 15C referenced to the heat sink 1.5cm away on the other side of the board, and only ~7C (IIRC) over the surface the offender was mounted on, all measurements in dead air & insulated with bubble-wrap. (The heat sink is 1/4 inch aluminum plate, in thermal contact with a 50x60mm heat-generating patch of the board.)

Accordingly, I'd expect temp rise of the 1210 2oz trace to be (very roughly) (36mW/1.28W) * 15C, or about .4C.

Cheers, James Arthur