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View Full Version : What is the point of zero ohm shunts?



Martin_H
01-28-2012, 02:53 AM
I recently soldered a pcb kit which included a few zero ohm shunts. They looked like resistors with a single black band and were used for things like bypassing the voltage regulator when using a regulated power supply.

What I found mysterious is why use them over a bit wire?

Phil Pilgrim (PhiPi)
01-28-2012, 02:56 AM
The reason for including them in a PCB layout is that they can be installed, when appropriate, with a pick-and-place machine. A small bit of wire cannot.

-Phil

Martin_H
01-28-2012, 03:01 AM
Thanks that makes sense.

PJ Allen
01-28-2012, 03:18 AM
Anybody else ever been told how "0-ohm resistors" (one band, black) were devised because "jumpers" as such weren't allowed on old mil-spec pcb's?
[Jumper = No; 0Ω resistor = OK ]

localroger
01-28-2012, 03:44 AM
If the circuit board doesn't have solder mask, there is a risk of a jumper wire shorting to the trace it's jumping. Zerohm's don't do that.

Saw my first Zerohms in the docs for a HP2100A minicomputer circa 1974 in my father's physics lab. They were soldered in place to do peripheral configuration.

Tubular
01-28-2012, 04:02 AM
They also buy a little extra flexibility with regard to number of layers. The ability to use 0 ohm shunts (and jump a track) can be the difference between having to fabricate 1 layer vs 2 layer pcbs.

erco
01-28-2012, 04:07 AM
http://www.ebay.com/itm/ZERO-OHM-Resistors-Lot-50-0-0-Ohm-Jumper-BONUS-/230736589626?pt=LH_DefaultDomain_0&hash=item35b8f8f33a

Fifty zero ohm resistors costs ~$7. Sometimes less is more, more or less.

So how do you figure the power rating (I squared R) for a zerohm? :)

Moskog
01-28-2012, 09:02 AM
http://www.ebay.com/itm/ZERO-OHM-Resistors-Lot-50-0-0-Ohm-Jumper-BONUS-/230736589626?pt=LH_DefaultDomain_0&hash=item35b8f8f33a

Fifty zero ohm resistors costs ~$7. Sometimes less is more, more or less.



Could not resist, had to buy.
No my homemade pcb's will look more professional with resistors instead of all the jumpers, haha!

ajward
01-28-2012, 10:07 AM
Thanks for the explanations! The first time I saw one of them was a wtf moment!

@

Mark_T
01-28-2012, 01:23 PM
Anybody else ever been told how "0-ohm resistors" (one band, black) were devised because "jumpers" as such weren't allowed on old mil-spec pcb's?
[Jumper = No; 0Ω resistor = OK ]

That makes sense - in a high-vibration environment jumper links will work loose and fall off...

ElectricAye
01-28-2012, 04:27 PM
...

Fifty zero ohm resistors costs ~$7. ....

So how do you figure the power rating (I squared R) for a zerohm? :)

That's simple. You equate Power to dollars per ohm.

RDL2004
01-29-2012, 02:14 PM
That makes sense - in a high-vibration environment jumper links will work loose and fall off...

I'm just curious, how does this work? Other than the small blob of plastic in the middle, there doesn't seem to be any difference between a jumper and a zero ohm resistor.

skylight
01-29-2012, 02:21 PM
The reason for including them in a PCB layout is that they can be installed, when appropriate, with a pick-and-place machine.
Do they fit ok? I was led to believe that they are......a little short.

Sorry i'll get my coat.

Martin_H
01-29-2012, 03:19 PM
I'm just curious, how does this work? Other than the small blob of plastic in the middle, there doesn't seem to be any difference between a jumper and a zero ohm resistor.

I am tempted to sacrifice one of them for science to see what is inside. My guess is that the wire goes straight through and the plastic is window dressing around it. I like the idea of using these as jumpers to avoid short against a trace as that has happened to me.

doggiedoc
01-29-2012, 03:43 PM
Do they fit ok? I was led to believe that they are......a little short.

Sorry i'll get my coat.I found that to be humorous.

PJ Allen
01-29-2012, 03:56 PM
I like the idea of using these as jumpers to avoid short against a trace as that has happened to me.
The alternative, assuming a piece of solid wire, is to cut a piece of nylon tubing or stripped insulation.
Or, take the time to cut and strip the wire precisely. A lead forming tool (http://evilmadscience.com/productsmenu/partsmenu/68-bender) is inexpensive enough and can aid the process.