0 ohm Resistor wattage

I have a 0 ohm resistor in series with the +5V power supply (as a provision to disconnect, if not needed). The power drawn by the connected circuit is 1A through this 0 ohm resistor. What should be the wattage of this resistor? Since there is no voltage drop across this resistor, can it be 0.1W or 5V * 1A = 5W? I am new to this stuff and hoping to get help from this great forum.

-Mark

Reply to
Mark
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There is no such thing as a zero ohm resistor. Even a small piece of wire has some resistance.

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I'm never going to grow up.
Reply to
PeterD

Sure there is such a thing as a zero ohm resistor.....

To the OP, look up the data sheet for the part you are using, see what the maximum current is.

Reply to
Dennis

The zero ohm resistors i've seen have just been resistor size encapsulation around straight through lead wire. Usually used for pcb links. Don't know about smd parts, but you could verify capability using a bench supply in current mode, in the absence of other data...

Regards,

Chris

Reply to
ChrisQ

A more interesting question is what is the tolerance? Farnell do a nice range of 1% ones. There are some 5% ones too but it is a false economy IMO.

To the OP: Look at the datasheet for the current rating but it is a pretty poor "zero ohm" resistor that can't take 1A.

--

John Devereux
Reply to
John Devereux

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Thanks for the responses. As Chris said the 0 ohm resistor is for pcb link and it is an SMD resistor of 0603 size. Assuming it is of 0.1 ohms and 0.1Watt for this discussion, it will allow more than 1A (5/0.1) current that is required by the circuit after this 0 ohm resistor but is the wattage OK?

-Mark

Reply to
Mark

Ohms law ?.

Best thing to do would be to measure the actual value with 4 wire, Kelvin clip ohm meter. 0.1 ohms sounds high for a real world part of that value. More like 0.01 ohms or less...

Regards,

Chris

Reply to
ChrisQ

A 0r resistor will probably have milliohms of actual resistance; the datasheet should say so. 1 amp shouldn't cause significant voltage drop, or heating, in any reasonable part, like an 0603 for example.

John

Reply to
John Larkin

The designation 'zero ohm' is hyperbole. It's a piece of wire, and it has resistance. If it's any good at all, it also has a current rating in its data sheet, and maybe even some comments on whether that current rating can be matched by the solder joint holding it onto the board.

I would assume that if the thing were no narrower than the traces that can safely carry 1A on the board then you're OK -- but I'd still dig out the data sheet in a spare moment, to be sure.

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Reply to
Tim Wescott

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Yes, even copper traces have current limits.

For 20m ohm jumper:

0201 1A 0402 1.5A 0603 2A 0805 2.5A 1206 3.5A 1210 5A 1218 7A
Reply to
linnix

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The 5% units are invaluable--you can cherry pick the -5% units, gleaning parts critical for use in FTL transmitters, flux capacitors, perpetual motion machines, etc.

-- Cheers, James Arthur

Reply to
dagmargoodboat

Why not look at the data sheet?

For example a Panasonic 0603 "zero" ohm resistor (they refer to it as a "jumper" in the data sheet) is rated for 1A.

kevin

Reply to
kevin93

I think you missed my point, that everything has resistance. In this case the jumper wire (which is what a 'zero ohm' resistor is) would have resistance, and given enough current it would overheat.

--
I'm never going to grow up.
Reply to
PeterD

I didn't miss you point, in the context used, "zero" means zero nominal resistance.

Reply to
Dennis

Bingo! Correct answer. There are zero ohm SMD resistors made so that pick and place machines can install them. Google found this:

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What you are looking for is the max current rating, not necessarily the wattage (since dissipation will not be well defined for zero ohms).

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Paul Hovnanian  paul@hovnanian.com
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Reply to
Paul Hovnanian P.E.

What you are looking for is the same size as that non-zero Ohm resistor you might put into the same place instead of zero Ohm. I wouldn't bet my tooth for it but, IMHO, current rating of e.g. 0603 zero Ohm resistor way exceeds that of PCB traces you can put it across...

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Reply to
Sergey Kubushyn

The resistance of the solder joints may be higher than the SMD zero ohm resistor.

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Teflon coated.
Reply to
Michael A. Terrell

Wire, etc has resistance - INCLUDING connectors and vias! Maybe in the region of 0.1 ohm. At a measly one amp, it is the current handling capability of the wire, etc that you must be concerned with.

Reply to
Robert Baer

Vishay data here:

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Reply to
Dennis

I like that idea. -5% of 0 ohm could be very handy to have :-)

Reply to
Pimpom

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