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 Posted: Dec 01, 2007 - 04:19 PM |
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Joined: Jan 17, 2007
Posts: 91
Location: Bellevue, NE
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Ok, so I know I am new at the hardware side of things but this one makes NO sense to me.
A buddy of mine at work insisted that they make 0 ohm resistors. I said "Of course they do. It is called wire and in comes in many sizes and colors." Then he pulls out the digikey catalog and shows me! He didn't know why and I can see why someone would spend almost a dollar on a 50mm length of wire when you can buy a 30m spool of 22 gauge for $15.
http://dkc3.digikey.com/PDF/T073/P1678.pdf
There has to be a reason someone would go the the expense of manufacturing these things. What am I missing?
I don't mind loosing beer bets (as I did on this) but there is NO WAY an entire industry is conspiring against me. |
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You can have my mac when you pry my cold dead fingers off of it.
Kevin McEnhill -- mcenhillk@gmail.com
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Posted: Dec 01, 2007 - 04:40 PM |
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Joined: Nov 01, 2005
Posts: 6326
Location: Hilversum - the Netherlands
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Since 0 Ohm resistors look the same as its resistive brothers, it can be treated the same way in f.i. automatic insertion machines for PCB-manufacturing.
In SMT they are commonly used to let tracks on one side of the PCB cross: the second track goes between the 2 pads of the smd-resistor of 0 Ohm
Third reason is to use them as configuration resistors. (Have a look at the schematic of the Butterfly: you'll find several of these 0 Ohm resistors)
So yes, you'll have to buy him a beer. Cheers !
Nard |
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Posted: Dec 01, 2007 - 05:00 PM |
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Joined: Apr 25, 2006
Posts: 2299
Location: Germany
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This reminds me on a tube I once saw in a tube-museum.
They had lots of diodes,triodes, tetrodes,pentodes and
so on, but the exhibition also showed a Nullode, a
tube with NULL (=zero) electrodes. I think I was
disturbed the same way you have been about 0-Ohm
resistors.
But there is an explanation. As often, Google knows
the answer also ! |
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Posted: Dec 01, 2007 - 08:25 PM |
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Joined: May 30, 2004
Posts: 8118
Location: Cincinnati, Ohio
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Well, consider that you have a PCB with options. Say you remove or add options. The "Zero Ohm " may be used to enable an input that would otherwise be inhibited, with out the "Zero Ohm " resistor to pull that input to VCC or GND.
In my serial backpack, I use "Zero Ohm " resistors s jumpers to set the BAUD rate to 115.2K BAUD as the default when it is shipped. If the end user wants one of the other three available BAUD rate, one or both of the "Zero Ohm " jumpers are removed. The internal pull up resistors take care of the reset.
It so happens that I primarily make single sided PCBs for most of my projects. "Zero Ohm " resistors are great for use as jumpers, eliminating the need to drill holes and insert "Thru-Hole " jumpers.
Handy devices, they are - "Zero Ohm " resistors...
Also, several months ago, there was a thread where, the exact same question about "Zero Ohm " resistors was asked. You might do a forum search or Google search and see what turns up. |
_________________
Carl W. Livingston, KC5OTL
microcarl@roadrunner.com
"There are only two ways to sleep well at night... be ignorant or be prepared."
The original Dragon Slayer !
Long live the AVR!!!
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Posted: Dec 01, 2007 - 09:48 PM |
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Joined: Apr 01, 2004
Posts: 3812
Location: New Mexico
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microcarl wrote:
In my serial backpack, I use "Zero Ohm " resistors s jumpers to set the BAUD rate to 115.2K BAUD as the default when it is shipped. If the end user wants one of the other three available BAUD rate, one or both of the "Zero Ohm " jumpers are removed. The internal pull up resistors take care of the reset.
That works very well in your serial backpack. I've been greatly enjoying the serial backpacks I got from you and am preparing to soon post a review of your fine project. |
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Kevin Rosenberg
http://b9.com
http://kevin.hypershots.com
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Posted: Dec 02, 2007 - 05:27 AM |
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Joined: Oct 26, 2006
Posts: 744
Location: Vancouver, BC, Canada
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We use lots of 0 Ohm resistors in our prototype cel phone designs at work. Since things are in the early prototype phase, there's often several possible configurations. Since it's very expensive to set up and run a PCB build, 0 Ohms are often placed around to allow for multiple configurations. Connect something one way and if you want to test the other way, populate a few and remove a few and you have the other configuration.
Don't worry, though, caught me by surprise a bit when I first saw them, too =) |
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Clancy
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Posted: Dec 03, 2007 - 05:09 PM |
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Joined: Mar 01, 2005
Posts: 91
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Yeah, it seems to me that they would just be used in cases where it's impracticable or undesirable to solder a jumper wire when you can cross a PCB route with an SMD device (that can be used by an auto-pickup and batch soldered.)
If there's 0-ohm thru-hole versions though, that would not make much sense to me... |
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Posted: Dec 03, 2007 - 05:13 PM |
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Joined: Nov 01, 2005
Posts: 6326
Location: Hilversum - the Netherlands
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Quote:
If there's 0-ohm thru-hole versions though, that would not make much sense to me...
See my first post in this thread  |
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Dragon broken ? Or problems with the Parallel Port Programmer ? Scroll down on my projects-page http://www.aplomb.nl/TechStuff/TechStuff.html for tips
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Posted: Dec 03, 2007 - 05:32 PM |
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Joined: Mar 01, 2005
Posts: 91
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Yep.
And clpalmer beat me to the other thing I was going to say too, so yeah, I got to this thread way too late. |
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Posted: Dec 03, 2007 - 09:23 PM |
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Joined: May 30, 2004
Posts: 8118
Location: Cincinnati, Ohio
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Psychlow wrote:
If there's 0-ohm thru-hole versions though, that would not make much sense to me...
Then you haven't done much PCB layout using thru-hole components. If making single sided PCBs, thru-hole "Zero Onm " resistors are essential - especially when the PCB is stuffed via "Auto Insertion " equipment. |
_________________
Carl W. Livingston, KC5OTL
microcarl@roadrunner.com
"There are only two ways to sleep well at night... be ignorant or be prepared."
The original Dragon Slayer !
Long live the AVR!!!
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Posted: Dec 03, 2007 - 10:31 PM |
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Joined: Apr 20, 2007
Posts: 6091
Location: Long Island New York
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Incidentally, zero-ohm resistors are anything but. I remembera buddy of mine used one in a pinch to create a low current ammeter. I must say it worked rather well too.
Jim |
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Jim
I have decided that I am no longer going to plan anything in advance. In a court of law this is called Pre-Meditated, and does not look good for the defense.....
Timer function not working properly? Check CLKDIV8 Fuse first 
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Posted: Dec 03, 2007 - 10:47 PM |
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Joined: May 30, 2004
Posts: 8118
Location: Cincinnati, Ohio
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jgmdesign wrote:
Incidentally, zero-ohm resistors are anything but. I remembera buddy of mine used one in a pinch to create a low current ammeter. I must say it worked rather well too.
Jim
Very true! They can range from a few milli-Ohms to nearly an 1ohm. But they aren't tested for any particular range of values, though... |
_________________
Carl W. Livingston, KC5OTL
microcarl@roadrunner.com
"There are only two ways to sleep well at night... be ignorant or be prepared."
The original Dragon Slayer !
Long live the AVR!!!
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Posted: Dec 04, 2007 - 03:11 PM |
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Joined: Mar 01, 2005
Posts: 91
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microcarl wrote:
Then you haven't done much PCB layout using thru-hole components. If making single sided PCBs, thru-hole "Zero Onm " resistors are essential - especially when the PCB is stuffed via "Auto Insertion " equipment.
I've done plenty of single-sided PCBs, but always home made and no auto-insertion equipment.
I'm not understanding something key, I guess - Why can't the equipment just be set up to insert a length of jumper wire? |
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Posted: Dec 04, 2007 - 04:12 PM |
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Joined: Nov 01, 2005
Posts: 6326
Location: Hilversum - the Netherlands
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See the picture for how resistors get fed into the automatic insertion machine.
It takes one tool for all resistors of a certain wattage and such.
For wire-bridges, a special tool would be required to handle those: so ONE tool for ONE specific component. See the cost-issue ? And extra labour it would take ?
And for that same reason, packages of IC's are standarized.
Nard |
_________________
Dragon broken ? Or problems with the Parallel Port Programmer ? Scroll down on my projects-page http://www.aplomb.nl/TechStuff/TechStuff.html for tips
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Posted: Dec 04, 2007 - 05:10 PM |
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Joined: Mar 01, 2005
Posts: 91
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That does make sense. The automatic insertion machines I've seen have been able to insert these though:
Just depends on the machine then, I suppose. |
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Posted: Dec 04, 2007 - 06:47 PM |
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Joined: Apr 20, 2007
Posts: 6091
Location: Long Island New York
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| I think you took that from your toy tank. Now, go put it back. |
_________________
Jim
I have decided that I am no longer going to plan anything in advance. In a court of law this is called Pre-Meditated, and does not look good for the defense.....
Timer function not working properly? Check CLKDIV8 Fuse first
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Posted: Dec 05, 2007 - 02:12 PM |
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Joined: Dec 17, 2002
Posts: 260
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| They also make DED's or Dark Emitting Diodes. |
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Posted: Dec 05, 2007 - 04:21 PM |
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Joined: Oct 17, 2003
Posts: 311
Location: Germany
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Posted: Dec 05, 2007 - 04:54 PM |
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Joined: Sep 20, 2003
Posts: 4080
Location: Surrey, England
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jgmdesign wrote:
Incidentally, zero-ohm resistors are anything but. I remembera buddy of mine used one in a pinch to create a low current ammeter. I must say it worked rather well too.
Jim
It probably depends on the tolerance. I always pay that little bit extra for 1% 0 Ohm resistors.
[Edit]Although, strangely, they always seem to be over 0 Ohms, I've hardly ever had one that's under...[/Edit] |
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Posted: Dec 05, 2007 - 07:03 PM |
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Joined: Mar 27, 2002
Posts: 18599
Location: Lund, Sweden
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| Mr John A Brown! After a realy shitty day you saved it all with your post! Still laughing! |
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