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Author Topic: Stranded vs. Solid wire for digital communications  (Read 2108 times)
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nr Bundaberg, Australia
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I went to buy an HDMI cable the other day and the first one I found was $149, I nearly died but eventually found one for about $15. The screen looks just fine to me but I'm not very sophisticated in this field smiley

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Rob
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Rob Gray aka the GRAYnomad www.robgray.com

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One question nobody has thought to ask before now...

How are you connecting the ribbon cable?  Are you using connectors of some form?  If so, what are they?

Molex.
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Its all about the bacon...   smiley-wink


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Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   smiley-cool

Topsham, Vermont USA
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There's a Mouse born every second, and statistically about 50% of them will soon give Mouse Milk.

And somebody will buy it...
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Regards, Terry King terry@yourduino.com  - Check great prices, devices and Arduino-related boards at http://YourDuino.com
HOW-TO: http://ArduinoInfo.Info

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One question nobody has thought to ask before now...

How are you connecting the ribbon cable?  Are you using connectors of some form?  If so, what are they?

Molex.

Molex is a brand name.  They make rather a large number of connectors.  Which connectors are you using?
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Replacement for the Arduino IDE: UECIDE - Proper serial terminal, graphing facilities, plugins, overhauled internals.
Java isn't bad in itself, but it has enabled morons to write programs.

nw pa. uas
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stranded cabling for digital communication has to follow the same guidelines as solid for cat5 or cat 6
pairs must be twisted to prevent crosstalk
stranded is used more in industrial environments due to its ability to withstand both vibration and flexing
although the strands are smaller there is actually more total surface area to the conductor than there is with solid wire.
(electrons travel on the surface of a conductor not through its center)

if you are using an old ribbon cable you are getting crosstalk that is interfering with proper communication
crosstalk is a difficult thing to track
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Anaheim CA.
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At the speeds that SPI or I2C operate at on an Arduino, impedance's in/ out or cabling are not really a worry/issue. the problem Statistically is Much more likely to be a Power supply or By-passing issue. The cable capacitance lead to lead/ft will not likely exceed 50 pF, in comparison a .1 uf cap is 100000 pf. Much more likely in my experiences with my hardware to be a missing magic bullet or two or a wrong value pull-up. For 10" of wire on SPI or I2C you might try a 1K to 470 ohm pull-up. A 5 to 10 ma pull-up will do wonders to make cable capacitance go away. If you think it is capacitance or cross talk (I Don't but I've been there before) then null it out by doing two things in one, reduce the Pull up so as to force the processor pin to discharge/charge that capacitance faster/better and second lower the impedance with a parallel resistor (lower impedance - lower possible values of cross talk) use a lower value pull-up, Now you are drawing more current through the bus... great BY-PASS it to GROUND by installing a 100Uf cap on either end of any Vcc line AND at Least a 100 nF (.1uF) cap on either end of the Vcc wires as they come/go from bread/pc boards. The data passed in SPI or I2C is synchronous, ...   Clocked... What is cross talking??? other bus traffic??? You figured out how to do two things at once on an Arduino??
Pass on that secret, please...

Doc
« Last Edit: June 08, 2012, 10:09:33 pm by Docedison » Logged

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Arkansas, US
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This one is even better: $6700 for an AC POWER CORD!!!!

That counter-spiral technology must work wonders.

And this one has DUAL STAR-QUAD technology!  DUAL!!!
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Fantastic customer reviews!

I once had to interview a man for a senior post as head of the Power Supply group. I was asked to come in after about two hours into the interview to ask him some technical questions. On his CV he claimed he was the man who "invented" gold plated power connectors for Hi-Fi.
After a few initial technical questions, not related to this, he asked to be excused to go to the bathroom. He never returned, so I never got to ask him about it.
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nr Bundaberg, Australia
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$6700 for an AC POWER CORD!!!!
Man am I in the wrong game smiley-sad

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I never got to ask him about it.
Bummer, that would have been interesting.

______
Rob
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$6700 for an AC POWER CORD!!!!
Man am I in the wrong game smiley-sad

Rob

Kind of like the guy selling pencils for $5k each. When asked how many he expected to sell, the answer was just one would do.
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Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   smiley-cool

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stranded cabling for digital communication has to follow the same guidelines as solid for cat5 or cat 6
pairs must be twisted to prevent crosstalk

Not necessairly so. It depends on the particular situatrion. I now have my arduino ethernet shield connected to my router via 50' of non twisted cat3 four conductor phone wire connected in a 10baseT configuration. Seems to work ok. Also worked ok in the past with an old webcam pc too.
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Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   smiley-cool

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Randomized double-blind tests consistently show up HiFi "Golden ears" as charlatans.  If you show someone which hifi units are being used they consistently choose their favorites as sounding better, but without that information they can't tell the difference!   Its way easier to tell the difference in room-acoustics than to discriminate decent hifi units from one-another.

http://www.engadget.com/2008/03/03/audiophiles-cant-tell-the-difference-between-monster-cable-and/
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nr Bundaberg, Australia
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Coat hangers, that's priceless smiley

EDIT: If you follow MarkT's link click on the photo for the full story.

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Rob
« Last Edit: June 10, 2012, 05:54:40 pm by Graynomad » Logged

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I gave up in Gales of laughter when I had a "Senior Engineer" try to tell me with a perfectly straight face that he got a "Bargain" on Low Noise "Low Oxygen Content" copper wire. He felt that was the only was he was ever going to get truly low noise figures from his Pre-Amp. Got 'Summarily Dismissed" from that job... Not IMO a great loss. I saw the same 'concept?" being put forth for Audio Jumper cables. 15 - 20 years ago. I for a moment, thought too that I was in the wrong business too... But old and ugly as I am I still like what I see in the mirror. I don't think that would be so, did I follow that path.

Doc
 
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--> WA7EMS <--
“The solution of every problem is another problem.” -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

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