oliwb
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| posted on 7/1/06 at 06:40 PM |
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Shielding stuff....
Hi, got me megajolt and started wiring it, but whats the deal with interference and shielded cables.....I've just used a combination of Maplin
and halfords standard cable.....Now I know I'm a bit dense when it comes to wiring but please don't tell me I need new wiring and have to
do it all over again! Cheers Oli.
If your not living life on the edge you're taking up too much room!
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Daxrushv6
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| posted on 7/1/06 at 07:09 PM |
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On my DTA instructions it said to use shielded cable for the crank sensor and to use normal auto cable for the rest and for the sensors to twist the
cables together, as in twisted pair.
Not sure what you have but if you use shielded cables remember to only earth the shield at one end.
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stevec
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| posted on 7/1/06 at 07:14 PM |
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Its a good idea to keep signal cables as far as possible from high current cables such as starter motor cable.You can get false trigger signals as the
engine cranks.
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MkIndy7
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| posted on 7/1/06 at 08:03 PM |
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Looking at the picture of the blue wire, have you just taped up the shielding/brading?
I thought u were supposed to earth this at both ends?
I'm sure thats how it was on the shielding for the pip and saw lines on the ford EDIS,
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oliwb
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| posted on 7/1/06 at 08:09 PM |
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anyone know how these shielding cables actually work??? Looks like I'm gonna have to re-do a lot of it! Thanks....Oli.
If your not living life on the edge you're taking up too much room!
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flyingkiwi
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| posted on 7/1/06 at 09:35 PM |
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If my memory is still ok, I think the shielding works by dissipating any induced current into the wire, preventing the main core from getting exposed.
Similar effect on TV cable too, which prevents stray RF signals from interferring.
IIRC if two wires run near each other one can induce a current into the other if the current/voltage is high enough.
Hence why the RAF/RN are spending a hell of a lot of money at the mo changing all the armament circuits to tri shielded wire on the GR7 upgrade.
It Runs!!!!! Bring on the SVA!
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paulf
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| posted on 7/1/06 at 10:52 PM |
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Oli
You need to use shielded wire for the cranksensor to edis and the SAW and PiP wires from edis to megajolt. If you look at the wiring on the edis plug
you will note this is shielded on these connections.I found some fiestas have the crank sensor wiring from front of the engine to the inner wing via
chassis rail and front cross member and it is plenty long enough to use on a seven from sensor to megajolt under scuttle.
You need to earth all shields at one end only in this case at the Edis unit.Also feed the megajolt from the edis live supply via an inline fuse of
about 1amp.
Contact me if you require anymore info.
Paul.
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MkIndy7
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| posted on 7/1/06 at 11:18 PM |
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Not sure if it matters or defeats the object but as you can't see whats going on with the shielding at the crank sencor end, I connected the
braiding at the crank end to a spare core and then to the same earth at the EDIS end
We used something like this:
http://www.maplin.co.uk/Module.aspx?TabID=1&ModuleNo=230&doy=7m1
(think you'd only need the 4 core at 99p/m)
I happened to find at work, its used on control circuits for detectors and actuators etc on large commercial heating systems(shops, factorys,
wharehouses, offices etc).
There's usually loads lying around above cielings that contractors have left, or keep an eye out when there clearing site
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Mix
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| posted on 8/1/06 at 09:12 AM |
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I'm not 100% sure here so feel free to correct me , but shouldn't sheilding only be grounded at one end to prevent the possibilty of
ground loops?
Mick
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Bob C
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| posted on 8/1/06 at 08:59 PM |
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Shielding is one of those 'black art' things that you get used to after years of experience. Any EMC advice agent will say ground the
shielding at bOTH ends - but this can be problematic in a car - it's all to easy for an unrelated fault to divert the starter motor current
though the shielding & make a right mess.
A car is generally not so bad a place for interference, being a metal box without AC supplies!!
cheers
Bob
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paulf
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| posted on 8/1/06 at 09:21 PM |
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Thats generally correct, and on the donor Fords the sheilds are all earthed at the Edis mounting point only.
As Bob c says it is more important when in an ac enviroment where the sheild could actually act as a inductive loop and pick up stray current in the
circuit if made into a loop by earthing both ends.
The crank sensor wiring is best done using the cable and plug from a donor car .
Paul.
quote:
Originally posted by Mix
I'm not 100% sure here so feel free to correct me , but shouldn't sheilding only be grounded at one end to prevent the possibilty of
ground loops?
Mick
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02GF74
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| posted on 9/1/06 at 11:26 AM |
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quote:
Originally posted by flyingkiwi
IIRC if two wires run near each other one can induce a current into the other if the current/voltage is high enough.
you can reduce the effect by routing the wires far apart and if they have to cross, then they do this at right angles. running them parallel is
bad.
Ground at one end as said.
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