JekRankin
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| posted on 13/5/12 at 05:03 PM |
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Very basic wiring question! Relays -switched live or switched earth? Also - Hazards!
Sorry in advance for the very basic question -
I'm tacking my dash wiring just now and am considering the placement of my relays and switches. Are there any advantages or disadvantages in
placing a switch on the earth side of a relay, as opposed to switching the +12v feed?
Cheers,
Jek
[Edited on 13/5/12 by JekRankin]
[Edited on 13/5/12 by JekRankin]
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big_wasa
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| posted on 13/5/12 at 05:23 PM |
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switching the earth is very common. Most ecu's switch the earth.
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gremlin1234
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| posted on 13/5/12 at 05:24 PM |
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switched negative is usually a bad way to do things.
however it is not uncommon for things like door switches, and horns to run in that manor.
also many battery cut-off switches isolate the battery negative from the chassis/body
edit:
also oil pressure lights, and good old 'points' ignition commonly switch to chassis,
[Edited on 13/5/12 by gremlin1234]
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JekRankin
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| posted on 13/5/12 at 05:55 PM |
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Thanks for the replies. Why is switching to earth less preferable? For most of my circuits, I have the option to switch either the earth or the
live.
Jek
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snowy2
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| posted on 13/5/12 at 06:03 PM |
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He is mistaken there is no difference in live or earthed switch the latter is more common these days.
sometimes you are the pigeon, most of the time the statue.
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JekRankin
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| posted on 13/5/12 at 06:13 PM |
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That's good to hear. Switching to earth would be my preference.
All my relays are mounted beside the fusebox, so I think it will be a bit neater if I loop a power feed to each, then have all the switchgear
switching to an earth by the steering column.
Jek
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avagolen
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| posted on 13/5/12 at 07:22 PM |
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Hi Jek,
As far as I am aware, switching the earth is the safer way to do it.
The reason is that if the 'long wire' to the switch gets damaged and shorts out, there will be no
burns / overheating / fuse blowing of the said wire as there is a relay coil in circuit.
This effectively only switches the cct on.
Rgds
Len.
The Answer for everything, but never the last word....
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stevebubs
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| posted on 13/5/12 at 07:28 PM |
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I wired my car with all the relays switched to earth. However, the relays were switching the the live feed for the circuits...
Hope that helps??
S
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JekRankin
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| posted on 13/5/12 at 07:59 PM |
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Hi Len, thanks for the info, that makes sense even with my terrible grasp of electrics! Switched earth it is! Hope the build is progressing well.
I think that I'll be doing the same as you describe Steve. The wiring pretty much makes sense to me now, except for one item - the hazards.
On that note......
I have two hot wire flashers, one for indicators and one for hazards. I also have an 'on-on' double pole switch
(link)
I've had a look about on here, and found a diagram which seems to suit the pieces I have. Just one problem - I don't understand
what's going on at the hazard switch! I've modified the diagram with numbers one to six on the hazard switch pins.
From what i understand of this type of switch, pin 3 is either connected to pin 1 or pin 5 depending on the switch position. Pin 4 is connected to
either 2 or 6. This can't be right though, since the circuit logic doesn't work with this configuration. Can anyone shed some light on the
switch logic, as I am quite lost?
Many thanks,
Jek
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I predict a Riot
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| posted on 13/5/12 at 08:56 PM |
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For your diagram to work your hazard switch needs to connect 3,4,5 and 6 together.
If it doesn't then either get a different switch or if you tell me the make of your switch I will draw you a new diagram.
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JekRankin
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| posted on 13/5/12 at 09:06 PM |
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Thanks! My switch is the following one here - I think I should be able to loop between the terminals to make it work like you suggest?
Link
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I predict a Riot
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| posted on 13/5/12 at 09:13 PM |
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There is no schematic on that link for the switch terminals. Test it out with a continuity meter if you have one. If it is a simple two pole, change
over type switch then adding links as you say will make it suitable for that diagram.
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JekRankin
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| posted on 13/5/12 at 09:16 PM |
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Ok thanks, I'll figure out the switch logic with a multimeter, and then I think I should be able to loop it to suit. I think it makes sense to
me now, but my brain does not like circuits!
Cheers,
Jek
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snowy2
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| posted on 14/5/12 at 07:57 AM |
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The switch shown in my drawing above is for the standard hazard switch 1+2 are connected in off and the others are connected when on. to use a
“normal“ switch look at this link
http://ollr.10.forumer.com/a/posts.php?topic=14038&start=0
i am at work so its hard for me to edit the link on my phone.
[Edited on 14/5/12 by snowy2]
sometimes you are the pigeon, most of the time the statue.
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