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discoBizz
Member Since: 20 Sep 2008
Location: Here...
Posts: 1220
  
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| Dual powering an accessory? |
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...in my case the reversing camera.
I would like the reversing camera to be powered either by reverse gear being selected (current setup) or by a switch independently. Am I right in thinking a switching relay is all that is required as below to choose between power sources and not fry the camera? (the switch will be between contact 87a and the camera)
TIA  ==> Guide - Inexpensive AV Modification
==> Guide - Extend the multimedia of your Discovery III (September 2011, v1.2 uploaded)
Last edited by discoBizz on Sat Aug 28 2010 9:45am. Edited 1 time in total
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 Sat Aug 28 2010 6:55am |
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discoBizz
Member Since: 20 Sep 2008
Location: Here...
Posts: 1220
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Thanks Si
I've got multiple cams in mind as well (currently trying to find a suitable front facing one to mount in the bumper) and have already gone down the route blue meanie paved with regards to a 4 port CCTV switching unit (does PIP as well).
All other cameras will be switched on (including the CCTV unit) from a switch in the custom electrical panel I'm currently building for the boot (inspired by the great Mr Wiggs  ), but I want to maintain the ability for the reversing one only to come live when I reverse.
Having read as mush as I could about relays, I think this should work, but I'm no expert hence the need for confirmation from someone more knowledgeable 
For less than £2 it should be a worthwhile enhancement me thinks  ==> Guide - Inexpensive AV Modification
==> Guide - Extend the multimedia of your Discovery III (September 2011, v1.2 uploaded)
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| Sat Aug 28 2010 9:10am |
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anglefire
Member Since: 09 Mar 2010
Location: West Midlands
Posts: 987
 
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Unless I'm reading the diagram completely wrong, the way its set up now, the camera will be permanently fed.
It is either fed from 30 to 87a (No power from the reversing camera switching circuit on 86), or when the reversing camera switching feed is live, via 30 to 87.
What you need to do (Well one way) is have a second relay, which takes either a switched feed from your manual switch or the switched feed from the reversing camera feed.
The other way, is to just take the link from 87 to 87a and add an override switch in parallel with the reversing to pull this relay in when you operate the override switch.
However, this will probably back feed into the reversing light circuit - so two relays would be needed, or just a changeover switch - I can't believe the power requirement is high.
If you need some sort of wiring diagram, I can knock one up, but it won't be until later today! Mark.
2006, D3 SE Auto Zermatt Silver. GNVP Sump Guard, RAI, Chrome Side Tubes,GNVP Sliders,Heated seats F&R, Heated screen, 4x4 Sat Nav enabled. ATR's (Thanks Ken)
Trailer called "Tilly"; Caravan called "The Van"
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Disco Picture Website Here
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| Sat Aug 28 2010 9:25am |
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discoBizz
Member Since: 20 Sep 2008
Location: Here...
Posts: 1220
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Thanks Mark
Biz wrote:(the switch will be between contact 87a and the camera)
Will this not do the trick? Admittedly I should add it to the diagram for clarity 
(edit: diagram updated! - the way I think is when not in reverse, contact with 87a allows current to the switch which then feeds the camera if needed; when in reverse, contact moves to 87 from 87a powering the camera regardless of the switch state - am I missing something?) ==> Guide - Inexpensive AV Modification
==> Guide - Extend the multimedia of your Discovery III (September 2011, v1.2 uploaded)
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| Sat Aug 28 2010 9:39am |
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anglefire
Member Since: 09 Mar 2010
Location: West Midlands
Posts: 987
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Yep, that will work
(And I did miss the written word first time  ) Mark.
2006, D3 SE Auto Zermatt Silver. GNVP Sump Guard, RAI, Chrome Side Tubes,GNVP Sliders,Heated seats F&R, Heated screen, 4x4 Sat Nav enabled. ATR's (Thanks Ken)
Trailer called "Tilly"; Caravan called "The Van"
_________________________________________________
Disco Picture Website Here
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| Sat Aug 28 2010 3:25pm |
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kernowexpeditionaryforce
Member Since: 15 Jan 2009
Location: Kernow
Posts: 314
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two 3amp diodes would be easier - twist both bandsides together and connect to camera positive, the the two remaining diode legs provide two positive turn-on inputs, one for reverse, the other from a switch
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| Sat Aug 28 2010 5:06pm |
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anglefire
Member Since: 09 Mar 2010
Location: West Midlands
Posts: 987
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Call me old fashioned, but I like relays
And if the OP already has a relay, then its a no-brainer! Mark.
2006, D3 SE Auto Zermatt Silver. GNVP Sump Guard, RAI, Chrome Side Tubes,GNVP Sliders,Heated seats F&R, Heated screen, 4x4 Sat Nav enabled. ATR's (Thanks Ken)
Trailer called "Tilly"; Caravan called "The Van"
_________________________________________________
Disco Picture Website Here
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| Sat Aug 28 2010 8:10pm |
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blue meanie
Member Since: 04 Aug 2005
Location: Berkshire - the western bit
Posts: 4989
 
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all looks very good Biz but switching the power for the reverse cam from two different sources seems overkill to me, all I did was make the power to all the cams on mine live when the GVIF box is on and then use 'Y' phono splitters to make the reverse cam output available for times other than when reverse is selected?
Si, you can switch between the two cams with a £3 switch and a £5 dual phono extension lead ( as long as you don't ever want to use it as an extension again that is )  no point in complaining.....
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| Sat Aug 28 2010 8:56pm |
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discoBizz
Member Since: 20 Sep 2008
Location: Here...
Posts: 1220
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Many thanks all!
It looks like I'll go with the relay as originally planned.
Re: dual powering itself, it may be an overkill, but my thinking is that the other cams and switch will rarelly be used continuously and all will be on/off by a single switch; while I know the amp draw is minimal, I thought I'd keep it as low as pos when not in use
Waiting for the last remaining bits to arrive and will get on with wiring, threadig etc! Will keep you posted!
Thanks again ==> Guide - Inexpensive AV Modification
==> Guide - Extend the multimedia of your Discovery III (September 2011, v1.2 uploaded)
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| Sun Aug 29 2010 5:05am |
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drivesafe
Member Since: 23 Feb 2006
Location: Gold Coast, Australia
Posts: 489
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Hi Niko, Just reverse your wiring on your relay.
That’s a changeover type relay and pin 87a is connected to pin 30 when the relay is off.
Connect your camera power supply to 30, via a suitable fuse.
Connect 87 to an +12v supply.
Connect 87a to your manual switch.
If your not in reverse, your switch can operate the camera but if you select reverse, whether your witch is on or off, the relay will disconnect your switch and pickup the 12v supply. 2008 TDV8 RR Lux + 2009 D4 2.7
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| Sun Aug 29 2010 7:06pm |
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CarlW
Member Since: 07 Aug 2005
Location: Lanarkshire
Posts: 41
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Hi,
I expect the camera only requires 20-200mA so even simpler would be two diodes one from the reverse light supply and one from the switch supply - the camera would then be supplied from either, there would be a small vold drop of perhaps 0.6v but given the high voltage on the disco you'll still have well over 12v at the camera
Carl TDV8 RRS in Java Black - sorry I've defected
Focus TDCi Titanium
BMW R1150GS
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| Sun Aug 29 2010 7:36pm |
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discoBizz
Member Since: 20 Sep 2008
Location: Here...
Posts: 1220
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drivesafe wrote:Hi Niko, Just reverse your wiring on your relay.
Thanks Tim, a little confused though  , why reverse the wiring?
Fused power input is on pin 30, pin 87a provides that to the switch (to turn on/off at will), unless in reverse (trigger on pins 85 and 86), in which case relay opens and makes contact with pin 87, feeding power directly from the fused pin 30...
I think this is how it should be, no? ==> Guide - Inexpensive AV Modification
==> Guide - Extend the multimedia of your Discovery III (September 2011, v1.2 uploaded)
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| Mon Aug 30 2010 5:52am |
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drivesafe
Member Since: 23 Feb 2006
Location: Gold Coast, Australia
Posts: 489
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Hi Niko, and leave it as you have it.
I didn’t take into account that the way you had positioned the switch that it was still to be connected to the wire coming from pin 87.
It was a little too early in the morning for me. 2008 TDV8 RR Lux + 2009 D4 2.7
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| Mon Aug 30 2010 8:30am |
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know the feeling Tim, caffeine often takes a while to come into effect for me most mornings!
