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LandymanStefan



Member Since: 30 Aug 2017
Location: Surrey
Posts: 860

England 2001 Defender 90 Td5 SW Epsom Green
Electrical circuit question - Diodes
I currently have an uproar 4x4 worklight on the back of my car with two switched ground wires coming off it. One in the boot so i can turn it on and off from there and one to the dash with a switch.

I want to add a second light with the same setup but dont want to run a second wire to the dash, everything from the first light is nice and neat and id reather not run a twin cable down (but will if i have to)

Ideally i want to share the ground that runs to the dash for both lights and then individual swithes for each light in the boot. Only problem i could see if i did that is both lights would turn on regarless of what switch was turned on in the boot am i correct in thinking i can isolate each light would be with a diode?

2 of these https://www.ebay.co.uk/itm/Durite-0-834-10...SwCuBcc6oP

I drew a picture pretending i know anything about electronics...
Would this work?



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Post #889183 5th Mar 2021 9:02am
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LandRoverAnorak



Member Since: 17 Jul 2011
Location: Surrey
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United Kingdom 2013 Defender 110 Puma 2.2 USW Orkney Grey
That won't work I'm afraid - you'll still turn both lights on. How would the dash switch 'know' which light you're trying to turn on?

The only way to use a single switch to turn on two independent things is if it has two pathways within it, i.e. an ON-OFF-ON changeover switch, or perhaps a rotary switch Darren

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Post #889193 5th Mar 2021 9:55am
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Dinnu



Member Since: 24 Dec 2019
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Malta 2012 Defender 90 Puma 2.2 CSW Santorini Black
As the circuit is. the dash switch will power both lights.
But the boot switches will power up the individual light, work switch for work light and bar switch for light bar.

If you want to control the lights independently from the dash, I am afraid you need to run 2 separate grounds, and 2 switches on dash. 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing
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Post #889213 5th Mar 2021 11:29am
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LandymanStefan



Member Since: 30 Aug 2017
Location: Surrey
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England 2001 Defender 90 Td5 SW Epsom Green
Ah I didn’t make myself clear. I want the switch on the dash to turn on both lights together. Then the two switches in the boot to switch the light individually.
Post #889220 5th Mar 2021 11:59am
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rallysteve



Member Since: 10 Feb 2014
Location: South Yorks
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United Kingdom 2002 Defender 110 Td5 DCPU Keswick Green
Think the OP is saying that he is happy with the dash switch operating both lights but wants them individually switchable in the boot. If so, i would recommend just using two-way switches in the boot for each lamp rather than diodes which will get hot and also drop upto 1v over each:


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Post #889221 5th Mar 2021 12:00pm
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LandRoverAnorak



Member Since: 17 Jul 2011
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Ah! I see what you mean now. Steve's solution is ideal Very Happy Darren

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Post #889222 5th Mar 2021 12:05pm
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custom90



Member Since: 21 Jan 2010
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I would prefer switches too, the only practical solution I’ve used Diodes for is in the live line on HD relays coils to prevent fly back voltage upstream back to sensitive power supplies.
Although very very small there is some voltage leakage and as mentioned voltage drop as well. Diesels Lives Matter. ⛽️🛢️👨‍🔧🧰⚙️
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Post #889230 5th Mar 2021 12:43pm
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rallysteve



Member Since: 10 Feb 2014
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United Kingdom 2002 Defender 110 Td5 DCPU Keswick Green
I have used diodes a few times but they should only really be used for creating 'logic' functions with very low power draw circuits (e.g. relay triggering).

I have used them:
- On old car alarm installations to isolate Left and Right hand indicators when the alarm only provides a single output (although this is a higher power use, it is only short duration and flashing),
- To create a single positive feed from both of my batteries which allows the contactor which connects them together to be closed if either of the batteries is not present or totally flat,
- In a 2 speed cooling fan circuit which changes two fans from series to parallel to vary the speed.

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Post #889233 5th Mar 2021 1:06pm
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LandymanStefan



Member Since: 30 Aug 2017
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Looks like a neat solution Steve Thumbs Up
Great idea
Post #889236 5th Mar 2021 1:18pm
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LandymanStefan



Member Since: 30 Aug 2017
Location: Surrey
Posts: 860

England 2001 Defender 90 Td5 SW Epsom Green
All good folks Thumbs Up





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Post #891101 13th Mar 2021 1:34pm
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