# What Relay do I want ?



## TEV (Nov 25, 2011)

Any automotive relay will work, regarding the fuse: do you intended to power the camera and the screen from the reversing light wire ? Or just the relay ? Usually the fuses are there to protect the wires in case of a short circuit (the fuse will blow so the wires won't melt and catch on fire) .

You will need to know the power ratings of your electric consumer (relay only, relay&camera, relay&camera&screen) size the wires regarding to that number and size the fuse regarding the size of the wires.

If you will only power the relay, a 5A fuse will be enough.


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## TEV (Nov 25, 2011)

The relay should be something like this :

http://www.ebay.com/itm/1x-12V-30-4...t=Car_Audio_Video&hash=item565a676c11&vxp=mtr


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## royclark (Aug 19, 2013)

TEV said:


> Any automotive relay will work, regarding the fuse: do you intended to power the camera and the screen from the reversing light wire ? Or just the relay ? Usually the fuses are there to protect the wires in case of a short circuit (the fuse will blow so the wires won't melt and catch on fire) .
> 
> You will need to know the power ratings of your electric consumer (relay only, relay&camera, relay&camera&screen) size the wires regarding to that number and size the fuse regarding the size of the wires.
> 
> If you will only power the relay, a 5A fuse will be enough.


Only powering the relay from the reversing wire so 5A fuse OK.

I will start off with a *5A* fuse to power the camera, transmitter & screen.
camera = Power consumption:300mA
Screen = Power consumption: ca. 6W
Transmitter = not known


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## TEV (Nov 25, 2011)

royclark said:


> Only powering the relay from the reversing wire so 5A fuse OK.
> 
> I will start off with a *5A* fuse to power the camera, transmitter & screen.
> camera = Power consumption:300mA
> ...


5A * 12W = 60W

300mA = 0.3A*12V= 3.6W

3.6W+6W=9.6W 

60W-9.6W=50.4W there is no chance for that transmitter to get even close to 50W.

In conclusion a 5A fuse should be enough for everything else too.

Have fun !


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## royclark (Aug 19, 2013)

TEV said:


> 5A * 12W = 60W
> 
> 300mA = 0.3A*12V= 3.6W
> 
> ...


Thank you very much for your help.


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## Ampster (Oct 6, 2012)

TEV said:


> 5A * 12W = 60W
> 
> 300mA = 0.3A*12V= 3.6W
> 
> ...


Isn't the reversing light wire already fused? Another on that leg would just add complexity.


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## royclark (Aug 19, 2013)

Ampster said:


> Isn't the reversing light wire already fused? Another on that leg would just add complexity.


The 5A fuse would be between the trigger (Rev light wire) and the relay.
_(I don't know what the rev lights are fused at.)_
So what you are saying is :- Don't put a fuse in this position ?

I will then put another 5A fuse between the power supply and the relay.

Am I correct ?


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## TEV (Nov 25, 2011)

royclark said:


> The 5A fuse would be between the trigger (Rev light wire) and the relay.
> _(I don't know what the rev lights are fused at.)_
> So what you are saying is :- Don't put a fuse in this position ?
> 
> ...


Hi is right , but having that fuse isn't really unnecessary because if you have a short circuit in the additional wiring you are installing you will burn the additional fuse (you have to make sure that the additional fuse is a lower rating than the fuse for the reversing light) so will not take out your reversing light. 

Whatever you install or not that fuse it's your decision, nothing rong will happened either way.


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## royclark (Aug 19, 2013)

TEV said:


> Hi is right , but having that fuse isn't really unnecessary because if you have a short circuit in the additional wiring you are installing you will burn the additional fuse (you have to make sure that the additional fuse is a lower rating than the fuse for the reversing light) so will not take out your reversing light.
> 
> Whatever you install or not that fuse it's your decision, nothing rong will happened either way.


 Thank you.
That's the way that I was thinking, but hey, I'm not an electrician, thats why I'm picking your brains.


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## royclark (Aug 19, 2013)

royclark said:


> I am fitting a reversing camera to my 2009 Audi A6 Avant.
> 
> My idea is to take a feed from the reversing light wire to power a relay.
> 
> ...


 









OK I have connected my relay to the reverse wire (trigger 3A fuse).
Then taken power from power socket with a 5A fuse.

Question :- (TOP PIC.) On the monitor wire it says to connect the blue wire to reverse light wire, do I connect this blue wire to the wireless receiver ?


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