Led lights

[Melfi]

[quote=caprihorse;11689]Relay and fuses... that's basics... [/quote]

I didn't understand anything out of this thread... :022:

[caprihorse]

[quote=Melfi;11690]I didn't understand anything out of this thread... :022:[/quote]
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I know... :008:

[Desert Lizard]

[quote=caprihorse;11692]----------------------
I know... :008:[/quote]

I completely agree Capri

[CAMEL]

Got my HID lights wired from a auto electrician in Ajman, but not before visiting at least 4 of them....Need to make a judgment if the guy knows the Job.

Finally got it wired for AED 150.00 including Cut-out Relay fuse and connected it to the existing fog lamp switch in the car which was empty.

Correct wiring is very critical....

[Hamdan]

very good light i like it

[bu-hamdan]

[quote=Desert Lizard;11688] Moreover, the switch should also be good quality to handle the load (even with a relay) and what ever the electrician says,
Good luck[/quote]

Thank you almosters for sharing usfeul information in the forum.

DL...
As per my knowledge ..relays & fuses come in different amps or watts as per your requirements. However if you put good relay, the switch will never be overloaded. because the relay will take the load & distribute the required amps to the switch.

I put very small switch -because the big one looks ugly- which will take load of max. 15amps for 4 numbers of xenon fog lights. Each bulb of these is 55watt (total is 220)... moreover the air compressor.

I put also on top of the battery(I mean car battery) voltmeter fuse. It shows you battery volts or if there is any voltage drop. I showed it to Bu Salem last week.


Thanks for the useful information Bro.........

Regards,
Bu-Hamdan

[Desert Lizard]

[quote=bu-hamdan;11699]

However if you put good relay, the switch will never be overloaded. because the relay will take the load & distribute the required amps to the switch.

[/quote]

I don't think that my earlier post was clear because it wasn't specific. Here is the what should be done in practice (and in theory) This is not a full treatment of car wiring, maybe I will do that later with pictures and diagrams.

First of all, some definitions:
A relay is an electro-magentic switch. Which essentially means that this switch needs electric current to switch on and off. In a normal switch (at home or inside the car) we physically push a button so two wires are connected together and current flows. In a relay, when an electric current is supplied to the magnet terminals, the magnet activates and "closes" a separate circuit through the other terminals. (There are other types of relays that do the same thing without a magnet, just for your info)

A fuse is a piece of conductor designed to melt or break when the current passing through it exceeds a certain level. The material in the fuse heats up as current passes through it. As current increases, the heat increases until it melts. The circuit breaker at home does the same thing but through a different method.

Now for the relay use
When ever you turn your physical switch on a small current passes from the battery to the relay. The relay's magnet then activates and completes the circuit from the battery to the device (the LED/Fog Lights/Fan etc). When the relay is "closed" or On the lights draw power directly from the battery and turn on. This circuit has the higher current load since the device power rating is higher (204 watts in Duck Commander's case).

So we end up with two circuits: The first is made of a battery, a switch and a relay, (we'll call it Relay Circuit) and the second is made of the Battery, the relay and the Fog Lights (We'll call it Light Circuit). When the first circuit is closed, the second circuit is closed and the lights come on.

Now we know from Ohms law that the Light Circuit will draw about 17Amps from the battery (P = VxI, watts = volts x Amps, Amps=watts / volts and in numbers amps=204watts / 12 volts = 17). So how much will the Relay Circuit draw? The typical car relay would draw something like 0.15 amps, which is significantly less than the lights.

Therefore, using a relay allows us to control a relatively large current (17 amps) using a very small current (0.15 amps). It is much safer to use a relay because the current coming into the switch inside the car will not cause a fire (high current generates heat --because of resistance-- and may burn wires and switches) or electric shock (if you stick your finger where it shouldn't go).

Why use a Fuse
A fuse is supposed to sacrifice itself to protect both the wires, and the device you are powering. If for any reason (short, water melted wire etc) a higher current is drawn from the battery, the fuse will burn and disconnect. Then you simply fix the problem and replace the fuse. No damage to any other components.

A fuse MUST be placed between the battery's positive terminal AND the relay input that goes to the lights, because that is where the higher current flows. Most relays would go for 30/40 amps or higher.. so without a fuse the lights will fry if the current goes to 25 or 30 amps.

And if you have purchased a very nice and expensive switch, there is no reason why you shouldn't protect it with2.5 or 5 amps fuse. After all, most fuses cost only half a dirham.

So to finally respond to the comment on a "good relay protects the switch," I would say, these are two separate circuits. The relay isolates the switch from the main load, but the switch has its separate power source too.

I hope this post is clear somewhat!!!

[caprihorse]

Very good answer Professor DL. Pls allow me to add some more details.

Relay does not have a magnet, but a coil, when powered, produces magnetic field around. A definitions says: A relay is an electrically operated switch. Relays use an electromagnet to operate a switching mechanism mechanically.

Additionally it is important to use rated thickness of wires for calculated current, mainly in the secondary circuit, powering the lights. If it is under-estimated, the wire will act like a fuse and melt, with the sparking effect and may cause the fire.

The main fuse should be rated as 10% above the theoretical lights current consumption. E.g. one light rated 50W, gives total power consumption for 4 lights 200W. The current equals 16.6A, so the fuse should be 20A, as the fuses available on the market are in 5A increments. The wire thickness should be approx. 3 mm2. If you use thicker wire, it will not harm the installation.

To make the installation more clear (or more confusing), I'm attaching a simple image.

[IMG]http://www.classictruckshop.com/clubs/e ... oglite.jpg[/IMG]

[Darshan]

Good one Capri. I am sure a lot of people will benefit from the above post.

[Duck Commander]

Thanks DL and King of Capriland, Now I am becoming good newbie, and tonight I am going back to that electrician to F*** his A**