Outer Limits 4x4 Board

righto, i built a roof console, and i'm using the light beam as an anchorpoint,
i want to change the old light to 4 LEDS- each on an individual switch, branching from the old light wire

from my understanding, this is the setup needed-

1. positive wire crimped to 4 wires
2. each branch goes to an individual resistor
3. each resistor then goes to the switch
4. each switch then runs to its light
5. each light then runs back and gets crimped to the individual negative wire

am i right? if something seems amiss, please do tell, don't really wanna screw it up, and definately not up for melting the wire in the roof.... (console will not move for a very long time)

What sort of LED's are you using? Just a LED in its bare component form? or one of the LED things already built in a typical light holder (screw in or fuse kinda one)

If your just using individual LED's, then you are absolutely correct with your wiring. Resistor can be after the switch attached to the LED (often more convenient this way as you can heatshrink the resistor to the leg of the LED).

If you are using a pre-assembled LED Unit, they usually have the current limiting resistor inbuilt.

You are also aware that these lights will only work with your door open? (just making sure).

If you are using a LED individually, they generally do not give a very good spread of light.

why would it only work with the door open? the old light had the 3 features-
on off door

wouldn't it now be either on/off on/door off/door (depending on which wire i connect to where)

the LED's are individual, short leg long leg

chikoroll_ wrote:why would it only work with the door open? the old light had the 3 features-
on off door

wouldn't it now be either on/off on/door off/door (depending on which wire i connect to where)

the LED's are individual, short leg long leg

ah yeh your right sorry ^_^

The way most interior light's works is by having the positive voltage supply, and then switching the ground, either the door completes the ground, or if you goto the other mode of operation, you ground it that way.

So to keep this mode of operation you need to make sure the switches you buy for the LED's are DPST, and then you need to adjust your wiring.

DPST means dual pole single throw, or means a 2 position toggle switch. (one with 3 terminals)

i did a quick drawing to show you what you need.

http://members.optushome.com.au/warwick ... 20leds.bmp

lol did you not say "quick drawing" ...was that really "quick" to draw?

thanks for it

i will use that as a template for when i do wire it up

for some reason the door goes direct to the roof mount... so am i right in assuming i should just attach the door wire to that mount? (not too fussed on sending the roof live though) (or is that the dead connection and the wire is the door?)

Thats a great diagram. Just for a techo dummy . What value resistors do you use.

firestang wrote:Thats a great diagram. Just for a techo dummy . What value resistors do you use.

depends on the led used.

The LED will be rated for a certain current. Once you know the current and the voltage drop across the LED, you can then use this information to calculate the resistor value.

Typical value for a led would be about 10mA, typical voltage drop across a LED is about 1.6volts for a standard one, or about 1.9volts for a high brithness one.

So now we know the current through the circuit, and the voltage drop across the LED. The voltage drop across the resistor needs to be the rest of the 12v. So 12-1.6 = 10.4v

Use Ohms law, V = I * R (voltage equals current times resistance)

or R = V / I leads to R = 10.4 / 0.010 = 1040 ohms (1k resistor would do)..

Again, you need to know the current and voltage drop of the particular LED in question.

Different colours will have very different voltage drops and current ratings, Blue LEDS can have a voltage drop of as much as 4.5volts and current can vary from 10 to 25ma.

Great, thanks for that. Been a long time since i had to use VIR

righto
3.3v led draws 20mA

V=12v - R=3.3 = 8.7

so now it ends up being
8.7/.020 - R=435ohms

A resistor calculator makes using multiple LED's easy.

http://metku.net/index.html?sect=view&n ... /index_eng