Using 3mm LED's in vehicle, need help.

[-Spazmatic-]

Hello all. I will be putting in some LED's in a sort of a "fake" showcar (kind of an inside joke) but I have a lot of questions because I know nothing about resistors and LEDs and whatnot. Basically, I'm putting 2 LED's in each of the air conditioning vents in the car. There are 4 vents...so there's 8 LEDs. I'm then going to put 5 LED's under each side of the dash, making it around 18-20 LEDs (may put 6 under each side). How would I go about wiring that up? I would like to do it in a series and have them hooked up to a rocker switch, is this possible? Here's the description of the LEDs :

Description

Emitted Colour : Red

Size (mm) : 3mm

Lens Colour : Water Clear

Peak Wave Length (nm) : 620 ~ 630

Forward Voltage (V) : 1.8 ~ 2.2

Reverse Current (uA) : <= 30

Luminous Intensity Typ Iv (mcd) : 4000(Typical) ~ 5000(Max)

Life Rating : 100,000 Hours

Viewing Angle : 20 Degree

Absolute Maximum Ratings ( Ta = 25°C )

Max Power Dissipation : 80 mw

Max Continuous Forward Current : 30 mA

Max Peak Forward Current : 75 mA

Reverse Voltage : 5 ~ 6 V

Lead Soldering Temperature : 240°C ( < 5 Sec )

Operating Temperature Range : -25°C ~ +85°C

Preservative Temperature Range : -30°C ~ +100°C

Quantity : 100

Free Resistors (Work for 12v)


So....................................can someone give me a hand? 

EDIT:

Oh, and will these LED's be bright? I want them to glow at night (not direct light, I'm going to point them backwards so they'll just give off a nice glow)

[Rob]

Welcome to the boards.

Since they throw in the resistors, the way to go would probably be just add one resistor to each LED. Then every one would need to be connected back to your fuse block or cigar lighter or wherever you grab power from.

Your battery can power multiple LEDs in series, but then you'd have to go and buy resistors. I'd use the freebies, one per LED.

[-Spazmatic-]

Alright I will do that. I have another question though.


I am going to be wiring these LEDs to a single switch that will then go to the fuseblock or cig lighter or battery. Will it work this way? How would I wire it? I have decided I would like to have 3-4 LED's per vent and none under the dash (like I was thinking). This will be 12-16 LEDs.

[justDIY]

wire it so you only end up with one postive wire in the end ... in other words, wire all the postives together and all the negatives together ... connect the negatives to body ground whenever convinent, then you only need to worry about routing a single postive wire, branch off as needed, and put your switch on that wire.... be sure to throw a 1a fuse on there or whatever you've got laying around.

[-Spazmatic-]

Cool, those were my original plans.


Final thing, should the resistors be on the positive side of the LEDs or the negative side? Also, the switch has 3 prongs (ground, active, and power), would I not use the ground prong if I just bolted it to, say, a body bolt?

[justDIY]

is it a lighted switch?  that is the only reason I could think of that a DC switch would have a ground connection.

or is it a double-throw switch ... you have something like on / off / on or on / on, with a common terminal and two switch terminals.

regarding resistors, you want to attach them to the anode (the postive lead)... I'm pretty sure it's anode, but I'll have to look at an led to make sure.   It makes no difference electrically, but your resistors are going to get pretty warm dropping at least 9 volts, so connecting the resistor to the bond-wire side (anode) prevents heat from affecting the LED.

[-Spazmatic-]

Alright thanks. Yes it's a lighted switch, I just realized that. That means that I will have to ground the switch itself, and also ground the LEDs to a ground in the vehicle, correct?