car interior questions

[Vincenzo]

hi, i made this account solely to ask a few questions. Now what i'd like to do is throw a few leds in my car to light the area under the dash and chairs where a person's legs would go. i'll probably end up using anywhere from 30-60 leds. i've been researching on the net a bit and know the basics of what i have to do. what i would like to know is if there is something out there that i could buy that i could power with my car battery that has the necessary resistors and multiple terminals to connect several circuits.

i plan to connect it at the fuse box in my car and between the two put a switch.

also if i could get some opinions on how many leds i should put in one circuit that'd be great.

if i am completely wrong on how i think i should do this any advice is much appreciated
thank you
Vince,

 

[alpg88]

kinda yes.
e bay is full of prewired 5-10mm leds for 12v, also there are alreaby made led strips for cars, just go to ebay and ebay motors, type in leds, and led strips, and you'll see tonns of stuff.

 

[Vincenzo]

is that the only option really? i wanted to do it from scratch just for the sake of learning and possibly expanding later on. could i splice one line from the battery say 20 times for a whole bunch of lil series circuits?

 

[bshanahan14rulz]

Vincenzo,

with lower power LEDs, it is usually ok to make multiple series strings in parallel.

http://led.linear1.org/led.wiz

Helps. even tells you what resistors to use.

Basic idea is that you have 12V available to drop. Each LED drops a certain amount of voltage, so use up as much as you can. You will inevitably end up with some extra voltage that needs dropping but isn't enough for an LED. You will use a resistor to drop the rest of the voltage, using R=V/I, where V is how much voltage you still need to drop, and I is the current you want going through the LEDs. Or you could use the LED wizard which does all the maths for you :thumbsup:



I'd suggest regulating the voltage to 12V, making sure the regulator can handle the total current draw of the entire array and resistors. I used a Sharp PQ12RD21 regulator in my setup, so that I could also use a PWM generator to dim the lights. PWM was overkill, but it was fun for me, so I did it. PQ12RD21 I don't think is in production anymore, but some people more familiar with electronics might be able to point you in a better direction for finding a suitable 12V regulator.

 

[alpg88]

http://wolfstone.halloweenhost.com/Lighting/litlpo_PoweringLEDs.html

 

[Vincenzo]

wow thanks so much guys. that was a lot of help and is much appreciated. I am going to start ordering everything i need on monday is ebay my best bet for prices? i didnt really want to order off superbrightleds but what would your recommendations be?

 

[jason 77]

wow thanks so much guys. that was a lot of help and is much appreciated. I am going to start ordering everything i need on monday is ebay my best bet for prices? i didnt really want to order off superbrightleds but what would your recommendations be?

If you are talking about using 5mm LEDs for your project then you could go and buy them on Ebay for cheap, and they would probably work fine. I would just under drive them and make sure you use a good voltage regulator.

As far as the other electronics I would go to a quality site like say Jameco, mouser, or futureelectronics. Depending on where you are Jameco is quick, I get my orders practically the next day as there is a wharehouse near me.

 

[JohnR66]

Cheap Chinese/Ebay LEDs are JUNK! Get quality LEDs and you don't need as many because you don't have to underdrive them to make them last plus they are brighter.

If this is for a night accent light effect, you may want to rethink the number of LEDs. 30 to 60 of the little boogers is going to be bright enough to ruin your night vision.

With automotive voltages, three white (or blue) LEDs in series with 150 Ohm resistor is a good starting point. With the engine on, this gives you around 4 volts to drop in the resister and current is 26.6ma.

I'm a fan of the Radio Shack 276-0017 neutral white LED. Three in each foot well will light nicely. The dash depends on exactly what you want to do. I can't see a lot of light needed there.

Do NOT operate this stuff while driving at night and be sure you can't see the LED directly due to the dazzling effect of the intense point source of light.

 

[blasterman]

You guys can't be serious about running LEDs direct off of automotive DC, right? Not only can you not find two cars that match, but the voltage tends to bounce all over the place. We shouldn't be discussing resistors here - at all.

As per above, you need a regulator to do this, which is nothing more than a beefy 'buck' type supply. Or, stick with autmotive type accent strips with the regulator built on and designed to be plugged directly into car DC. I realize that some of this stuff is often just resistor driven, but it beats the guess work and is basically plug in play. SuperBrightLEDs.com has pages full of this stuff.

 

[bshanahan14rulz]

A 150 Ohm resistor is big enough to keep problems to a minimum and will work longer than 4 LEDs with a smaller resistor. Voltage regulator is still the way to go, unless you're wanting to use high-power LEDs, which are more complicated.

Also, most "plug-n-play" LED strips and kits are regulated with only resistors. You have to look really close to make sure they're only fitting 3 per series and not trying to run 4 in series, or to make sure that they actually have a voltage regulation circuit built-in.

 

[JohnR66]

I'd agree to use a regulated driver if budget allows. However, foot well lights are hardly mission critical lighting. The incandescent lamps aren't regulated anyway and their output is also pretty sensitive to supply voltage.