Help on LED Dash Light Install.

floored4door

Newly Enlightened
Joined
Aug 1, 2005
Messages
3
Hello, new to this forum and figured I would drop in and say hi and ask for some help. I am wanting to change the lighting in my car to a different color (red,white,purple,etc.) But I don't know where to start. I also don't want to paint them like everyone else does. I just bought a bunch of LED's off Ebay. I know not the best place to buy but hey I got 100 LED's for .99 cents. /ubbthreads/images/graemlins/wink.gif Ok so it looks like first of all I need to use a resistor. Which ones should I use? 470 ohms as stated on ledmuseum? The ones I bought off of Ebay are 3.2v - 3.6v. Will that work with that resistor? What other recomendations do you have for a n00b like myself? I want them bright, not dull. The LED's I bought from Radio Shack are not bright at all. Where do you recommend me buying some good LED's that will light up my gauges? When I see LEDs as advertised with a viewing angle of 15 - 60 degress are the reffering to the angle you will see the light? Anything else you think I should know that would be very helpful!

Thanks!

p.s. I was looking at this page to purchase LED's but am unsure of what all the numbers mean. Like LUMINOUS INTENSITY(mcd) is this how bright they will be or?...

Here is the page.

http://superbrightleds.com/leds.htm
 

Ken_McE

Flashlight Enthusiast
Joined
Jun 16, 2003
Messages
1,687
I am wanting to change the lighting in my car to a different color (red,white,purple,etc.) But I don't know where to start.

* LEDS are a good place to start. The thing I don't like about red is
* that if a trouble light comes on the dash it won't look like anything.

I also don't want to paint them like everyone else does.

* You could use theatrical lighting gels. They have good colors.

I just bought a bunch of LED's off Ebay. I know not the best place to buy but hey I got 100 LED's for .99 cents.

* It's cool.

Ok so it looks like first of all I need to use a resistor. Which ones should I use? 470 ohms as stated on ledmuseum?

* The listing for your LEDs. Did it have a table with a bunch of
* numbers, things like "forward current"? What are those numbers?

The ones I bought off of Ebay are 3.2v - 3.6v. Will that work with that resistor? What other recomendations do you have for a n00b like myself?

* Don Klipstein has a DIY LED guide here:
* http://members.misty.com/don/ledd.html


* You could hook up a string of three of them, and another string of
* four of them, and a final string of five of them, and wire them to
* your car just to see what they do. The three will be brightest, but
* should burn out pretty quick. You can also buy LEDs that come
* with the proper resistor for twelve volt usage included. They
* have them at car part stores (but not for one cent each) and
* in the automotive section of eBay.

* Accept that you will make mistakes, but with that big pile
* of cheap LEDs you can make mistakes and not worry about it.

I want them bright, not dull. The LED's I bought from Radio Shack are not bright at all.

* They seem to specialize in little ones. You could drive
* them harder, although this cuts down on life expectancy.

Where do you recommend me buying some good LED's that will light up my gauges?

* I used stuff from Quickar Electronics
* ( http://www.quickar.com/leds.php )

When I see LEDs as advertised with a viewing angle of 15 - 60 degress are the reffering to the angle you will see the light?

* Yes. Incandescent bulbs produce a sphere of light but LEDs are
* normally directional. 15 degrees would be a narrow, tight beam,
* 60 reasonably wide, 180 is probably as wide as an LED can do.

Anything else you think I should know that would be very helpful!

* there will be a fair amount of crawling around and running wires in/
* on/under your dash. It will take a couple of goes before you get it
* just the way you like. Also, once you get good at it you may find
* yourself coming back to do the glovebox, the dome light, the trunk
* light, underbody lights, in-the-wheel lights, a crstal-skull-stickshift-knob
* with UV lights in it, etc. The CPF people
* will be absolutely no help with fighting the addiction. Heck, they'll
* offer to sell you stronger pharmaceutical grade lightingf!

* Are you familiar with how to wire them together, know that each one has a positive side? I think the longer leg is the positive side.

p.s. I was looking at this page to purchase LED's but am unsure of what all the numbers mean. Like

LUMINOUS INTENSITY(mcd) is this how bright they will be ?...

* Yes. Millicandles are small. More = brighter.
 

floored4door

Newly Enlightened
Joined
Aug 1, 2005
Messages
3
Wow! Holy ton of useful info! This is what was stated in the auction:

Size: 5mm / 0.2 inches
Voltage: 3.2V - 3.6V
Reverse current (uA): <=30
Luminous Intensity Type Iv (mcd): Average in 10000 for the clear white and 5000 for color LED
Life Rating: 100,000 Hours
Viewing angle: 25 - 35 degree
Absolute Maximum Ratings (Ta=25°C)
Max Power Dissipation: 80mw
Max Continuous Forward Current: 30mA
Lead Soldering Temperature: 240°C ( <5 Second )
Operating Temperature: -25°C to 85°C
Preservative Temperature: -30°C to 100°C

As for wiring the Led's I am aware of the positive and negative sides. My question is when wiring 3,4,or 5 led's up do I use only one resistor for 3,4,or 5 or one for each LED?

When wiring them do I wire in series? Anychance of a diagram of how I should wire them? Positive to negative and so on? Thanks for the help I really appreciate it!
 

Ken_McE

Flashlight Enthusiast
Joined
Jun 16, 2003
Messages
1,687
Direct Driving LEDs in Series

Let me explain a little about using LEDs in series. In the picture below the letter "U" represents one LED lying on the table with its leads facing away from you. On the actual LED one lead will be longer than the other, to show you which is the positive and negative side. I don't have a font that will do that so I have put a '+' and a '-' sign next to it to show which is which:

Negative lead -U+ Positive lead

Now in the LEDs you bought the specs say "Voltage: 3.2V - 3.6V' This means that this LED, all by itself, will start to light at around 3.2 volts and you can safely run it up to around 3.6 volts. If you have a 3.5 volt power supply you can just hook it right up and it will run just as happy as you please.

I will mention that it will give you the most millicandles per watt and the longest life expectancy when you are underdriving it, running it lightly, powering it more towards the 3.2 volts end of its range, not the 3.6.

100,000 hours burn time is what the industry uses as an average life expectancy for an average LED. Since this is possibly as much as the life expectancy of your car, you really don't need to concern yourself with running the LEDs lightly, the car will probably die before they do.

Now lets say your car doesn't have a handy 3.5 volt power supply in it. You can take two LEDs and hook them up in series, like this:

Negative lead - U+ -U+ Positive lead
______________A___B________________
In this picture the negative lead to your battery (in a car just grounding it to the body will connect you to the negative side of the battery) goes to the negative leg on LED "A". Then you have a connection from the positive leg of "A" that goes over to the negative leg of "B". From the positive leg of "B" you connect to the positive side of your battery. Now you have two LEDs in series.

So what will they do when in series? They will attempt to split the current between them, each one taking about half of what is available. So if you take 3.2 volts for "A" and 3.2 volts for "B" this gives you 6.4 volts. You will need around 6.4 volts to get them to light. The safe max for each LED is 3.6 volts. 3.6 x 2 = 7.2, so the two running together in series should work nicely in the range from 6.4 - 7.2 volts.

Let's add another in series, like this:

Negative lead - U+ -U+ -U+ Positive lead
______________A __B __ C

The negative lead from the battery goes to the negative side of "A",
"A" has a connection from its positive leg over the negative leg of "B",
"B" connects its positive leg to the negative side of "C",
the positive leg of "C" connects to the positive side of your battery.

Each LED will try to take its fair share of the voltage. Since there are three of them they will try to take 1/3rd of it apiece. each one needs 3.2 volts to light, 3.2 x 3 = 9.6, so you will need at least 9.6 volts to get them to light. They max out at 3.6 volts each, 3.6 x 3 = 10.8, so running three in series you will need 9.6 to 10.8 volts to run them safely.

You can hook up as many LEDs in series as you want. If they are all the same kind they will try to share the current evenly.

Now about that car. Officially your car has a twelve volt system, so you would think you could just take twelve and divide it by three LEDs in series, each one would get 4 volts, now they're overdriven, but you wanted bright anyhow, OK, so you go around hooking up groups or three LEDs in series and use them around the car, you're all done right?

Sorry, you're not. There's something the maker of your car didn't mention. That 12 volts is just a goal, an average. In practice you might hit 13 or 14 volts when you step on the gas. You car doesn't care, everything in it was built to take it, but your clump of LEDs will notice. they'll take that 14 volts, divide it by 3, 14/3 = 4.6 volts, that kind of overload will blow them up like popcorn, they'll be dead before you take your foot off the pedal..

So, in the situation I describe above, where you are directly driving LEDs (direct drive means you don't have any kind of protective circuits or resistors standing between the power supply and the LED) you have to be careful because a small difference in the power supply can mean life or death for your LEDs. Since you have LEDs to spare, you can test different setups just to see for yourself how they work, what makes them run dim or bright or fail.


RESISTORS:

I'm not really going to get into current regulators or resistors here because I'm not good at them, but I'll try to address your questions about how you use resistors.

You could take one LED and hook it up to a stronger resistor, then just run them as a set separate from everything else. This works. It is a little less efficient because the resistor is using more power than the LED, but in a car you've got power to spare so you don't care. In a flashlight you would care because your power is limited. A nice thing about this setup is that you only lose one light if a component fails.

You could hook up two LEDs in series and use a medium resistor since it only has to throttle down 12 volts to 7 or so. (the two LEDs will divide that 7, get 3.5 each, they'll be happy)

You could hook up three LEDs in series and then use them with a small resistor, since it only has to get that 12 volts down to 10 volts or so.

Now, you can't just go down the Radio Shack and ask for "a big resistor". If you do, the kid at the counter is liable to get out a ruler and see if they have any two-inchers in stock. Resistors are measured in Ohms. The greater the number of Ohms, the stronger the resistor. I'll suggest Funkazoids link for figuring out what size (how many Ohms) resistor you need.

WHERE DOES THE RESISTOR GO?

Once you have your LED/s and a resistor the resistor can go pretty much anywhere in the circuit. It can be between the negative side of the battery and the LED. It can be between the positive side of the battery and the LED. If you have LEDs in series you can stick it in between the LEDs, they won't care.
 

Blackbeagle

Newly Enlightened
Joined
May 14, 2002
Messages
199
Location
Oahu, HI
Bright may not be better.

Just a comment - if you use very high brightness LED's - the inside of you car becomes very bright, particularly your dash which is facing towards you. Now, look out the windshield, it will look even darker out there. What you may end up doing is compromising your night vision. Bright might not be what you really want under those conditions.
 

stormchaser

Newly Enlightened
Joined
Feb 12, 2005
Messages
50
Re: Bright may not be better.

good point . could a variable knob/switch be used? brighter during day. dimmer at night
 

AESOP

Newly Enlightened
Joined
Mar 15, 2005
Messages
85
Location
Canada
Re: Bright may not be better.

Sure.
A variable switch is simply a variable resistor. you just need to ensure that you can't overdrive or under drive the LED's too much.

Michael
 

Darell

Flashaholic
Joined
Nov 14, 2001
Messages
18,644
Location
LOCO is more like it.
Help on LED Dash light install

Most dash lights are controlled by a variable resistor already, so over-brightness should not be a problem.

Swapping the instrument cluster lights for LEDs was one of my latest projects on the EV, actually: http://www.darelldd.com/ev/rav_dash_led.htm

Looks like there are enough good responses here to get you rolling. Do remember that the voltage when driving the car is not 12, but is closer to 13.8. Good luck!

And please note: do NOT change the subject of a thread unless there is a good reason to do so!
 
Top