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All About “LED Tuning” your car

The Challenge
First of: Know what you are getting yourself into... To do something like this you have to be a little crazy! Or a freak!
Also good to know: You have to open your dashboard, remove your instrument cluster and open it, because you need access to the of the instruments. Its a lot of work and a nice challenge!
On top of this you could also change the bulbs in the knobs and buttons to LEDs, in the dashboard as well as in the doors. You could Add LED Lighting to the storage places in the dash and the center console, add LED lighting to the climate control unit, have a a nice deep blue glow spread out over the floor and pedals and add lighting to the door handles. That last one makes the handles findable in the dark, but also makes the cockpit area look wider in the dark.
If you give it a lot of time and attention the result is usually astounding and you should have an enormous fulfillment thanks to the work you have done. You now belong to a select group of people that always get the attention at car meetings because of their interior lighting!

What’s it going to cost?
One of the important issues of course is: “What is it going to cost?”
It’s a good idea to first make a picture of your instrument panel.

First make a picture of your instrument panel.
In a cad or drawing program you can indicate where you want the LEDs on the instruments, and in what color. For this you can use any graphical drawing program such as Paint in Windows (can be found in the start menu under accessories) where you can use the brush tool (the spray can icon).

Brush over each number, symbol and text with a colored dot.
Each number on you panel will need a LED, but also symbols and other texts will need to be illuminated. This way you can count out how many LED you will need of each color. Even though you cannot see the numbers any more, since you have painted over them with the dots, you will be able to get a pretty good idea of how its all going to look when you are finished.
Switches also can be equipped with LEDs, however you will have figure out how a switch works and remember how to connect it again. Which connectors are for the switch itself and which connectors are for the light. For the LED it’s important to know where the “+” and “–” of the switch are and if there is room for the required extra resistors.

Add up the number of LEDs per color and check the prices. In the example above we have 65 blue LEDs, 9 red LEDs, 1 yellow LED and 2 green LEDs (indicators). In the example we have also added LEDs for the lights of the symbols and warnings (oil pressure, temperature, doors, ignition, indicators, etc.). The other parts of the car that could have LEDs added to them, like mentioned at the top of this page, have not been taken into account in our calculations:

Cost calculation:
Color of LED	Number	Price for each		Total Price

Blue	65	€	1,00	€	65,00
Red	9	€	0,25	€	2,25
Yellow	1	€	0,15	€	0,15
Turqoise	2	€	1,70	€	3,40

Total				€	70,80

These prices are only an indication based on the prices around may 2005. In the calculations we have also not taken into account the extra resistors that will be needed for the job. However, because resistors are relatively cheap and you could reduce the amount needed by connecting LEDs in series, these costs compared to the LEDs themselves are minimal.

How long will it take?
It is a lot of work and you need to take your time... Once, on another website, I saw a instrument panel where the LEDs were all over the place and they tried to illuminate a quarter of the panel with just one LED! A extensive and tidy approach will give the best results, take your time and do it properly, because once you have put it all together again you will be looking at the result every time you go for a drive... for years!

From personal experience with the neat and tidy method we can tell you it takes a bout a day to do a instrument panel. You do not need to open that many items, but there is usually 3 or 4 gauges that have a lot of LEDs. So all in all still a lot of work... Also during the build you are regularly hooking it up to a power source to check how it looks and if all the LEDs are connected the right way round. If not then the LED will not go on and all other LEDs that are in series with it will also not illuminate.

If along with the instrument panel you want to LEDtune to your center console, switches and climate control as well, then even though there are going to be a lot less LEDs, you are going to have a lot more work with all the separate parts such as opening the switch checking the polarity and sometimes also removing some of the plastic housing of the switch to make room for the LEDs. All this will easily add a day to your project!

Use this extra time, you will need it! Also you will enjoy the result for years so if you mess up somewhere you’ll have to look at it for a long time... However hard you try sometimes some of the results will be good, but not perfect. Accept this, because if everything has been done perfectly a small slip will not be noticed anyway!

Now get to work!
You are going to need some tools:

A solder Iron
Solder tin, with a reson core 60/40 (tin/lead ratio) *)
A small pair of cutting pliers
A flat pair of pliers (for bending)
A vile or a grinding stone (for adjusting LEDs to larger spread angle)
Some flexible wiring
Some rigid bare wire 1mm diameter
Small pieces of holed circuit board 7mm by 7mm

As of 2006 it has been determined by law that no hazardous materials are allowed to end up in the environment. Also when developing new products no dangerous materials may be used. All materials have to comply with the “RoHS” (Restriction of Hazardous Substances) guideline.
One of these materials is the heavy metal Lead, that is still used in today’s solder tin. Companies that work with this need to switch to alternatives. For use in hobbies this will not be as important for the time being. All electronics and electrical systems in cars, but actually in all electronic devices that date from before 2006 make use of tin/lead solder connections.

The small pieces of holed circuit board can be glued to the back of the instruments dials. On the copper pads you can solder two rigid copper wires in the shape of a large arch. These wires should be “floating” above the the instrument plates. Of course before you do this you need to be sure tht there is enough room in the instrument panel once it is closed again!
Along the wires add some support struts of equal height. You need these two wires to power the LEDs one is “+” and one is “–”. These wires are not allowed to be connected to each other electrically, so for the support struts use different islands created from small pieces of holed circuit board.
Onto these two now stable wires the LEDs are going to be attached together with their resistors. As can be seen below.

Pay attention to the small piece of circuit board, the two wires and the LEDs that are connected per 2 in series.
Can we widen the small light spread of the LEDs?
Because the LEDs have a reasonably small spread angle (30 or 60 degrees is a normal spread) you will not get evenly dispersed light. Due to the fact that the LEDs are built in and very close to the dial plates they should have a very wide spread angle. So that they light up the numbers evenly. There is a little trick to accomplish this. Depending on the gradient of the spread you can do the following:

You can sand the head of the LED with some rough sanding paper (roughness 60). The light spot will get much softer edges, but the spread will not change much.
You can fatten the head of the LED with a vile or a grinding stone. The spot will fade and the spread increases significantly to somewhere between 90 and 120 degrees.
You can turn the head of the LED into a point. The spread of the Led will now be almost 180 degrees! The light will also be spread out to the sides now.

Be mindful and use a dust mask or dust ventilation, because this process procduces miniscule dust particles. Al lot of people also saw through the epoxy printed circuit boards, which produces the same type of dust particles. The effect of breathing in these tiny dust particles is unknown but it is always better to avoid it if possible!

Dust masks can be bought at any DYI shop for relatively little money. So use one when your working on adjusting LEDs or sawing PCBs!

Mechanically speaking you can really remove a lot of plastic from the LEDs but you can go too far. If you happen to remove the thin wire that runs to the middle of the chip, well... get yourself a new LED and be more careful this time.
Additionally Even with the sharpened LEDs you might still need an even better spread of the light for LEDs behind a LCD screen for example, where you the background to be lit up. To accomplish this you could use a diffuser (a milk-like semitransparent plastic filter) halfway between the front of the LED and the back of the LCD screen.

How to Connect?
For connecting the LEDs I would like to redirect you to our other page LED technical, where a lot is explained about threshold voltages and about connecting LEDs in series.

Globally one can say you can only connect two blue, blue/green (turquoise) or white LEDs in series together with a single resistor of 470 Ohm and ¼ Watts. The current will then be about 15 mA using a supply voltage of 14.4V, which is about the voltage of your on-board Circuits when driving.
Four red or yellow LEDs could be connected in series with a resistor of 470 Ohms and¼ Watts because the Threshold Voltage of these is almost half as high.
With this in mind it might be handy to use an even number of LEDs, because if you only connect one LED with a 470 Ohm resistor that LED will be brighter then the others. You could have a higher resistor but that will give you issues is the dashboard has a dimmer!

If the Dashboard does have a dimmer, which is usually the case nowadays, then it controls the Voltage on the lighting. Because all the lights were connected in parallel and were of equal power, the entire dash dims with an even light distribution. With LEDs this is different. This because the have a threshold voltage that is different per LED color. So for LEDs its important to make groups of LEDs that are connected in series, these groups need to have a combined threshold voltage that is approximately equal. If you don’t do this, and have a single blue LED connected with it’s own resistor with a corrected value of 750 Ohms, then at full power (14.4 V) the LED will be just as bright as all the other ones. Now when you drop the dimmer to about 7 Volts, then all LEDs are almost off because two LEDs in series is approximately 7 Volts. However the LED that was connected alone that alone has a threshold voltage of 3.5 Volts, also has 3.5 Volts over his resistor of 750 Ohm (the other resistors are almost 0 at this point) and there will still be a current of about 5mA! So this single LED has only dimmer to about 1/3 of its original brightness.
Because of this I usually use a “dummy” LED. Whenever I end up with an uneven number of LEDs, the blue one for example, I add an extra dummy LED, blue in this case, and point it in a completely different direction, backwards for example. It will only cost you one Euro but it will fix your dimmer problems!

Life Expectancy
LEDs are specified with an enormous life expectancy, approximately 100.000 hours of longer. This will be true for most production line LEDs used under normal temperatures and conditions. But not all LEDs are of the same quality when they are produced, there is some spread in the quality, wavelength, brightness and life expectancy. Especially that last one can not be seen from the outside. We all know that light bulbs made by Hollands most famous producer can die on us long before the specified 1000 hours, sometimes even after only a few days!
LEDs last longer, but on board of a car in a dash that in the summer can reach temperatures as high as 80 degrees and in the winter can drop to -15 degrees just as easily, and where we also have things like voltage spikes on the electrical network of the car, the LEDs are going to have a pretty hard time. The biggest of the problems is the high temperature that the dash reaches in the summers. If you turn on the LEDs with a reasonably high current (25mA for example because the maximum is specified at 30mA) then the LED will get far too hot. This is due to the addition of the heat resistors (Rth JL (Junction to Lead Frame) + Rth LA (Lead Frame to Ambient)) and from the LED to the environment there is hardly any cooling going on, inside the instrument panel...

LED contruction

Because the expansion coefficient of the LED housing is different tot hat of the LED chip, mechanical stresses will form around the bond-wire ( thin wire that runs to the center of the chip) and the wire can break. This leads to flashing of the LED and eventually to a complete breakdown of the LED. Due to the fact that the current can no longer pass through the bond-wire all the other LEDs that are in series that used to flash together with the broken one also will no longer work. This can happen after only a few months, after a few year it could l be possible that 10% or more of the LEDs have broken!
Because you usually do not want to drag out the entire dashboard just to replace a few broken LEDs I usually stick to 15mA for the LEDs, this because I have had some good experiences with 15mA. It is true that at higher currents the amount of light will in crease but due to the resulting high chip temperature that will not increase in the same ratio as the current. The light emittance actually is not that much more but the life expectancy will be a lot shorter!

It is a special case when the LEDs are mounted in the headlight units of a car as parking light, usually done with a foothold called W5W (because of the wedge edge, glass/plastic socket) or BA9S (bayonet, metal can socket). These LEDs are usually close to the halogen bulbs in an area that get pretty hot and that has little to no ventilation! Almost all of these LEDs will break within the first few months.
In my T-Bird the LEDs are placed in the rear housing of the headlights (with the reflector layer), in which I have drilled holes and glued the LEDs so that they only just stick through into the headlights. These LEDs are also set to 15mA per LED. Thanks to the airflow behind te headlights while driving the LEDs will be able to operated at a slightly lower temperature. After two years mine are still working. And if you cram it full of LEDs you will have a lot of light even with the lower current!

Other influences that occur in a car are high Voltage spikes on the 12V circuit, which is usually caused by switching inductive loads such as the starter engine, electrical windows, electrical sunroof or electrically unlocking the boot. These Voltage spikes can reach to over the 100 Volts! Also under the bonnet there are some inductive loads like the dynamo itself could add a ripple of spikes on the circuit (the speakers might “whistle” if this is the case).
In a car the LEDs will be in a damp environment. This would appear to be fine because the housing of a LED looks like it is waterproof. But the plastic (epoxy) is actually hygroscopic for water, meaning it will let water pass through it, just very slowly. Over time the LED chip is sensitive to this water. Because of this there are special purpose LEDs that are made for these extreme environments, that have a different housing that is not hygroscopic for water. Aligent produces these types of LEDs for example, but they do come at a price. In some branches of industry that higher price does not weigh up to the added reliability of the LED, and simply replacing the LEDs would be an cheaper solution.
Tot slot is het van belang om de LED’s met voorzichtigheid te behandelen, de zijn gevoelig voor elektrostatisch elektriciteit (ESD), juist vóórdat ze aangesloten zijn! And finally it is important to threat the LEDs with care. They are sensitive to Electrostatic Discharges (ESD), especially before they have been connected! The Electrostatic Discharge of a sweater could be enough to deal a “invisible” blow to the LEDs. This does not make the LED any happier, and it will let you know by being the first to stop working!
Needless to say the solder iron should be set at 330 to 350 degrees Celsius, and a longterm heating of the LEDs connection wires should be prevented.
In conclusion even under ideal circumstances the LED’s light will diminish over time. The “end of life” is usually defined when the amount of emitted light has halved. Green, blue, violet and white LEDs usually also show a shift in color (for white LEDs color temperature) during this time.

About the colors of the LEDs, what can and can’t you do?
Instrument panels in cars are usually lit by light bulbs. The bulbs have a warm white color, the color spectrum is stronger on the side of the longer wavelengths (700nm) what we see as red, and the color spectrum is weaker on the side of the shorter wavelengths (400nm) what we see as violet light. Because a bulb has a glowing wire, this will get very hot and will start radiating heat, light with higher wavelengths; infra red light (IR). In “white” light usually the color temperature is used in in stead of the wavelength. Warm light such as a candle has a low color temperature (1500K (where the K means Kelvin)), and cool white-blueish light of a HID car headlight (Xenon) has a high color temperature (8000K).

CIE curve with color wavelengths and color temperature.
To make the light in the dashboard appear orange, amber or green while still using white bulbs, colored semitransparent plastic plates are used, a sort of colored filter. Due to the low color temperature of the bulbs a orange or amber filter (as used in a lot of BMWs) will not cause a lot of light loss. Not a weird choice it would seem.
But cars that have a nice green filter still display as a strange dull green color, that is caused by the same bulbs with their low color temperature and where green is a much weaker spectral component of the bulbs light. So a green filter will stop more of the light from passing through it.
Creating a blue effect with bulbs is quite a challenge... Sometimes we see garden lighting that is blue or Christmas lighting with a blue paint. But the light is usually a lot weaker then that of their orange or red counter parts. And the light is not really even a nice deep blue. In Christmas lighting you see white glowing wire in the bulbs, which we cannot use at all in our dashboard handy work.

It should be clear that the nice pure colors of the already very bright LEDs would be a nice solution for these problems.
But shamefully there are still limits to what we can do with LEDs behind greens and orange filters. It is impossible to get a blue LED to shine through a orange filter for example. U could get red light to shine through it, but not blue. The same goes for a green dashboard, U cannot shine through this green filter with a red LED.
In LEDs the color is specified by wavelengths. Which is the wavelength at which the LED gives its maximum power (peak wave length), in other words the color that is most dominant. But because a LED never only has only one single wavelength, but also emits some wavelengths just around the peak wavelength (sidebands of the less dominant colors) there will also be colors emitted with slightly longer and shorter wavelengths.

Color wavelenght

This all means that a red LED of 635 nm also emits less powerful colors with a longer and shorter wavelength; deep red with a wavelength of 660 nm and orange with a wavelength of 600 nm. Due to the color rendering of our eyes (visualperception) all these colors are mixed into the average color that is most dominantly present for us. The average of the colors in the upper and lower sidebands are that of the central dominant color.
So what if we shine this red LED light through an orange filter? This will cause a sort of visual filtering to occur on the small band of red light the light has become less deep red for our eyes because the longer wavelengths (deep red) are blocked more then the shorter wavelengths ( orange).
The same goes for green and blue filters. The color will turn blue, even though this blue is not pure blue edges towards the green side. A friend of mine had a nice name for this; “messed-up blue”. But still the result is a lot better then the old fashioned light bulbs!

Blue LEDs behind a green filter.

The effect of blue LEDs behind a green filter.
If the filter had more of a blue-violet color, then the shortwave spectral components (deep blue) are passed easily, and the longwave spectral components (blue-green) are diminished. Because of the color rendering of our eyes the nice deep blue tint with a hint of violet will appear.

Blue LEDs behind a blue/violet filter.

The effect of blue LEDs behind a blue/violet filter.
I hope this example has been able to make the effect of filters clear.

In some cars (like old BMWs) the instruments are lighted from the front. The advantage of this is that U can use white back planes in the speedometers and shine onto them with a blue light. This way they will be able to reflect a very nice deep blue light (even if you do see the shadow of the needles on the back plane). You could scan your backplanes into your PC via a scanner and edit them images with graphics or art for the backgrounds. You can see what that might look like on the page LEDs in BMW 324.

Have fun tuning your car!