Replacing the dash light bulbs for LEDs

When I switched on my lights I could barely see my dash board lights. Changing the light bulbs for new ones, was not solving the problem. So i opted for LED's. The only problem with that is the fact you can't dim the LED's very well with the dash board dimmer. But I can live with that. That's only possible with PWM (Puls Width Modulation), you have to buy a module or build one your self.
I use two LED's for every light bulb. The resistor value, which is in series with the LEDs depends on what sort of light it is. There are two types of lights in the dash. That is the dash lighting it self, which is working between ~ 5 ~ 8 volt. And the control lighting; highbeam, oil pressure and the turn signal lights. Which are working on the normal 12 volts.
The light for the HIGHBEAM was not visible. The lens of this control lamp is to dark. I had to add 2 more LEDs, so I use 4 LEDs for the HIGHBEAM control light.

Some words about how the LEDs are installed

I used unetched double sided printed circuit board. Very thin, approx. 1/2 milimeter (0.0196 inch). I made small rectangulars, long enough to fit over the lightbulb holes. Wide enough to fit in the LEDs with ease. After I cut enough of those rectangles, I took a small strip of copper away in the middle of the rectangle. I did this on both sides. This is to prevent a short circuit. I drilled four holes in the strips, so I could install two LEDs in every strip. After this time-consuming work I soldered the resistors to one leg of the LED and cut them in lenght. Two resistors in series for the 12 volt LEDs and one for the variable voltage LEDs (that's because I had only one resistor value). After this I soldered the LED's into the strips and soldered the strips into the lightbulb holes.
I use 270 Ohm 1/8 Watt resistors. One for the 5-8 Volt. And two in series (2x270=540 Ohm) for the 12volt versions. Keep in mind that the forward current is approx. 20mA. And the forward voltage is approx. 3 volts, the same as a blue LED. The white LED's are infact blue LED's with a light filter to filter out the blue. Now you know why the white LED's have always a touch of blue in the light. And why you experience this as cold light.

How it is made

Mouseover for larger pics.
Excuse me for the bad quality of the pictures, those where shot with my phone...

Here you see the leds soldered into the light bulb holes. The leds for the dash lighting are shorter than the control leds. Otherwise they hit the instrument cluster. Originally there where blue plastic domes to filter the white light. But I removed these, to get more light. The control lights didn't have these blue plastic domes. They have already a filter, which is a colored piece of plastic with the name of the control light. e.g. OIL, HIGHBEAM etc.

Here you see the whole cluster. At the top left and right from the middle are the control lamps (oil, highbeam & turnsignal) All the other leds and the hole at the right are for the dash lighting.

Zoomed in on the left side. The circle of eight little pins are for the dashboard connector. Which connect the instrument cluster to the rest of the car.
The soldering looks like it's done by a plumber. That is because the printed circuit board has only copper on the top and bottom not to the sides. This means you have to apply a fair amount of solder to bridge the gap between the upper- and lower layer of copper.

The right side. At the right is my first attempt to install the new electronic version of the 5 volt regulator. Done with a 7805 and some capacitors.

When I tested everything, my turnsignal went crazy! It clicked in a very high frequency. I solved this by putting a resistor in parallel with the turnsignal LED. After some experimenting, i found the right value for the resistor.

After my first attempt for the 5 volt voltage regulator, I was afraid that a component could hit some metal behind the dash (all metal in a car is ground). So i found a nice place to install the 5 volt regulator. I didn't have a clock, so I've installed the regulator inside the clocks empty metal shell. For extra electrical safety the little printed circuit board is wrapped in heat shrink tube. I Drilled two holes, one for the wires and one for the 7805 heatsink.

The black wire is for extra ground. It's a little overkill, 'cause the heatsink of the 7805 is already grounded directly to the metal without any isolation. (the ground pin of a 78xx series regulator is internally connected to the heatsink)