LED experiments
A page devoted to the tentative first steps in replacing the tiny peanut incandescant dashlight bulbs with LEDs.

Note: the pictures and text are property of the author(s). Please attribute sources if you use them.

back to mods hacks and kludges

resources:

http://www.bullisurfers.de/
(see "tipps (sic) & tricks")

http://datasheets.led.net/

http://ledmuseum.home.att.net/

Inspiration

I was inspired by the German site and by Roger's work (see below) and I tried my hand a making a LED dash light.

materials:

red LED from bike light. Unsoldered from little board, which of course meant it only had very short "legs". Checked out to be approx. 1.8 V and a narrow beam spread (20 degrees?). "Flattened" area at base of LED indicates the negative post. resistor - 470 - 500 ohm (calculation/estimation based on a dash voltage of10V and a LED voltage of 1.8)
dash light bulb holder
some 22 gauge telfon insulated tinned copper wire (scraps at hand)
heat shrink tubing

Method (made up as I went along):

drilled 1/16" hole in base of bulb holder.
Soldered 1" lengths of wire to the legs of the LED.
shrunk small lengths of heat shrink over the solder joints.
Cut one of the lengths of wire back to aprox 1/4" and removed insulation.
Tinned/soldered the exposed wire to make solid. Bent that back upon itself to make a tight "V". The other wire is fed down through the bulb holder and out the drilled hole,
The LED is pressed into the holder with the bent wire making contact with one of the internal bulb holder contact.
The LED is a good fit and the bulb holder itself "stretches" a little to hold it in tight.
I marked with a felt pen the side of the bulb holder that the LED was making contact with the internal contacts.
The wire sticking out of the base was trimmed a little and leg (trimmed also) of the resistor soldered to it.
A very short length of wire was soldered to the other leg of the resistor.
The free end of the short length of wire was soldered to the "topside" ie the side that does not come in contact with the circuit foil. This is a tricky part, you'll see how to solder it when/if you do it!
A bit of heat shrink over the resistor and wires and its done!
One has a 50% percent chance of getting it right when you twist it into the circuit foil, I don't know if these LEDs "pop" if full voltage is applied "backwards" so I inserted into foil with dash light rheostat turned way down.

Well it works, but as Roger found too, the beam is quite narrow and only illuminates the top half of the gauge. The little reflector assembly might be modified (foil inside?) but better to have a wider beam spread LED.
Inserted into the centre position, that is the bulb that lights up the idiot lights, the LED illuminates all of the icons but not evenly.

The LED does dim with the rheostat, but does not go out at the lowest/dimmest setting. But I think it was a worthwhile exercise, now I'll go get a range of LEDs and experiment further.

what an ugly little picture!

Roger's work (Dec, 2002)

"I had a little time today to fool around with the blue LEDs today and this is where it ended.

I used Radio Shack Blue LED (# 276-316 3.7 volt, 20 mA, 2600mcd, 30 degree viewing angle) with 150 ohm, 1/2 watt resistors (run cooler than the 1/4 watt ones). This gives me 4.35 volts across the LED which is just a bit under the 4.5 volt max stated on the package.

After mounting the resistors much lower along the side of the bulb base and flattening the tips of the LEDs by hand sanding them on a sheet of 100 grit sandpaper, I took this picture. I think that it is still a bit dimmer than I would like but, the tip alteration seems to have helped the "spot" lighting a bit and seems to through a bit more light onto the bottom of the gauge faces.

The attached picture is about as close to actual as I could get it and is not too far off.

By the way, reversing polarity on these LEDs won't hurt them at this voltage. At the moment, I'm happy enough to stop fooling with new combinations for a while and plan to make up a few more of these to send out to a couple of people to try out in their Vans. Let me know if you would like a couple and where you are with your testing and maybe we can get something written up for the web site.

Just to add two more cents worth... I am happy with the LED that I've been
running for a few months in the center (idiot light) position. For this one
I used an orange, wide angle, LED from Radio Shack. I liked this best as it
illuminated the idiot light symbols evenly and here, it doesn't take a lot of
light to illuminate well (as opposed to the speedo and tachometer faces which
require more because the light is reflected back onto the faces).

So far, I have been unable to find what I would like: a wide angle, super
bright, blue LED, or perhaps a diffuse, super bright would do as well. I'll
keep looking."

Mike's work (Jan 2003)

"Ok, Here,s some pics of where I ended up last week.

I bought a few 2400mcd (30degree) and a few blue 5500mcd (15degree) LEDs from superbrightleds.com. I was unsure of what I was going to use for the rest of the dash at this point so this is all I purchased. I chose to go with red for the rest of the lights because I thought that,s what the newer VWs were using.

Because I was unable to quickly source "defused LEDs, I played around with grinding them down.

The 1st change I made was choosing to relocate the LED farther out of the bulb socket (at a 90 degree angle) assuming that maybe more light would make it onto the face of the gauge. 2nd was to grind about a 45 degree angle into the bulb to defuse the light pattern. This makes the install a little trickier because the bulb socket can,t be turned around without the LED pointed in the wrong direction. If you heatshrink the leads, you can always repoint the LED. Doing this to the 5500mcd LED gave me a nice even light across the entire gauge face.

The pic shows the center dash LEDs in blue. That was a 2400 blue I was playing with. I used a Radio Shack 3000mcd ground down and sticking out of the socket. This allows you to position the led to shine to best cover the gauges.

I also added red LEDs to the heater control bulb sockets.

My current problem is finding a really bright defused blue LED for my aftermarket auto meter gauges that I added to the dash. These are side lit. I found that a ground 45degree blue 2400mcd pointed towards the top of the gauge will throw enough light around the sides to evenly lite the gauge but not with enough intensity. The temp fix was to install the red bulb "booties that came with the gauges. Now they match but I really would like them to be in blue and not red.

I have some more pics if you need them but these were the most informative. Feel free to use either the pics or the write-up where needed! Thanks again for turning me on to this!

Next project: Do you know where I can get a red lit aftermarket replacement cig lighter? I want to remove the VW unit, as nothing fits securely in the OEM hole. I bought one at a flaps in VA (for about 10$) but can,t find them in GA anywhere. Take care!"

"I also added red LEDs to the heater control bulb sockets."



in place. looks a little brighter than Roger's set-up

"Tigger en garde"