Russ's 2.1 SED Auto now in Mandarin

[djg]

Ciaran, to the thoughts about dash bulb replacement: among the many on the market, physically fitting into the sockets but providing poor light output, very concentrated as you mentioned, there are a few extra ones with a high intensity LED on top and four or five other LEDs on the rim, providing side illumination in 360 degrees. More expensive, though...

Not the web site, I don't know them, just for an idea: http://superbrightleds.com/moreinfo/min ... -base/199/

It might be rewarding to experiment because some bulbs (warning light bulb directly below the lit area) might not need it while other places (general backlighting, LHD display, clock) really do.

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[russ92xmsed]

Russ, I started to contemplate another, only slightly more involved solution to the switch illumination problem. A small circuit board that fits into the cavity of the blue gadget, with the SMD LED and resistor mounted directly. This would have the advantage of emitting light right in the centre and upwards. Besides, the resistor wouldn't protrude to the side.

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Thats interesting. I would like to see what you can do. I was following a method already tried by the Dutch XM club. But the instructions were incomplete, so had to work out some of the problems.

[djg]

Time permitting, I'll collect a handful of LEDs and resistors, all the rest is at hand. And I already have a plan of how to do it exactly...

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[djg]

It would be as simple as on the attached picture.

Capture.png

You need a 470 ohm resistor (the 1206 SMD size would be already enough but 1210 would do just as well) and the LED. The second could also be either 1206 or 1210 in size. Choose a green LED with 90-120 degrees of view angle.

Solder the resistor and the LED together (if you want to be consistent in the orientation of the green gadget, settle on either the cathode or the anode of the LED and use the same in all switches). Solder thin wires to each end of the resistor-LED combo, long enough for them to reach outside, to the sides. Either use separate thin wires or dismantle a larger cable and use the individual strands cut to length.

Put the resistor-LED combo into the green gadget, LED facing downwards (to the inside), approximately in the middle. If you want added safety and ease of installation, cut a thin, long strip of plastic from any blister packaging material you have lying around. Push the strip between the resistor-LED combo and the wire on the side (colored red in the picture). Place the two output wires neatly in the original places, protruding to the outside world. Use a hotmelt gun to put a blob of glue to the bottom of the green gadget insides (colored yellow). This will probably glue the plastic separator as well, so just cut its protruding part with an exacto knife. Route the wires to the sides, wrap them around the pegs, re-assemble (as Russ described earlier, either you have to think about the polarity in the circuit or test after half assembly, green gadget in place, base of the switch temporarily connected; if it doesn't light up, turn the green gadget the other way round).

[russ92xmsed]

This sounds very interesting. Are you going to do it, love to see the results.
One thing I did find, don't use a green LED. They aren't strong enough, .... Well the ones I used aren't. The Green comes from the switch, so a good bright white bulb will do it.

[djg]

Yep, I'll go out for the components on Monday. I'll also make pictures, of course.

As to the color, I'm really not sure. At first, I also thought about white. However, whatever brightness they specify only applies to white then. When the internal parts filter it to green, much of it will be wasted. On many LED websites I saw recommendations of selecting the proper color in the first place, so that this loss can be minimized. That's why I planned to get green but with the appropriate brightness (or, at least, hopefully).

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[xmexclusive]

To use LED's successfully you need constant voltage and current limiting.
In normal circuitry the voltage range can be designed to be minimal.
In that situation a simple resistor can be calculated and used to operate a LED at the chosen light level.
With this chain circuit quite small voltage reduction will put the LED out while significant over voltage will burn out the LED.
This is why LED dimming is so difficult with this type of circuit.
Light output matching with multiple LED's is another problem area as the individual devices as produced vary.

For the last week I have been monitoring the voltage in the XM that I have been using.
It varies from around 9 volts to just under 14 volts and fluctuates quite a lot.

As a result for my LED project (10 watt 3x3 matrix devices) I am using constant current, constant voltage modules.

The quality replacement LED bulbs now on the market contain similar circuitry.
It has taken the Chinese a little while to refine the design of Car LED lights to get reliable results.

John

[djg]

You won't get a voltage as high as to harm this LED. And if you do, the LED will be the least of your worries...

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[White Exec]

It's not voltage per se that will blow an LED, but the current that flows through one. Component LEDs themselves (as opposed to "packaged" LEDs for 5v, 12v or... operation) have almost zero forward resistance, and the external resistor for each one (or small groups of them) must be chosen to limit that current to the specified/required figure. You can run an LED from 100v if you wish, but just choose a suitable resistor!

John is right to go down the voltage regulator route. For a fixed network of LEDs, resistive dimming (with regulated voltage) is possible, although purists prefer a pulse width modulator approach.

For me, this isn't a good time to be playing around with dash illumination, because the breakthrough into 360deg LEDs hasn't really happened yet, and the best that seems to be available are some rather clumsy multi-LED units, made up with discrete LEDs. I know it's a fascinating challenge, but given the exceeding long life of OE miniature tungsten lamps - aided enormously by NOT operating dash illumination at full-on - is it really worth the effort with the existing devices? The biggest hurdle for many owners is the thought of dsmantling the instrument panel for the first time, although I can see the theoretical attraction of doing this "only once"!

There must be huge commercial effort going into developing efficient omni-directional LED light sources, since there are so many applications requiring this, not least as a good replacement for the tungsten filament.

[djg]

Ok, John replied to the dashboard part, I didn't get it, I assumed the much simpler window switch illumination (looking back, mentioning dimming should have given it away). Sure, I never really convinced myself to try it, I only thought about the switches now and later, probably, surrogate bulbs like internal lights, map lights, door courtesy lights. In those places, you can use the multi-LED ones without real problems.

Yes, dashboard LEDs are really viable only if the manufacturer designed it that way from scratch. Both from an electrical and an illumination quality point of view. I don't have much trouble with the current setup, either, because as a matter of course, I replace every bulb in bulk when I buy a car and maybe later after a couple of years (the dashboard ones maybe only once but important outer ones get replaced well before they blow). I never had a bulb failing in operation.

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