LED number plate light from CovKid

Website · Post by **CovKid** » 15 Jul 2008, 18:45

Heres a project for anyone considering going over to LEDs (Light Emitting Diodes) for running lights.

Firstly, the brightness of LEDS (light emitting diodes) has come on in leaps and bounds over the last year or so and the light emitted, whilst no substitute for halogen bulbs in headlights, is certainly a great substitute for most other bulbs around a T25, if not a distict improvement. They also consume much less power (just milliwatts compared to watts), a consideration if you need to leave some lights on in the dark (ie a breakdown) and give a clearer, whiter colour.

Now, most bulbs can be replaced for compact LED arrays on ordinary bulb type fittings or festoon type arrangements. Ebay is already awash with these, ready made, and some might find these do the job. Typically they are 19 LEDS crammed together for indicators, brake lights etc. The one thing NOT so good about LEDs is they tend to be very directional compared to the 'all round' glow of an ordinary bulb. However, tungsten bulbs lose some light as well as an enormous amount of heat - in fact they are not very efficient at all.

Lets consider the number plate light.

The number plate light on a T25 is actually two units, each supporting (or boasting as it might have been described in the VW brochure) 2 x 5watt bulbs. They're not bad I guess, but the bulbs will ultimately go and usually after they've already become blackened. I decided to keep the original plastic lenses for these to afford some protection from rain and washing the vehicle. I could have replaced the bulb with a ready-made LED equivalent but I wanted a better spread of light so opted for 4 LEDs per unit, soldered on to veroboard with 450ohm resistors for each LED. Without resistors they will die within seconds at 12v since most LEDs are around 3-3.5v I could also have made one single, long unit to replace both but wanted to keep the original look as far as possible.

I used 8 x Ultra-bright white LEDs (try Ebay for these) and 8 resistors and a small piece of veroboard.

Basically all I did was fix all the components, shape and fit the veroboard to fit the housing then soldered two male tags on the back so I could just connect to the existing wires. The original light comprises a plastic box, a rubber seal and a bulb fitting. All I did was dump the bulb fitting. I won't go into the exact circuit since its so simple and theres a link further down this post showing layouts you could use. The long lead on LEDs is the positive by the way.

I made a new new flat unit from plain, blank veroboard, using the original bulb holder as a size guide and rounded the corners with nippers and a file. Next I made 8 fine holes enough to poke the leads from each LED through, plus a hole either end so that the lens retaining screws went through these too. Most LEDs have one lead that is longer - this is the positive side and should therefore be powered by the + side of 12v. Since conventional LEDS are typically 3.5V each, 12v would blow them straight away so you fit a 450 ohm resister to the + lead to take up the extra voltage. Once everything is soldered in place, you only have to 'splay' the LEDs slightly to spread the light pattern a little, connect, refit the screws and away you go. Chances are, the vehicle would have long since rotted away or the supply of fuel dried up before the little suckers ever blow.

The light is far better and should I ever leave my lights on accidentally, it will make little odds since my side and tail lights are also LEDs and draw milliamps compared to the old bulbs.

Someone out there could do a neater job than I've done I'm sure, but hopefully my rough explanation will be some help to anyone considering doing this. Cutting tracks is easily done with an 8mm drill bit by hand. You certainly want to ensure that the ends of each board which take the screws, are cut off from the rest otherwise you might short part of the circuit. Some may be able to make their own custom boards. I'm told this is possible using a laser printer and the right paper, but veroboard is ok.

Incidentally, the last photo was taken in broad daylight and we all know how 'yellow' the ordinary bulbs are.

For reference, I found this page really useful for calculating correct resistor, how many etc: http://led.linear1.org/led.wiz - you just need the specs for the LED type you're using to input the required info.

[img:601:599]https://club8090.co.uk/wiki/images/thumb ... eplace.jpg[/img]

Next project is to convert the rear light housings to LED arrays (ie whole boards crammed with them). Again, it is dooable but I think I'll need to print a complete layout for this and you'll need to cut part of the plastic on the rear of the light unit to get these lights in square, but hopefully I can do mine before the Autumn and pass on the info.

I may be able to supply these at reasonable cost in kit form with a specially made circuit board - will look into it!

Post by **gsmoke** » 15 Jul 2008, 19:20

What a great posting.
You've given me some inspiration there.
Will be visiting Maplins tomorrow!

Website · Post by **CovKid** » 15 Jul 2008, 19:24

Nooooooooooo! Maplins charge WAY WAY too much for these bits. Around £1.20 for ONE LED compared to 50 for around £3.70 on Ebay.

Buy the LEDs on Ebay - they often come with resistors too. The above would be much better on etched custom board by the way - less fiddly but veroboard cheaper certainly.

Post by **Titus A Duxass** » 16 Jul 2008, 05:43

Nice job.
I have seen LED replacement bulbs for the rear lights and indicators, they are built in the same way, a board with a cluster of LEDs which is then attached to a bulb type bayonet fitting.

It would be interesting to find out the difference in power requirements between a complete LED set up and a normal tungsten bulb set up.

Just for information, the resistor does not control the voltage to the LED.
It is there to limit the current flow through the device.

LEDs will work with any voltage as long as there is a diffential of 1.8v across the device. Its like a relief valve.
Once the pressure gets over 1.8 water (current) flows through the device).

Obivously, if you have 12v connected across the LED then the valve will be fully open, so you have to limit the amount of water (current) that flows with a resistor.

Post by **ringo** » 16 Jul 2008, 07:51

Another great post CovKid - keep it up!

Thanks

Ringo

Post by **ermie571** » 16 Jul 2008, 08:09

E-bay...here I come.

And Covkid....many thanks! I am going LED in the van - inside and out hiopefully....so a bit of basic understanding like that is REALLY useful.

I can see a sticky coming on....LEDs !

Em
x

Website · Post by **CovKid** » 16 Jul 2008, 11:14

I guess I'm obcessed with LEDs through running my battery down too often. The ideal way to drive LEDs is with a LED driver since they run even more efficiently than using a resistor then, but its more of an expensive outlay and a bit more complex in terms of a circuit.

Been looking at rear light clusters and it definately needs a proper printed circuit board to allow the attachment of the tags for the rear light plug, and a fair bit of testing to get the brightness right but I'll give it a go and see if I can develop a PCB that would do the job. The route I want to go is creating a bank of LEDs per unit rather than a ready-made LED adapted bulb but the costs may be too great. We'll see.

Other things you have to consider are indicators. The lower load of LEDs means a conventional flasher won't work unless you solder in more resistors across the bulbs (counter productive) or buy a flasher unit for this purpose.

I have though, tried this fairly successfully with very small sidelights (ie bulbs in headlights):

[img:640:518]https://club8090.co.uk/wiki/images/Ledbulb.jpg[/img]

You have to smash the bulb, churn out inards with a screwdriver and solder a suitable resistor and 10mm ultra-bright LED into the body. Fiddly but around 50p a go max. This one is unfinished since it lacks the final seal of epoxy resin but you get the idea. Also worth noting that the reduction in power consumption can have slight side-effects. Opening a door which by turning on an interior light would normally trigger an alarm (if you have one fitted) no longer applies because the alarm can't sense such a minor event. Also, most LEDS have a limited light spread, typically from 30 degrees to 60 degrees depending on type used so can be fairly directional.

Website · Post by **CovKid** » 16 Jul 2008, 11:25

For reference in case anyone hasn't seen commercially available LED replacements, heres two:

[img:388:383]https://club8090.co.uk/wiki/images/Ledcon.jpg[/img]

There are combined stop/tail types as well as indicator replacements but note what I said about flasher units.

And 'Titus A Duxass!, you're quite right, the resistors do limit the current flow. LEDs actually shift their requirements somewhat as they warm up and the resistor is there as a kind of shunt really. In theory you could wire up LEDs in series without a resistor, but it doesn't work well, and often not for long! This is why I'm wondering on something as big as a large board full of them, proper LED drivers might be a better way to do it rather than soldering so many resistors.

Post by **Titus A Duxass** » 16 Jul 2008, 11:37

You can get "ready-made" LED rear light units -
http://www.lion-tuning.de/index3.php?pa ... opid=44342

But that would take the fun out of it.

How are you going to construct a combined rear/brake light?

Remember that legally (AFIR) - you need 5w for the rear light and 21w for the brake light.
Would a centre cluster of say 6 super bright LEDs surrounded by a ring of normal bright LEDs produce the required light intensities?

Website · Post by **CovKid** » 16 Jul 2008, 11:43

Yes, could do it that way or just use LEDS with different light ratings for each?

You don't have to have them combined though. My light cluster would allow me to put the brake light in another compartment which is still legal - I checked.

With regards to the ready made T25 LED units, are they just fitted with LED bulbs or is it a complete redesign? If the latter, I probably won't bother making one

Post by **Titus A Duxass** » 16 Jul 2008, 11:54

I have no details about the light units, I would guess that they have been retrofitted with LEDs. I will see if I can find more information.

Post by **Titus A Duxass** » 16 Jul 2008, 11:57

Okay, from what I can gather they are a direct replacement for the originals with LED instead normal bulb.
They are plug and play with original bus/van wiring.

Not a bad price either at 84 euro + pnp.

Post by **airhead** » 16 Jul 2008, 12:08

For indicators, you can get a heavy duty flasher unit which will flash at the same speed regardless of load. I have one in my MG cause the indicators were always having a mickey fit and it sorted the problem out. €12 at halfords. Its their own brand 3 pin one.

Post by **billy739** » 16 Jul 2008, 20:20

i have made some LED lamps for the rear of my van
basically by inserting some trailor lamps into the rear lenses.

this gives stop and tail led operation
normal bulbs (led replacments) fitted to the other lamps .
fog lamp has been moved to side lamp and i have also inserted some position lamps in the outer part of the lamp.

will sort some pics.....

Post by **T'Onion** » 16 Jul 2008, 21:52

Cov
if your making some of the led no. plate lights , i'd be up for a set