Afternoony people does anyone have the relectors out of thier headlights that they could accurately measure for me? i vaguely measured it through my h/light lenses at 250mm x 125mm...

Gonna have a word with the engineering company monday if i remember but wanted accurate measurements.

evening all...
STILL not managed to get hold of the engineering company
altho... Im still collecting bits and bobs slowly, very slowly. Our drivers just aren't breaking as many trucks as they used to... BUT today i hit the jackpot, Volvo decided to put LED repeaters on their trucks from late 58 plates onwards. When stripped out theres a convenient PCB and lens arrangement that fills roughly half of the cinqs front indicator lens.

...PERFECT...

...ish! The problem is HGVs run 24v electrical systems, usually, generic LED units are compatable with 12/24v but ive found that manufacturer specific units are tailored to 24v. There is a bank of 6 160ohm resistors they run between the LEDs on the PCB a pic is up on my flickr (richydraper1) can anyone 'hook a brother up' and advise what value resistors should i be using in place of these 160 ohm resistors for a 12v system?

By the way for all of you that are interested theres a pic of a Mercedes Petronas GP hospitality outfit on flickr too (we service and MOT their fleet of trailers)

untill next time keep it shiney side up

richydraper said:

By the way for all of you that are interested theres a pic of a Mercedes Petronas GP hospitality outfit on flickr too (we service and MOT their fleet of trailers)

Click to expand...

There are two of those and none of the indicators

Sorted

doh, I was expecting that to just be:
+24v -> resistor and LEDs (x6, in parallel) -> ground

Instead you seem to have that plus a bunch of transistors, diodes, etc plus an IC. Perhaps it's all onboard power regulation, so it appears an even brightness with or without the alternator running or just so the LEDs don't get overloaded and burn out.

You could try swapping stuff but it might be easier to just use that PCB as a carrier for the LEDs - hook up a lorry battery and see how much one LED is being supplied with, then strip the other components from the back and wire the LEDs up in series (or four banks of three LEDs in series, in parallel) with some resistors so they won't receive more than the original voltage when the unit is supplied with 14.5v (Cinq alternator running).

Typical Volvo that is buddy they stopped believeing in the battery --> switch --> bulb --> ground thing along time ago! Now its battery --> control unit --> ecu --> bulb --> back to ecu... the wiring diagram for trucks is about 250 pages iirc.

anyway... i hear what your saying... but these things do illuminate at 12v but its significantly less than if you feed them 24v. thats what makes me think it would just be a resistor change. i dont know if the ICs would just be stabilising any voltage given to it or limiting voltage. the fact that all the resistors are 160ohm makes me think the banks might be fed seperately (so if one fails the rest wont).

ill have to do a bit more messing about with them

yea yea!!...right then, i am in the middle of putting together a guide on dash conversions... atm its a 10Mb word document but i gotta do some image tweaking to get that size down... haven't got an ETA on that at the moment tho but its in progress.

ive had another idea about rear light fabrication. :slayer:

sacrifice my old set of rear lights for a mould/pattern. plaster of paris the inside of it to get an internal mould then flat back the fresnell lens 'dimples' out of it. put it in the oven at about 170*-180* and lay my tinted perspex over it.

i had some headaches thinking of how i could get the right level of light diffusion on the LEDs... had another brain wave. i wanna mount the LEDs initially in blu-tak then make a frame from something (wood or 20gauge steel cos i have loads of it readily available) shrink wrap the frame like you would a cake tin with greaseproof paper and use translucent silicone sealant as both a mounting media and diffuser. it seemed like a good idea as i could add layers to it to get more diffusion if needed

then instead of using a PCB for power feeds i would link the LEDs together with single core wire stripped of its insulation and solder onto each terminal then waterproof with silicone or possibly expanding foam and wire in the original terminal from the sacrificed light and superglue/silicone (yes i know yet more silicone) it all together...

how do you like those onions!!

Couldn't you just bend the LED legs over and solder them together for most of the joins?

Also making a PCB on the 'puter and printing/etching it, then soldering on SMD LEDs would be harder but look neater and line up dead straight. Unless you have access to a bench press or some other suitable tools, which could clamp the frame, allowing you to measure up and move it by exact amounts the holes you're currently thinking of doing might end up *just* not lining up by a tiny bit, just enough to be annoying.

the LEDs are 'pre-enjoyed' so they only have stubby legs hence why i was going the single core route.

yet again, as always dan, good point about uniformaty of the LEDs.
I thought about this a little bit an came to the conclusion that if i get them close enough together the translucent silcone i wanted to use would give such a heavy diffusion that it wouldnt be an issue. In addition to that, the plan to put it behind tinted PMMA. i feel it would be a such a miniscule flaw that i personally dont think its worth worrying about or trying to work around.
Im going to try a sample with a handfull of LEDs (about the size of one cell on the rear lights) and this should give me an idea of if this technique is good or not. and what sort of effect it is going to give etc etc.

Ah I see. I was thinking of the newer BMWs with the LEDs lined up in neat little rows, but there is far less diffusion (if any) on those.

i met the guy from the fabrication company today (FINALLY) told him what i want for the h/light mounting plates so im gonna wait and see what he come back with. dunno about price yet i did enquire 'bout a backhander (*whispers* i dont think they like doing backhanders!) so im gonna be recieving 2x 2mm plates to fit my twin projector units into at some point.