Source For LED Panels (See Design)

Hello, Steve! You wrote on Sat, 29 Oct 2005 21:31:23 GMT:

ST> This is what the rear end looks like: http://216.110.197.146/ltdrear.jpg

ST> I want to install LEDs to do a couple of things. The first is to give ST> the "instant on" look for safety and the second is to reduce the ST> current draw going to the rear of the car when the tail lights are on ST> and you have your foot on the brakes.

ST> I've seen the cheap bayonet replacement LED based 1157s and they suck. ST> Yeah, they are bright and give the LED look, but only in a single spot. ST> You don't have soft diffusion like you do with a filament bulb.

ST> So, I drew up a little blueprint of what I'd like to find for my LTD. ST> Look at my design and tell me if such a board already exists in mass ST> production. (Just don't laugh at the drawings... I'm no architect! ST> lol) If it doesn't exist, I'd be willing to pay someone with soldering ST> skills to create four of these.

ST> http://216.110.197.146/led_design.gif

ST> The drawing is not perfect and the device doesn't need to be exactly ST> like this, but just a flat panel around 3 to 4" high and roughly 6-10" ST> long. I can disassemble my tail lamp housings and fit these panels in ST> there with the LED's facing the diffuser lense and I think it would ST> give an EVENLY DIFFUSED look to both the tail lamp lighting and the ST> lighting when you hit the brakes.

ST> Ideas???

You can buy off the shelf replacements for the 1157's these use a lot less current. It's just got to be easier.

check this link out

With best regards, 3T39. E-mail: snipped-for-privacy@hotmail.com

Hello, 3T39! You wrote to Steve TR on Sat, 29 Oct 2005 22:42:18 +0100:

"You can buy off the shelf replacements for the 1157's"

Sorry, just noticed you already knew this. Dooh! I didn't read the whole post and jumped to the wrong conclusion.

With best regards, 3T39. E-mail: snipped-for-privacy@hotmail.com

Hi Steve...

I'd strongly urge you to check before you install anything other than the original incandescents. I'm very sure that most places we can't change them without "breaking the law"

Take care.

Ken

I appreciate the advice.

I actually already have 2 of these "drop in" bayonet replacements and while they are okay for the "casual user" (lol) I'm quite picky and don't want to look like the rest of the import kiddies with the funky looking LED tail lamps only lighting up in small spots.

I'm willing to spend $$$ for this project so I can get a correct look and it seems a flat panel filling the entire area behind the lense will work wonderfully. Aside from someone's time, I wouldn' think it would be all that expensive... You can buy generic blank PCBs and a box of LEDs and solder away. I just suck at soldering. LOL

I appreciate the advice. As far as the legality of it, well, oh well... I'm not worried with it enough to go look up lighting regulations, but I'm thinking that as long as it lights up in a manner close enough to the original, I'll be okay.

It sure can't be worse than all of the imports/ricers/etc running around with blue/green/red/amber LEDs and those funky "Altezza" tail lamps they think is "so cool."

-Steve

What is the current draw for one 1157 bulb? What is the current draw for 19X5= 95 high output LEDS?

Hello Steve, Not sure if this does exist comercially, but I'll make some up for you if you don't find any from a comercial source. Regards Robert http//notrocketscience.mysite.wanadoo-members.co.uk/

Steve -

I don't know of anywhere that mass produces something like this, but then again I don't really know anything about replacements like this, I just happened to run across your post.

I can see what you want, but I think you will probably need to go through a few prototypes before you get what you want.

I'd recc. you get some breadboard, something like:

or google breadboard and look for something else.

You can then cut the board to the dimensions you need, and start prototyping.

Soldering really isn't that difficult, and this would be an ideal project to learn that skill.

Other than that, maybe post over in sci.electronics.design for some other ideas.

Seems like it might be a fun project, if nothing else.

Good luck,

Matt

Hey, thanks for the advice. I had no idea what to search for to find the (as I was calling it) generic printed circuit boards.

I can solder wires together, but just never have had much luck with soldering components together. maybe I'll buy a bag full of LEDs and see what happens...

Thanks,

-Steve

Yeah, breadboard, perfboard, vectorboard, it's all pretty similar stuff.

Check out here for LEDs, I've gotten some pretty good deals.

Steve,

Glad to help.

Also, google 'how to solder electronics' or something similar, you will find plenty of tutorials to help you get started with the selction of the proper iron and solder, (some even have viddys you can watch) and then it's just practice.

The only other thing I would be concerned with, and it's a minor concern, but I would guess that once you get to a final version you are ready to install, it will be subject to the same corrosion/vibration factors as the bulbs you are replacing; and also you will want the back of the circuit to be well insulated from touching the car frame. I know that the circuit boards in my washer and dryer are sealed in some sort of epoxy to protect them from corrosion, perhaps others can point you in a direction for some sort of epoxy or enclosure to protect the finished product.

Matt

Hey, thanks for the advice. I had no idea what to search for to find the (as I was calling it) generic printed circuit boards.

I can solder wires together, but just never have had much luck with soldering components together. maybe I'll buy a bag full of LEDs and see what happens...

Thanks,

-Steve

If I do come up with some sort of raw circuit board with hundreds of tiny solder joints on the rear, I was going to cover it in a layer of silicone or some sort of nonconductive insulator to help keep moisture out, although these tail lights seal pretty tightly against weather and dust.

We shall see what happens.

Make sure you go for superbrites if you are replacing the lamps. "Ordinary" red LEDs are in the 10-30 mCd range. You should be shopping in the 500+ mCd range. If you get the 10 Cd ones you may end up with something that will blind other motorists at night, but you can always drop the current a little. Each LED will draw about 30-70 mA at around

2V.

You will probably end up wiring them in series-parallel, and you will find in that case that some LEDs are a little more "greedy" than others, and will draw all of the current off, so if you plan to use a series-parallel arrangement, buy extras and then test all of them to match voltages.

If you don't want to be bothered with all of that, you can just use more resistors.

In message , Steve TR writes

OK, here's how you do it.

You take the lens dimensions and create a PCB outline to fit using a PCB CAD program. You then populate the entire area with the pads required for the LEDs and matching series resistors, and connect the pads with tracks to make series multiples of four LEDs and a resistor per circuit across common power bus tracks. Remember to allow for fixings to fit the final PCB into the lens or base, and allow a couple of big pads for attaching the connection wires. If you have multiple circuits then the LEDs can be wired in clusters, possibly with diodes to allow individual or multiple groups to be used from a common switch line.

Now print the finished PCB artwork onto a transparent or translucent medium and expose a piece of photo sensitive PCB material in a suitable UV exposure unit. The PCB can then be developed in an alkaline developer based on Sodium Hydroxide, then rinsed and etched in a hot bath of Ferric Chloride with air being blown through it to cause circulation and agitation of the etchant. Once etched you can then hand drill the several hundred 1mm holes required for the components with a small hand-held drill and then crop the PCB to size and shape before mounting the resistors on the back, cropping the leads at the front and then populating the entire front surface with high output (635nm?) LEDs. If using superflux these are pretty good at self levelling, but 5mm LEDs are best having their anodes soldered first then hand levelled individually before having the cathodes soldered. The choice of resistor value can be calculated as 13.8 - (4*LED-Vf) / LED-I (20mA for

5mm or 50mA for superflux). You can calculate the appropriate power rating for the resistors by multiplying the voltage dropped across them by the current and rounding up to the nearest power rating.

Now simply pop into your lens and bingo, there you go.

--
Clive Mitchell
http:/www.bigclive.com

How about coming up with some off the shelf or homemade diffuser of some kind to snap or attach to the end of the 1157 LED bulbs? Sure it would take more than just spraying some white paint over them but doesn't seem insurmountable... some thick white transluscent plastic lens, clear plastic lens with bunch of metal flakes suspended in it, little piece of foil on tips of the lenses and them white material at base fo lens so light bounces off the lens back onto the white backing, I dunno. How bout just clear lens that spreads the light out like a projector? Maybe once you diffused them perfectly then you'd find out they don't have enough light output anyway.

I've thought of that and might try it.

Because...

The tail lamp assembly already has a fresnel (or is it lenticular?) lens in there. It does a wonderful job of diffusing light when the light source is smack dab in the center of the fresnel lens.

-Steve

Ken, without going into the excruciating detail I've already covered this point on in the past, that is not correct.

DS

The "1157 LED bulbs" don't put out nearly enough total light, period. No diffuser is going to help that.

Email me off the group, I might have something close to what you're looking for and/or need... snipped-for-privacy@ndak.net