Help with LED indicators

[fisherman]

Aloha,

I have a question for you guys and gals. Iam building a carbon fiber dash panel for my truck and I am thinking about using LEDs for the turn signal, hi-beam, 4WD, oil press and fuel press indicators. I have some 8mm LEDs rated @ 6K mcd 3.5v 30-40ma 100ma peak. I was wondering if any of you have done a similar project, and if you could share with me what you ran the LEDS at to take care of having the LEDs bright enough to see in the day yet not blinding at night. Any help would be appreciated.

Ted

 

[TheFire]

I haven't done anything like this, but it looks fun and easy. I'd say install a high/low switch to adjust the brightness for day/night or take the switch directly off your headlight controller.

Also, check the angular output of your lights. You want these lights to be visible from a number of positions, so you're going to have to either aim them at the driver's head, or else get some wide angle ones.

Remember that higher mcd does not necessarily mean more light output, just more light intensity at the hottest spot.

I am pretty sure 15 degree LEDs are probably not suitable for what you need, and I'd be hesitant about 30degrees as well. Look for some wide angle ones, and remember not to be too disappointed about the low number of mcd. It's just a function of the light being spread out more so you can see it. It's no good to you if it's being projected in a pencil thin beam somewhere other than your eyes, right? /ubbthreads/images/graemlins/smile.gif

Another option is to get some led covers. Most devices are made to project a beam of light, where what you want is a diffuser to allow viewing from all angles.

Just my $0.02

Paul

 

[fisherman]

Hey Paul,

Thanks for the recommendations and the education about LEDs. Do you know of a source for the diffuser covers?

Thanks,
Ted

 

[Steelwolf]

If those pencil-thin-beamed LEDs are all you have, there is a way to salvage them for this operation. Use a Dremel or similar to cut off the domed part of the LED, being careful not to cut in to the die or the wire. That will immediately broaden the beam. I like to put a little bevel on the freshly cut corners as well. And if you are using the bare LED as the indicator (instead of putting it behind the cutout colour filter and shape), you might have to "frost" it with some rough sandpaper.

BTW, you mentioned 8mm LEDs? Now those I have not seen before. What is the viewing angle?

 

[Doug Owen]

Some years ago I solved this in a somewhat complex, but workable manner. I returned all the 'grounds' through a pot connected as a rheostat. Otherwise each LED had a resistor in series (value selected for daylight output, that is 'bright'). In normal 'daylight operation, the rheostat was 'shorted out' by a saturated NPN transistor (a 2N3055) which was driven from the 12 Volts from the ignition through a resistor (a dozen ohms or so). When the headlights were also on, a second NPN (base driven from the headlight circuit) from base to emitter on the first 'stole the drive' and put the rheostat back in circuit. You had to adjust the rheostat, but that's to be expected. Attempts to make it 'track' (like by driving off other dash lamps) didn't work out as I recall.

Doug Owen

 

[fisherman]

Thanks for the advice Steelwolf and Doug. To answer wolf's question the viewing angle is about 30 degrees on the 8mm LEDs. I bought a handfull of um from a guy on eBay.

Thanks again
Ted

 

[LED-FX]

>>Do you know of a source for the diffuser covers?<<

Try www.newark.com or www.digikey.com search for LED and hardware or mounting.

Adam

 

[Doug Owen]

[ QUOTE ]
LED-FX said:
>>Do you know of a source for the diffuser covers?<<

Try www.newark.com or www.digikey.com search for LED and hardware or mounting.

Adam


[/ QUOTE ]

Oops, sorry I missed this part. Jameco also carries them, "Cliplite" is the brand name to look for, availble in 3 and 5 mm:

Clipelite LED covers

Red is suggested?

Doug Owen

 

[TheFire]

Looks like you've got several sources there. I like digikey... Post some pictures when you get it all worked out... /ubbthreads/images/graemlins/smile.gif