Author Topic: Led Auto bulbs (Read 3995 times)

Demetri · « **on:** May 17, 2003, 06:55:03 PM »

Well, this is my first diary post, and I'm putting it here because it doesn't belong anywhere else, and I'd like to pick the brains of the knowledgeable people who frequent this board. I've been looking around, and I can get some pretty cheesy led bulbs from Autozone for $15 or so for two, but I've seen them in operation and don't consider them adaquate. Then I've found some good ones at ledtronics.com, but at $50 per bulb($100 for two), I'm a tad sticker-shocked. I have more time than money, and am certain I can build something similar for less money, as I can get super bright red led's for a buck each. The charging system on my truck runs at 14.7 volts. If I run 4 led's in series, with a 3.6 volt drop per led, that gives me 14.4 volts, and I don't think the extra current that .3 volts will push would hurt much at all. I could also use the 7812 chip mentioned on the led page of Otherpower.com to regulate to 12 volts even, and slightly under-power four led's in series. This would probably be the best way, as the led's wouldn't get dim when the engine is off. I have to look into how much amperage the 7812 chip will handle, the lifespan, the heat produced, the efficiency, and shock resistance. I'm thinking, if heat dissipation won't be a problem, of encasing the whole thing in hot glue or epoxy. Experimentation will tell, though. Anyone with experience, suggestions, or criticisms please let me know.

Demetri

P.S. The guy at the electronics shop was telling me about a red led he can get that will blind a person at three blocks away. It costs about $20 and draws about 1/3 of an amp. Hmmmmm........

kurt · « **Reply #1 on:** May 18, 2003, 12:01:24 AM »

http://www.mitedu.freeserve.co.uk/Circuits/Power/lm317.htm

TomW · « **Reply #2 on:** May 18, 2003, 03:39:15 AM »

Demetri;

Just curious why you want LED lights on what I assume is a gas powered vehicle?

Seems like this was discussed on the old board some and unless you are running an electric or hybrid vehicle it would not gain much fuel savings. At current prices here you would need to save around 35+ gallons of gasoline to repay the $50 pricetag on the one LED you mentioned.

Maybe you have other reasons for doing it?

Cheers.

TomW

kurt · « **Reply #3 on:** May 18, 2003, 03:44:03 AM »

http://www.otherpower.com/otherpower_lighting_flashlites.html

http://www.uoguelph.ca/~antoon/

http://www.otherpower.com/cgi-bin/webbbs/webbbs_config.pl?read=10803

http://www.otherpower.com/cgi-bin/webbbs/webbbs_config.pl?read=10678

http://www.otherpower.com/cgi-bin/webbbs/webbbs_config.pl?read=9863

http://www.netcentral.co.uk/satcure/design/ledflas.htm

Demetri · « **Reply #4 on:** May 18, 2003, 10:03:50 AM »

Kurt- Thank you for those links, they were great help.

TomW- I'm installing led's for many reasons. I occasionally have to let my truck sit for long periods of time with the parking lights on; the advantage of led's there is obvious. I like the fast turn-on time of led's. I heard that led's give 17.5 feet of extra reaction time at 60 mph when compared to incandescents. As we both know, car crashes are escaped by miliseconds and fractions of an inch, and 17.5 extra feet sure sounds nice. Then there's the maintenence issue. Install and forget, no more burned out bulbs. The shock resistence comes to mind too. Occasionally I transit gravel roads and fields at excessive(insane) speeds, and have destroyed more than one bulb doing so. Headlights get expensive......

Demetri

TomW · « **Reply #5 on:** May 18, 2003, 11:49:02 AM »

Demetri;

Sounds like good reasons to try them out. Nothing quite as much fun as returning to your vehicle and discovering a flat starting battery.. after the ride has left.

Cheers.

TomW

Demetri · « **Reply #6 on:** May 18, 2003, 11:34:30 PM »

No kidding Tom. Ever push start a truck by yourself?

I'm working on adding a deep cycle battery to power the parking lights, cb, stereo, and maybe a couple other goodies. The truck is an '87 Dodge Dakota, currently powered by a 3.9 liter v-6(working on a 360). I have a 100 amp alternator out of a Caddy with power everything. Someone said they wanted to know how the alternator conversion went, I think on the old board. It was pretty straight forward, keep some scrap metal around to make brackets with, a BMFH or two, extra bolts, all the usual. I don't have a/c, so there's an idler pulley up top. I might put a compressor in for the air, but I doubt it, I don't want to carry the weight and have to move the extra mass when I don't need to. A dual belt pulley is needed on the alternator. I ran 4 gauge wire to the battery on the opposite side of the engine compartment. Anyone who has one of these, do yourself a favor, pull apart the wiring harness past the battery and chop out all the fused links. Mid '90s F*rds have great fuse boxes in the engine compartment to replace the fused links with. They use the new Maxi blade fuses, huge contacts on them(Anyone seen the miniature fuses? I'm not going to run 30 amps through contacts that size.) If a fuse blows, it's easy to replace, and this box makes a great place to add other accessories. I also fused the mains running into the fuse block in the cab. Whoops, this post is waaaaaayyyyy off subject and getting long. Oh well, what diaries are for.

Demetri.

P.S. A two barrel carburetor off of an early-late 70's(without the emissions junk) small block Chrysler/Plymouth/Dodge will bolt right up. The distributor from the same years(without the leanfire junk)is also easy to switch over, two roll pins on the reluctor and the cap. That does away with the computer controls(and eliminates about six lbs of wire and vacuum lines); with such modifications, these motors can scream. Don't let the EPA catch you.

12volt dan · « **Reply #7 on:** May 25, 2003, 09:15:04 AM »

Your right about LED`s being safer than ordinary bulbs. A lot of truckers are useing them up here (northen Can) for that reason. Also the low draw and the long life.

I use them (white light) for outdoor lighting and am impressed by the amount of light. I`ve also been "blinded" while following trucks. keeps the tailgaters off your ass

ToddH · « **Reply #8 on:** May 26, 2003, 03:40:59 AM »

You might take a look at this site....

http://www.superbrightleds.com/led_prods.htm

I haven't ordered anything from them yet but I am thinking about getting a few of the white LED bulbs to use as task lighting in my house (MR16-W & 1156-W19). They certainly have a large selection of LEDs to choose from.
Prices seem real good too.

12volt dan · « **Reply #9 on:** May 26, 2003, 04:50:42 PM »

I ordered 4 mr 16`s and at least got them without being riped-off. they seem to be an ok supplier.

nice bright light!

Demetri · « **Reply #10 on:** May 29, 2003, 07:07:42 PM »

Been going slow, had a lot of other stuff going on. Just got back from the electronics shop, bought some 7812 chips. They're the size and shape of mofsets, with a metal case for heat-sinking and two terminals out the back; rated for one amp. I'm certain that the metal case is the negative terminal, but I don't know which of the terminals sticking out the back are input or output. Will it fry anything if I hook it up wrong for a sec? I'm thinking not, but I want to make sure. Thank you all.

Demetri

TomW · « **Reply #11 on:** May 30, 2003, 01:10:41 AM »

Top return out of 6,000 from Google.com for 7812 data sheet had the info:

http://us.st.com/stonline/books/pdf/docs/2143.pdf

Learn to use google it is very effective for many questions I have had. Free, quick and easy.

Cheers.

TomW

Demetri · « **Reply #12 on:** May 30, 2003, 10:21:30 AM »

Thank you Tom, I had been Googling for "7812 specifications" and "7812 technical information." Much appreciated.

Demetri

Demetri · « **Reply #13 on:** June 18, 2003, 01:03:46 AM »

Finally had time to do some more tinkering. Got my 7812 all hooked up, got four led's in series hooked up, flipped the switch. Led's lit! For about 1/3 of a second, when they all went out. Individual testing finds them all toast. Good thing I only used four! Would have seriously sucked to hook up $25 worth of led's and fry them all. Now, what happened? I'm thinking that one or two led's weren't stopping their full rated voltage, which made the rest absorb more, which could have easily given them several times their rated current. But, as is obvious, I am no electronics expert. I am thinking I'll need to find/build a 3 volt regulator and wire all of the led's in parallel. I may buy some of the Autozone led bulbs and reverse engineer them, depending on what my research reveals. $15 is a lot of led's. Again, thank you all.

Demetri

TomW · « **Reply #14 on:** June 18, 2003, 11:19:44 AM »

Demetri;

Have you seen this product on Forcefields site?

http://www.wondermagnets.com/cgi-bin/edatcat/WMSstore.pl?user_action=detail&catalogno=2110

$12 ready to install with 12 LeDs in it runs off 12V too.

12-LED White Cluster Lamp, 12VDC, Bayonet Base

Cheers.

TomW

Demetri · « **Reply #15 on:** June 18, 2003, 11:40:07 AM »

No Tom, I hadn't seen that, thanks though. It looks very similar to the Autozone bulbs, and at $12 each I can still build the same thing, even with white led's, cheaper. I'm seriously thinking of just eating the cost and spending the $50 a bulb to get what I want. Sometimes you just have to do that. Thanks for your help, Tom.

Demetri

jubalearly · « **Reply #16 on:** June 24, 2003, 01:32:09 PM »

Demetri, I've found that a small resistor is a good idea to prevent thermal runaway in LED's, even when the LED forward voltage EXCEEDS the applied voltage. A 10 or 20 ohm resistor won't cost you much voltage drop (30ma max current). You might try a 320 or 470 ohm resistor & see how much effect it has on brightness if you really want to make sure current is less than 30ma. I've found that these diodes usually don't fail until you get over 100ma, although I limit the max to 50ma. - excess heat will shorten the life.

And are you sure 14.7v is the max voltage on your system? Even if that is the maximum steady state voltage, you may have occasional spikes above that - cars are a noisy environment. Also, I use 7815's for my auto voltage (13.5 - 15.0v) projects. The last lot I got actually regulated to 14.6v, so I could use one diode on the output (or input, depending on use)to protect against reverse connections and get 13.5-13.9v. If you want more than 12v from your 7812, then you can put a diode in the ground (negative) and raise your output by .6v per diode

Demetri · « **Reply #17 on:** June 26, 2003, 12:41:56 AM »

You're right Jubalearly, I probably should have included a resistor. The truck wasn't running at the time, and there are no relays in use, I know they produce a dangerous high voltage back feed when they turn off. Yes, I'm certain that 14.7 volts is as high as it goes, and I had measured my 7812 chip at 12.34 volts. 3.6 volts x 4 = 14.4 volts. The led's should have been fine. I'll keep tinkering with it, eventually. I bought some 194 led "bulbs" for my side markers, and am trying to figure out how to get them to flash with the turn signals when the running lights are off. The normal incandescent side marker is hooked to the positive front running light and the positive turn signal wire. When the running lights are on, the side marker picks up positive from it's connection to the running light wire, and grounds through the turn signal filament. When the turn signal is turned on, the side marker gets positive on both terminals, and goes out. When the running lights are off, the side marker lights get power from their connection to the turn signal and ground through the front running light filament. However, led's are polarity sensitive! So they don't flash when the running lights are off. Not a huge problem as my headlights and running lights are on whenever I'm driving, day or night, good weather or bad, but it's annoying none the less. I've been trying to figure out how to create the effect I want with relays, but I'm just not getting it. Anyone know of a circuit diagram or better way of doing this? I'd like to get away from relays, both because of the high power back feed and because they're just plain more crap to go wrong. The reliability of a system is(generally) inversely proportional to the number of components it contains, on top of being only as reliable as it's most unreliable component. Thanks Jubalearly, thanks again, everyone else.

Demetri

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