3157 LEDs in Taillights

[captaincorolla]

I'm thinking of getting 3157 LEDs for my tail lights. I would use them in the brake/parking light position. With a traditional, standard bulb, there are two filaments. How does that work with LEDs? Do separate LEDs light, or do they just light up dimmer? Will I still need a load resistor, since I am not using it with a blinker? Or will I need one, because it's a dual lighting purpose? I noticed a lot of the bulbs on eBay are sold as 3157 OR 3156 application. Shouldn't the two be two different bulbs?

[AlaricD]

Those bulbs aren't going to be very safe or effective, in part due to thermal issues, and in greater part due to the design of the reflector -- the reflector was intended for use with the glowing filament whose size and placement is part of the specification of the 315x bulb. Those LED 315x replacements use multiple emitters pointing in different directions and although it may look like they're doing a decent job, they may actually NOT be.

Also, the major filament (the bright one) in the 3157 puts out 402 lumens. Those multiple LED 3157 LED replacements don't even come close.

That being said, you won't need a load resistor because there is no flasher circuit to accomodate.

[Bitter]

actually there are some barrel style LED bulbs out now that do match the brightness of filament bulbs if you shop carefully. the turn signal LED's i have in my car are as bright as the filament bulbs that were in there. the two brightnesses are accomplished through resistors on the led's circuit board or in some other ones they use a pwm v-reg, but thats usually only for OEM led's.

superbright LED's has a good selection of good bulbs, but the turns i found on ebay on the recommendation of someone else.

[Buurin]

Originally Posted by Bitter

actually there are some barrel style LED bulbs out now that do match the brightness of filament bulbs if you shop carefully. the turn signal LED's i have in my car are as bright as the filament bulbs that were in there. the two brightnesses are accomplished through resistors on the led's circuit board or in some other ones they use a pwm v-reg, but thats usually only for OEM led's.

superbright LED's has a good selection of good bulbs, but the turns i found on ebay on the recommendation of someone else.

Amen.

I bought my LED turns and tail on ebay and they're in use with my car. They are the barrel type and shoots light in all directions. I tested them in night and they're plenty bright.

3157 has two set of contacts so some resistors inside the LED bulb will give you dual brightness. But the 3157 sockets in front and back are wired differently and LED bulbs have to be designed for them. My first pair for some reason have a 555 IC inside and works in both positions. I swaped out all LEDs with amber (they came as red) and put them in front, buying a new cheaper pair for the back which doesn't have the IC.

[gold94corolla]

really? link or pics of this bulb that is bright as filament?

[AlaricD]

Originally Posted by Bitter

actually there are some barrel style LED bulbs out now that do match the brightness of filament bulbs if you shop carefully.

Even if this bulb put out 402 or even 802 lumens, the reflector the bulb is mounted in was designed for a filament of a certain size and position. You might get a lot of light, but it is most likely not in the right place, and could also have too high intensity in places that bring the lights out of compliance.

[Bitter]

Originally Posted by AlaricD

Even if this bulb put out 402 or even 802 lumens, the reflector the bulb is mounted in was designed for a filament of a certain size and position. You might get a lot of light, but it is most likely not in the right place, and could also have too high intensity in places that bring the lights out of compliance.

have you seen a barrel style automotive LED?

You Tube

You Tube

sorry, my cam doesn't like to focus at night. looks like the reflectors are fully lit to me.

http://cgi.ebay.com/ebaymotors/ws/eB...m=120514076555

those are the turn bulbs, as you can see they throw light in perfect 360 deg to the sides AND from the top as well. since they're SMD's there's no focus on the LED light, so they just glow at each point with high intensity.

and these would probably be the 3157's to get, but i'll bet theres ones with higher LED count and more brightness to be found if you look hard and are willing to spend more.


http://www.superbrightleds.com/cgi-b...rake-turn.html

http://www.c5racer.com/catalog/produ...5c5#googlebase
like these, 27 LED's, 21 radial and 6 forward.

[Buurin]

They're still in my car.

[Bitter]

i just ordered some 7443 LED's i ran across on ebay to try in my celica for brake/tail. $16 for the pair, 30 SMD each. if they don't live upto my standards i'll sell them on to someone else to break even and try the 40 SMD ones...but those are $40 for the pair!!!

then onto the rear turns to match the fronts. its nice to see that LED's are coming down in price and up in quality/brightness...now if SSD computer drives would catch up

[AlaricD]

Originally Posted by Bitter

have you seen a barrel style automotive LED?

Yes, and they are crap.

Potentially, and in practice, they can put out too much light in the wrong places (unecessary glare) and not enough light in the right places (potentially unseen or misunderstood signaling).

Pictures don't prove anything. Digital cameras and many film cameras do things with automatic white balance and ISO settings; and film, CMOS or CCD sensors are not the human eye. The only thing that proves anything is a photometric analysis.

[Bitter]

and my eyes tell me that the LED barrel turns i have are as bright as the filament bulbs they replaced and have a much more stand-out color to them. if anything they look brighter at night than the bulbs did since the WHOLE reflector is filled with light, not just a glowing bulb. i mean the bulb did light the reflector but not as completely as the LED does. the bulb had a hot spot where the filament was and the reflector bounced a little other light around. the LED fills the whole section with color/light and creates a larger spot of light at night. in the day its about the same as the filament bulb though, maybe marginally better.


i know the tricks that cameras play, i often exploit those in photo's that i take. however when i shoot lights i always use static exposure and white balance and if possible do direct side by side with both showing in the same shot.

I'm sure that buurin would have no problem putting in one filament bulb and shooting a couple shots to make you happy.

[AlaricD]

Originally Posted by Bitter

and my eyes tell me that the LED barrel turns i have are as bright as the filament bulbs they replaced and have a much more stand-out color to them. if anything they look brighter at night than the bulbs did since the WHOLE reflector is filled with light

Let's revisit that "too much light" thing. The law specifies minimum and maximum intensities at certain points in the beam.

i know the tricks that cameras play, i often exploit those in photo's that i take. however when i shoot lights i always use static exposure and white balance and if possible do direct side by side with both showing in the same shot.

I'm sure that buurin would have no problem putting in one filament bulb and shooting a couple shots to make you happy.

Again, photos do not tell the whole story. A photometric analysis must be done. Not photos, not standing behind it and going "wow, that looks bright" or "that makes me squint more than the old bulbs did".

[Bitter]

oh oh but earlier you said that there was no way that LED's would match the brightness of a filament bulb, so really which is it? not to mention there are some CRAZY bright OEM LED tail lights out currently.

the idea and point behind led tails or brighter tail lights for me is to make the car more noticeable when I'm driving down the road or when i step on the brakes. i want to be SEEN brightly and especially when its foggy or raining.

I really doubt that the barrel LED's are throwing light in THAT much different of a way that they'll be creating hazards and dangers, not like HID lights in halogen housings do.

[AlaricD]

Originally Posted by Bitter

oh oh but earlier you said that there was no way that LED's would match the brightness of a filament bulb, so really which is it? not to mention there are some CRAZY bright OEM LED tail lights out currently.

Even if this bulb put out 402 or even 802 lumens, the reflector the bulb is mounted in was designed for a filament of a certain size and position. You might get a lot of light, but it is most likely not in the right place, and could also have too high intensity in places that bring the lights out of compliance.

I said "if", as you can see.

Once again, the reflector is designed for a filament of a certain size and position. The bulb is not designed to match such a reflector.

Have you checked with Daniel Stern yet? If you don't think I've got enough knowledge on the subject, check with him. If he vets those bulbs, I'll concede to his superior knowledge and education on the subject.

Or go to the CandlePowerForums and post in their automotive lighting section and see if Scheinwerfermann gives those lights his blessing.

[Bitter]

Email sent.