Would the scheme I've been suggesting work?

I suppose it could. A constant current scheme would be better.

I suspect a regulator will be needed, but it may have been a good idea in any case.

With a constant current scheme, a regulator shouldn't be necessary.

 

Right now I don't have any LEDs but the ones in the picture above so I am willing to buy. I didn't buy anything yet, as I was unsure of which MCD to get or degree of beam.

The trouble with buying from online auctions or non-authorized distributors is that they don't have a reputation to uphold, so they can make ridiculous claims on performance vs price. But tail, brake and turn signal lights aren't something to treat in a casual manner - your safety and your passengers' safety are at stake.

The LEDs from Digikey I posted a link to are really quite bright, but I don't have a good way to make a comparison (or calculation) between how much light will be emitted through your lens with "x" number of LEDs vs how much light is currently being emitted using your standard incandescent taillamp bulbs.

One way you might do that is to use a photoresistor (CdS sensor) and an ohmmeter in a dark room, first powering (a) standard bulb(s) with 13.8v, and then several of those LEDs with about 65mA each, both shining through the taillight lens. When the light intensity is the same at a given distance from the lens, you'll get the same resistance reading.

Radio Shack used to sell a variety pack of CdS cells, 5 in a pack, for a couple of dollars. They'd work fine for this purpose. You don't really care about the absolute value of light, just relative to what the standard lightbulbs will supply.

However from this 2 days I have learned ALOT!!! You guys are genius's compared to me.

We've been at this a few days longer than you have

Since the superflux LEDs have 4 pins, how would you connect them? From seeing the data sheet I see there are 2 + and 2 -. Would that mean I could connect only 1 + and neg connection for the tails and then use the other anode and cathode for a separate brake circuit making the tail light be twice as bright?

There's just one LED per package. The four mounting leads makes them a much more rugged unit than the 3mm or 5mm two-lead LEDs, and they can dissipate more heat via the leads.

I was also thinking about using SMD LEDs being as they are small in size, but I've never used them before and didn't want to buy so many and have them not work out correctly. However, after getting advice from here, I can feel confident that I can buy enough of ANY kind of LED to light up a landing strip at an airport.

You really don't want to deal with SMT/SMD LEDs if you can avoid it; they're far more expensive, far lower power, and very difficult for a novice to solder. Thru-hole is much easier to deal with.

BTW, runway 3L at MCAS Yuma, Arizona is 13,300 feet long and 200 feet wide. That'll take one heck of a lot of LEDs to light up!

 

I added some pics of the reverse lights in blue. This was an old project I had done a LOOOOOOONG time ago. It was a quick Simple project I was going to do for interior brightness, but after I put it all together realized that there was no possible way I could mount the board anywhere bc I cut the board too small and filled it all completely with LEDs. I can't remember which LEDs I used, but they came from besthongkong seller on EBAY.

Tonight I used a Ryobi 18V drill battery to light these. I didn't use any resistors bc the circuit was originally designed for a 12V application. After having these on for 2 minutes I could smell them starting to burn out and they got quite warm. I ended up burning out at least 4 of the LEDs. OOPS.

 

LEDs aren't fond of overcurrents. Even though most of them may still be working, they'll have a very short lifespan now. Time to replace them with white LEDs.

 

I also made the same circuit at the same time using white LEDs. Here are pics of the white LEDs in the taillight area. It looks good in the red lens, but horrible in the amber turn signal lens. My fix for that....get transparent red spray paint and make it red. BTW I've already done that to my current lens and it looks sooooooooooo much better even with the stock bulbs. The circuit is 24 LEDs. They are pretty bright!!


Do they make any sockets that I would be able to buy this way i dont have to A> chop off the original socket or B> tap into it.

 

Those lights if the same as my car have indeed two post. one is for tail light the other is for brakes. it seems to me that breaking one lamp and temporarily adding LEDS in series parallel can solve your problem of how, what to do. A $2 dollar loss I guess. LEDS comes in all kinds of sizes, current, voltage drop, emissions & angles ,spectrum and finaly angles. It would be unwise to do it without testing if it is to bright ticket if dims accident. take your pick.

 

Can't emphasize what Wookie said about overcurrents enough, LEDs must have a current limiting resistor, always.

You can build simple regulators that allow a range of voltages such as a car, but in the end it always involves a resistor in the circuit.

It is pretty simple to calculate. Want to go through the exercize?

 

It is far better to pulse or duty cycle the LED lights on/off rapidly than have them burning full intesity continuously. This will require a "driver" to drive the LED's to change the intensity better known as PWM pulse width modulation. 12-14 volts are applied to both filaments of the 1157 bulb, the resistance is in the bulb itself thus changing the brightness of tail vs brake lights. If you simply wish to replace your current 1157 bulb with LED lights then may I suggest this link
http://www.xtralights.com/index.asp?PageAction=VIEWPROD&ProdID=252
simple, easy pop in place using your existing socket an less than 5 bucks

 

There is nothing special about PWM for these types of circuits. You get the same results by increasing the value of the resistor, and I don't think the OP is ready for unnecessary complexity. PWM allows you to vary the intensity remotely, and that's pretty much it.

The only reason any regulator is needed is because a car varies between 12VDC and 13.7VDC. When you use 3 diodes in series it gives you 1.5V to 3.2V to play with, which is a pretty high variation.

If you reread the original post he is trying to avoid buying new parts for a fender bender.

Interesting part though, I'll say that.

 

Just a note on "brightness" control. The cars in the United States that I have observed with LED tail lights pulsed the lights at about a 50% duty cycle (maybe a little less) when in "tail light only mode", and when the brakes went on or the turn signal flashed, the duty cycle went to 100%, thus changing the apparent brightness. The pulse frequency appears to range from about 1 kHz to a few kHz.

You can see this yourself the next time you follow a car with LED tail lights at night. Scan your eyes left and right and notice the pattern of dots on your retina. The ratio of bright to dark is close to the duty cycle of the LEDs (your retina has become analogous to a oscilloscope screen). When the pattern becomes a solid streak, the LEDs are at 100% duty cycle. The farther away you are from the car, the easier this is to see.

Duty cycle modulation means that you only have to have one power switch. It also means that you can use an inductor in series with the switch to limit current instead of a resistor.

 

Just a note on "brightness" control. The cars in the United States that I have observed with LED tail lights pulsed the lights at about a 50% duty cycle (maybe a little less) when in "tail light only mode", and when the brakes went on or the turn signal flashed, the duty cycle went to 100%, thus changing the apparent brightness. The pulse frequency appears to range from about 1 kHz to a few kHz.

You can see this yourself the next time you follow a car with LED tail lights at night. Scan your eyes left and right and notice the pattern of dots on your retina. The ratio of bright to dark is close to the duty cycle of the LEDs (your retina has become analogous to a oscilloscope screen). When the pattern becomes a solid streak, the LEDs are at 100% duty cycle. The farther away you are from the car, the easier this is to see.

Duty cycle modulation means that you only have to have one power switch. It also means that you can use an inductor in series with the switch to limit current instead of a resistor.

Resistors are a lot cheaper and simplier. Remember, we are talking to a noob. In this case simplier is better, and it doesn't take much to light an LED. I may be mistaken, but I think the arrangement is a twin filiment type, or two bulb type. The variable brightness is build in.

 

Here is a simple solution to variable battery voltage issues.

All resistors are ¼W. The variation of the zeners could be a problem, since the low end tolerance is 11.4V (1N4742A).

 

$5.99 each is cheaper than buying the components to build yourself. It is simple to plug in to existing socket and it is done. No PWM, No voltage drops to calculate, No current limiting, yada yada yada. Plug it in and GO!
You have your LED lights and it is cheap! How complex is that?

 

There are led taillights one can get for cars!(in the aftermarket) Look in the jc whitney cat. and you will find them for about $30usd a piece. They even move!(in a way) Robbie in wyoming

 

$5.99 each is cheaper than buying the components to build yourself. It is simple to plug in to existing socket and it is done. No PWM, No voltage drops to calculate, No current limiting, yada yada yada. Plug it in and GO!
You have your LED lights and it is cheap! How complex is that?

This assumes an upgrade, not a repair. You need to reread the OP.

 

$5.99 each is cheaper than buying the components to build yourself. It is simple to plug in to existing socket and it is done. No PWM, No voltage drops to calculate, No current limiting, yada yada yada. Plug it in and GO!
You have your LED lights and it is cheap! How complex is that?

I tried these once. The replacement LED bulbs don't put out as much light inside the taillight. IE the incandescent bulb will light up the entire lens where the LED bulbs are more of a small circle of light. That is why I want to design my own board so I can light up the entire lens. I know I can get the spider bulbs which expand inside the taillight, but I would need 4 of them altogether and those bulbs aren't cheap by any means!!



Correct, the bulbs are 2057 which are dual filament bulbs. Inside the taillight are 4 bulbs. one for reverse (2057 bulb which is dual filament), one for signal (1156 bulb which is single filament), and 2 for brake/tail bulbs
(2057 bulb which is dual filament). Odd I just now realize that the Reverse lights are dual filament......why is that?! They only come on when in reverse and have no other function



Bill....What does CR1 and CR2 mean? Is that the car's 12V ground lead? What in the world is a zener?!?! What do the squiggly lines represent next to the diode symbol of the LEDs? Does that mean variable volt source? Looking at your diagram...does it mean that the 100 ohm resistor goes from lead 1 and 2 of 2n2219a and the third lead is for the LEDs?

 

CR1 and CR2 are Zener diodes with a breakdown rating of 12v. They're named after Clarence Zener, who discovered the reverse breakdown phenomenon of this particular type of diode.
http://en.wikipedia.org/wiki/Zener_diode

I prefer to use a reference designator of ZDn when a Zener diode is being referred to. CRn is sort of an old-fashioned reference designator; once widely used but has fallen out of favor.

The squiggly line through the diode symbol is typical of what a Zener symbol looks like; Schottky diode symbols look even sqigglier; the line is turned into a squared-off "S".

 

Zeners conduct if the back bias exceeds their zener voltage. Here is a zener diode, a Schottky diode, and a zener diode circuit. They make good voltage regulators.

What can I say, I'm an old fashioned sort of guy.

 

You might have a heat problem if you make your own car rear lights.
I was recently given many Luxeon Lumileds. I made a night light with 32 of them and housed the circuit is a compact cassette case (it is not sealed and leaks air along its hinges). The LEDs are rated for 70mA and I have them at only 54mA but they get so hot I can't touch the plastic case and it has turned cloudy (it did not melt).

A car in summer gets much hotter than in my home.

 

Ok, I understand, I was just trying to help out by keeping things simple but I see you've already tried the simple and it didn't work.
It seems that Bill Marsden and SgtWookie really have there act together when it come to electronics! Hats off to you guys!
I'm a beginner/intermediate with certain things such as designing[SIZE=+0] [/SIZE]the circuits but in the automotive field, I'm an expert. I troubleshoot automotive electrical \ electronic systems knowing what the outputs should be and what is at fault but it is a whole new world when getting this in depth with the components and theories and what really makes them tick. I guess the best way to explain it is that I monitor the behavior but they manipulate the behavior. That is it in a nut shell.
I monitor voltage drops but they make the voltage drops, I check the pulse, they make the pulse. They are like God or something like that.
I might be off base a little here and there but I will at least try to be helpful if I can. It is good if I'm corrected, that's how we learn.