i'm about to go all LED for my JDM taillights... i've already made myself a nice set of angel eyes, so i know how to solder and work with resistors and such... but i have a question for someone who might know a little more about them... i would really want to have my whole brake light section lit up by a rectangular board with a crap load of LEDs (neatly arranged of course! think G35...), but i don't know how i would rig it so that the LEDs light up at half instensity when just the parking lights are on, and light up at full intensity when i hit the brake. if i dont figure this out, then i might just go with a rectangular 'ring' with LED's always on that aren't hooked up to the brake light, and have all the LEDs inside that 'ring' light up when the brake is pressed.

Would anyone be able to help me? I've wanted to do this for so friggin long, and now that i can get 100 bright *** red LEDs for only $25, i'll be done in no time...

Thanks in advance guys!

 

So you want them to get brighter when you hit the brake. You need to reduce the voltage somehow. you could use a resistor, but it would have to be one hell of a resistor since it will be on all the time when you have the parking lights on.

The other option I can think of is to wire up one of your brake light conversions and hook it up to your battery to see how brght they are. If you get some 3 volt LEDs you should wire them in sets of 4 in series (12 volts divided by 4 is 3 volts)and then wire the groups or 4 together in parrallel. So now you should have your one taillight running at full intensity which would be like brake lights. Wire the other tail the same way.

Now, if you take a wire and hook the 2 tails together in series, you should notice that both tails will be 1/2 of it's full brightness. I think that would work for parking lights. Now add a relay or 2 into that wire so that both tails get 12 volts when you press the brake pedal and each tail should go to full intensity.

 

yeah, that could work, but now matter how many led's i used, i would still need to figure out what kind of relay i need for the half brightness/full brightness to work...i guess thats what i really needed to know... you know those 1157 "dual filament" red LED bulbs that APC makes? i had some of those a long *** time ago, and i noticed that all the LEDs on the base lit up when the parking lights are on, and they all lit up brighter when the brake was hit... do you think there could be some sort of tiny-circuit-board-relay thing inside that base? i'm seriously thinking about buying another of those bulbs and tearing it apart to see whats inside

 

maybe this will help
http://home.howstuffworks.com/dimmer-switch.htm

its about dimmer switches and how it went from using a resistor to cutting electricity off every quarter frequency or so.

 

Well, this is what I was thinking. You hook the 12v positive to tailight 1. Put a wire from tailight 1's negative to tailight 2's positive. Ground tailight 2's negative. This should be 1/2 brightness bacause the 2 tailights are in series.

Cut the wire between tailight 1 and tailight 2.

Put a relay where youjust cut that is normally closed (so parking lights work). When this relay is triggered it should create an open in this wire (parking lights go off) and provides ground to tailight 1's negative (tail light will go to full brighteness). Another relay would also be triggered and provide positive to tailight 2's postive (so it goes to full bright). You may be able to find a relay that will do both of these tasks at the same time so you only have 1 relay.

 

okay i see how that works now... but look at these diagrams i just drew up real quick... i actually just went to pep boys and bought a dual fil. red LED bulb and ripped it apart to see whats inside, and if i'm correct, this is how it is set up:


in this photo, the parking light wire is connected to two resistors (i noticed the resistors had different colored bands, but i don't think this makes a huge difference), resulting in mass resistance when just the parking wire is activated.



in this photo, the brake wire is connected to only one of the resistors, which, I'm pretty darn sure would light up the LEDs more than the parking wire would.

Now if the parking wire was activated while the brake was on, i can only imagine that the LEDs would get only slightly brighter than their 'brake light' intensity, because you're giving more power to the LED's. It would only get slightly brighter, right? Since the most powerful of the currents is already activated?

Even if it was noticeable, how often do you turn your parking lights on while your brake is pressed?

By looking at these pics, do you think this would work? Because I saw no type of relay inside the APC LED bulb i just bought. And I would rather not use bulky relays...

 

The only reason I'm sketchy about whether or not this'll work is because the brake wire is connected to the parking wire, and if the brake wire is activated, won't power be going through the parking wire (since they're connected) thus lighting up everything connected to the parking wire???

 

i think you should take care to note the pattern of the bands being that they denote specific resistace ratings.. it's pretty crucial to limit the power going to the lights in different instances. ie. no brake- parking light on; parking light on- brakes on; or brakes on...you could be right, but i'd play it safe and not end up looking like youre on the brakes all the time.

 

yeah, i know what ya mean. i guess i only said that because both resistors look the same, and the only difference between using one or both, is that it should be cutting about half (or close to half) the resitance, right? so i assumed there wasn't a big difference between the two...

 

The resistors are providing a set ammount of voltage to the LED's. I don't know why they put that one resistor between the LED's and the power wire. My only guess to that is (if your sketch is correct) the 6 LED's are rated at about 1.5 volts. 1.5 X 6 = 9 volts so they threw in a resistor so you don't overdrive them. So what happens when your battery voltage dips to 10 volts? You don't want your LED's to get dim do you? You would want to make your LED circuit total up to 9 or 10 volts. Add a voltage regulator set for your LED circuits rating. That "guarantees" that you will have your LED's driven at their maximum potential and never overloaded. The voltage regulator will see the 12 or 14 volts and dissipate it back down to your set 9 or 10 volts.

You could also use another voltage regulator to set your parking lights to 6 or 7 volts.... or whatever you want. Put a diode in there so you don't get the brake lights feeding back into the parking light circuit.

I don't like resistors, but if that's the way you want to go then have at it! Your circuit should work ok (except for the dimming/brigthening effect dependant on the battery voltage).

 

I dont know if it'd help you but they sell 3 legged 12volt voltage regulators that will ground out voltages higher than 12v. That'd be a good starting point so you will always have a set amount of voltage instead of variable.

 

whoah! whats a diode??? something that prevents current from going a certain way? Hey that could be useful...

Sorry for the crappy diagram... wasn't very accurate... there are actually about 13 leds on the bulb...

 

why not take a multimeter and see how much voltage is given to the bulbs with the parking lights and then get someone to step on the brakes for you then see how much is put out correct me if im wrong but isint it the harness or something already in the stock circuit that does the dimming for you unless LED's cant shine at 2 diff intensites by varying voltage i dont see a problem, just replace your incandescent bulbs with your LED's


BTW a diode is an LED, LED stands for light emmiting diode

 

Ohm's Law:

V=Voltage (V), I=Current (A), R= Resistance (ohms)

V=IxR, I=V/R, R=V/I

hope that helped...LOL!!

 

okay i just learned what a diode is... okay so now i have another question... if I were to use about 40 red LEDs (2 volts each) for each taillight, what kind of diode would i need? cuz now that I think about it,i think there might have been a small diode covered in solder in that one APC LED bulb that I couldn't see...

 

The filiments inside the stock bulbs are different so one shines brighter than the other. Both parking and brake circuits are 12 volt.


Diodes - yes they restrict power from flowing "backward" in a circuit. Yes, an LED is a diode. It will NOT light up if you hook it up backwards.... it will probably fry. Wrong kind of diode.

 

I think you'll need dual band LEDs. Most LEDs light up at a certain voltage, usually 1.5V. The reason LEDs are cool is because they instantly turn on and off, they don't warm up at ll. So I don't think normal LEDs will get a bit dimmer if you give them a lower voltage. My current project is putting two 4" circles of LEDs in each side of the brake light housing. I already bought stupidly bright LEDs that are rated at 7500 mC. They cost my $50 CDN for a hundred though.
To make my park lights dimmer I'm just gonna light up two of the four rings that make up one circle. You could also use dimmer LEDs.

 

well, for anyone who cares, i found a website that sells a product thats turn any LED brake light into a 'double filament' light, so that your LED 3rd brake light, or any other LED light for that matter, can act like a parking light/brake light/turn signal, by lighting up half-intensity for parking lights, and full intensity for brake (or turn) for only $5 per LED light! There's probably an easy way to utilize only one these park/tail/turn converter kits for your whole LED tail setup instead of buying one for each light, but anyway, here's the link.

http://www.watsons-streetworks.com/leds_plus.html
You gotta call to order, but nothing too complicated... It's called an "LED Conversion Kit"

Thanks for everyone who helped me with this! Has anyone else considered turning their tails all LED? I think i might stick red LEDs in the turn signal too (but keep the JDM amber wrap-around)

 

Hey guys guess what an LED is, Light Emitting Diode

 

Optics said that about 5 post up.

 

i knew there were such things as diodes (not the light-emitting kind), i just never knew what they were called.