12v brake and tail lights?

I'm trying to build a brake/tail light out of LED's for my motorcycle. How do I make the red brake lights brighter than my red tail lights?
I'm using 3mm 12v (resister pre wired by supplier) and/ or have similar 10mm lights available too.

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-max-3 years ago

The easiest way to do it if you do not mind inefficient use of power is to have a , say 10-100 ohm resistor in series with the (presumably 12V) LED fixture and have that be shorted by a relay or microswitch when the brakes are pressed, so electricity can bypass that resistor.

-max-3 years ago

Only light up half the LEDs for the regular red light, and have the rest come on when the brakes are pressed. If it is already a fixed LED fixture and all the LEDs are on the same circuit, using a switchmode power supply (LED driver) with adjustable current output will be the way to go.

dthing (author) 5 years ago
Update to my questions regarding "brake and tail lights" 6 volt

I found a 1" 9-led disk to use as a base, used 2 white leds along with a piece of used led lead wire to gap the missing light . I soldered in a 1 ohm resistor to the pos side and the brake light was done. Then I soldered a 150 ohm resistor to the pos side with a longer wire and my tail light was done. I know 3 red leds would work equally but I'm using a red lens cover and I thought white would be best. To all those who posted suggestions,Thanks for heading me in the right direction.
dthing (author) 5 years ago
Would it work if I use the brake lights in parallel and the tail lights in series?
Like i said use the existing in line resistors and a set of your own resistors. Play around with the resistor values a bit till you have the LEDs as dim as you want them. The LEDs with your resistors attached will be the normal tail light. Then wire it up so when the break is hit the power goes through the break switch and too the LEDs bypassing the second set of resistors so the LEDs will show at there full brightness.

The attaches picture should help.
The resistors at the bottom (R1 and R2)  represent the inline resistors that came on the LEDs. The top resistors (R3 and R4) are the resistors you will add. Now the switch at the top left (S1) is the switch that powers the tail light or the wires from the tail light side of the connector on your bike. As you can see the power goes through the switch, to R3 and R4, through the LEDs and R1 & R2, and then to ground keeping the LEDs dimmer for the tail light. The second switch (S2) is your break. When you hit the break it allows the power to bypass R3 and R4 thus allowing the LEDs to shine at there full brightness. It really is the most simplistic arraignment for this kind of application.
tail light.jpg
dthing (author)  mpilchfamily5 years ago
Thanks for that. I see. Would I have to use an additional resistor on each led or could I use one resistor for say 6 leds. thanks
If the LEDs do in fact have a resistor on them already and can take 12V, then you would need a second resistor to dim the LEDs further for the tail light.
dthing (author)  mpilchfamily5 years ago
Each led has its own resistor wired in by the manufacturer for 12v. I plan on wiring 6 of them in parallel and am wondering if I can add one extra resistor for all 6 leds to the tail light side. Or do I need 6 extra resistors (one for each led?) thanks again
All you need is one more resistor on each LED for the tail light side.
dthing (author)  mpilchfamily5 years ago
Bummer! that means way more wires than I hoped for. If you would, let me know if I can add resistors in series along the tail light wire instead,that would simplify things. I can't wait for my breadboard, LEDs and resistors to arrive so I can start messing around with my options. mpilchfamily, Thanks for all your replies :{ )>
Why does that mean way more wires. Put everything on the breadboard. Then you will only need the 3/4 wires from the tail light assembly feeding into the breadboard. I picture of the LEDs your using might help. I'll put together a quick little PCB layout for you later today.
dthing (author)  mpilchfamily5 years ago
I think I get it. So the same lights start as tail and then brighten when the brake is applied, right? Current would flow thru both s-1 and s-2 at braking and then only flow thru s-1 when brakes are released?
Yes they get brighter on the breaking.

Current will always take the shortest and easiest path it can take. So as soon as S2 is press (break is applied) current has a shorter and less restricting rout through S2 and will bypass S1 and the resistors there altogether.

On the light connection on your bike you will either have 3 or 4 wires available. If its 3 wires then one is the common ground while the other 2 go to the tail light and break light. If its 4 then one pair is for the break and the other pair is for the tail.

When you wire this all up just be sure that the wire for the breaks is between the second set of resistors and one lead of the LEDs. Otherwise applying the break will not bypass the second set of resistors and allow the LEDs to shine brighter.
iceng dthing5 years ago
It would still require two resistors.. -.-. . -. --.
You can use fewer LEDs when just the tail light is on and have the rest light up when you hit the brake. Alternately you can use your own resistors on the LEDs to they are dimmer and have the breaks bypass that resistor set allowing the LEDS to show full brightness.
+1 on either of the ideas. Just make sure that on the brightest setting you don't overload the leds.
He mentions the LEDs have a resistor pre wired to them from the manufacture so that shouldn't be an issue unless he is using a higher voltage then the rated forward voltage of the LEDs.