Topic: electrically gifted people please read this ~

[78whiteorbs]

http://dotheton.com/index.php?topic=10210.0

this is what I am trying to do with my tail light . Any electrically gifted people know what kinda resistor I should get and where exactly you install it in the ciruit?


 You might try looking at led trailor lights. I  have one on my bike and it works good. You will need to modify it to work as a tail/brake light but this is easily done by taking a resister at the right ohms connecting   the running light to the resister and jumping the resister with the wire coming from the brake switch so that when the light is on you get 6-8v and when you hit the brake you get the full 12v. this will cost about $10-15 and about 5min- 1hr depending on how you have to mount it.

this could save mucho dollars for people!

[Industrial Cafe]

something is strange about this thread, is that a quote in there?


you'll need a 12v ballast resistor I think.

[78whiteorbs]

Jep, from the http://dotheton.com/index.php?topic=10210.0

"You might try looking at led trailor lights. I  have one on my bike and it works good. You will need to modify it to work as a tail/brake light but this is easily done by taking a resister at the right ohms connecting   the running light to the resister and jumping the resister with the wire coming from the brake switch so that when the light is on you get 6-8v and when you hit the brake you get the full 12v. this will cost about $10-15 and about 5min- 1hr depending on how you have to mount it."

that was the quote .

[Industrial Cafe]

oh i see now

[78whiteorbs]

Found another example but no specifics:

"You should do a quick addition for dual intensity.

Taillights are on "dim" (parkers?) then go bright for brakes.

Its really easy to do by wiring some resistors inline;
the brake signal bypasses the extra resistors for extra brightness. "

from http://www.drccentral.com/forums/index.php?showtopic=13466

[bmarshall]

I second the trailer light (I did regular bulb, about $12 bucks), I did that on my RD400, go to autozone or any auto parts store (can't think of the name). I got some aluminum L channel and 90 degree brackets and all is good! Some have a black rubber gasket around the edge, some don't.

[78whiteorbs]

bmarshall , how did you make it work as a running light and tail light specifically?
I am basically mildly retarded with electricity so use laymen s terms please. You got your tail light working as a running light and a brake light right? If it just a cheap regular light then it has to be modified. I am interested in the details of this mod,eg what resistors and wear to wire them  blah blah blah

[Industrial Cafe]

yeesh-

[Industrial Cafe]

what's wrong with something like this, but in red?

http://cgi.ebay.com/ebaymotors/2x-1157-AMBER-36-LED-TURN-SIGNAL-BRAKE-CAR-LIGHTS-BULBS_W0QQcmdZViewItemQQhashZitem27ad034c34QQitemZ170406399028QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

[Gorms]

I could be wrong, but I dont think LEDs have variable brightness based on the voltage you give them like incadescent bulbs can (to a degree).  They require a specific (lower) voltage where anything less wont turn them on and any more and you will ruin them.  To make them work in a 12v system, you must use V=IR and P=IV to find the required resustance you must add and at what power rating.  Incandescent bulbs come in dual filament bulbs to give you a running and a brighter brake light.  For LEDs I would imagine only a fraction of them light for running lights and they all light for the brake light.

[Industrial Cafe]

my tail light uses a resistor on the LED bar for dual intensity.

in my personal experience LEDs will light up from 1 volt to the maximum recommended voltage just like a light bulb.

[78whiteorbs]

hmmm, that would coincide and sounds sensible about the only one brightness from an led.  Well nope that can't be right . Look at IC's posted brake/running lights

on my thread here http://forums.sohc4.net/index.php?topic=60862.50

IC you got two different brightnesses from the same LED's right?

[vanillagorilla]

I am reasonably trained and experience in electrical matters.  But, I can't figure out what you want to do or with what.

Specify what bulbs/units you wish to use and for what function.

 I do understand you want to change something regarding the tail light.  Something about changing from an effective large lamp that signals other drivers where and what your bike is doing, to something other drivers will hardly notice making it even more likely they will run into you.  Later, you'll probably complain of other drivers not seeing you despite how loud your bike is.
Did I get this right?

Still, if you want to increase the risk of riding, I'll help you with the electrical, provided you have something specific in mind.

Harsh...

[vanillagorilla]

Did you read what he had posted earlier? I am by no means a smart man, but I understood what he was trying to acheive. Dont know the answer, but I understand. Seems like you felt like lashing out at a young whipper snapper to me. While he is trying to save a buck and give the rest of us a good tip, too... Sorry if I offend anyone, but I thought that was a little unnecessary.

[Spanner 1]

+1 with Ind.Cafe....LEDs are either on or off..can't be dimmed....what you want to achieve would ( for example ) have maybe 12 LEDs, 6 connected to the tail-light wire and 6 connected to the brake light wire..i.e., tail=6 LEDs, brake=12 LEDs......'cos brake comes on in addition to tail-light....easily done.
Whoops that is +1 with Gorms..... sorry.

[Industrial Cafe]

IC you got two different brightnesses from the same LED's right?

yeah, the kit comes with an inline resistor and bypass, wrapped in heat shrink.

[Industrial Cafe]

+1 with Ind.Cafe....LEDs are either on or off..can't be dimmed....what you want to achieve would ( for example ) have maybe 12 LEDs, 6 connected to the tail-light wire and 6 connected to the brake light wire..i.e., tail=6 LEDs, brake=12 LEDs......'cos brake comes on in addition to tail-light....easily done.
Whoops that is +1 with Gorms..... sorry.

they can be dimmed by supplying less voltage. think about your 2 battery LED flashlight, it gets dimmer and dimmer as the batteries die. it doesn't just shut off when the power goes lower than 3 volts.

[333]

Most trailer LEDs I've seen are already dual intensity, regardless of how it's done.  Unless it's a marker light, in which case, it'll never be bright enough for a brake light.

[Gorms]

OK so an LED may have som dimming capabilities but its over the span of about .5 volts from off to 100% and its not linear.  Its exponential and the useful brightness occurs over a very small upper voltage range which would be hard to regulate and its not really a useful characteristic of LED's as far as I can tell.  You could have parallel sets of up to 6 red (2.2v) LEDs in series which would give you the best efficiency from your 12v source and would applify the .5v dimmer range of the LEDs into about 3v.  But the variability between 50% brightness and 100% brightness of one LED may only be a few milivolts because of the non-linear function.  This would be extremely hard to regulate so I dont understand how it can be done.  Thats not to say it can't, just that I don't see how.  If its done on one of the systems described above I am curious how.


The easier solution is to have half hooked up to the running light circuit, and the other half wired to the brake light switch.  Scatter them evenly and with a lens over them blending their point light sources, you have a light that appears to be one light source with two brightnesses.  This is the most common.

[Industrial Cafe]

Most trailer LEDs I've seen are already dual intensity, regardless of how it's done.  Unless it's a marker light, in which case, it'll never be bright enough for a brake light.

+1

[Industrial Cafe]

OK so an LED may have som dimming capabilities but its over the span of about .5 volts from off to 100% and its not linear.  Its exponential and the useful brightness occurs over a very small upper voltage range which would be hard to regulate and its not really a useful characteristic of LED's as far as I can tell.  You could have parallel sets of up to 6 red (2.2v) LEDs in series which would give you the best efficiency from your 12v source and would applify the .5v dimmer range of the LEDs into about 3v.  But the variability between 50% brightness and 100% brightness of one LED may only be a few milivolts because of the non-linear function.  This would be extremely hard to regulate so I dont understand how it can be done.  Thats not to say it can't, just that I don't see how.  If its done on one of the systems described above I am curious how.


The easier solution is to have half hooked up to the running light circuit, and the other half wired to the brake light switch.  Scatter them evenly and with a lens over them blending their point light sources, you have a light that appears to be one light source with two brightnesses.  This is the most common.

the led decreases in brightness when you decrease the amperage. that may be what the doodad in my tail light does.
my seat is being upholstered or I'd show you some pics or a video of the wiring and what it does when i do the thing toi  owhf;oaeiuvh;aeworu ;gekfjsdvh ;aekrj gh;eoisdfh ;aewjrl nh;sdlkjvh q;eworu has;ddfffffffffff BARF!!! I'm going to bed.

[bucky katt]

i have an led marker/turn signal light from a tractor trailer shop. 16.95 and the red lens to fit it another 2.95 about 3x as bright as the original tail/brake light

[Steve F]

To achieve the "dual brightness", led lights use a kind of chopper circuit that makes the eye perceive the light as dim/bright.  They give the led's a square wave input that is perhaps 50% duty cycle for a "dim" and full on for "bright".  The duty cycle determines the "brightness" that the eye sees.  That's why (I don't know if anyone else has noticed this) you see some of the newer cars that have led tail lights, and when you quickly glance away from the light, you see multiple images of the tail light. like a very fast flashing strobe.
In the pic below, I used an LED truck tail light that has such a circuit built in to give you the strobing effect, and goes full on when you hit the brake.

[Queeg]

heres what i did its off an old crapnow i forgot .... um 84  v four bike and not the sabre but ..... crap heres a link

http://www.23b.org/gallery/v/23b_members/lthe-life-and-times-of-a-fish/album322/honda/IMG_7505.JPG.html

[78whiteorbs]

Wow , lots of good info. After reading I am thinking the best route my to be as Gorms suggested and dremel in 4 new led locations and put them on the brake ciruit . Would there  be any additional resistors needed I just would be wiring 4 new leds to the brake light from the brake light wire. This is good stuff .

[Raul CB750K1]

From what I understand, the LED unit is a high intensity one. Negative goes to ground, and positive goes to brake switch cable. You actuate the brake, the LED lits.

If you want to use the same LED unit to work as a regular taillight, you are right. You will need to connect a resistor between the taillight wire (+12V) and the LED (+), that by now should be already connected to the brake switch cable. In regular conditions, +12V will feed the LED unit through the resistor, therefore the power will be reduced. When you actuate the brake, +12V will be fed directly to the LED unit, glowing at maximum power. Then the resistor would be connected between 2 positives, being that absolutely harmless.


I have a friend with an old bike, 6V electrics. The headlamp bulb is expensive and difficult to find. Over here it is mandatory to ride with the low beam at all times, and it is bad for the bulb because it reduces its life. What my friend has done is to connect two big diodes in series with the bulb, but only in "parking" position. He rides at daytime in "parking", the low beam is energized throug the diodes, where 1.2V are robbed from the bulb, decreasing a little its power but increasing its life. At nightime he needs all the light he can afford, so he switches to "low beam" where the +12V is fed directly to the bulb. It is more or less the same than with the taillight, but using diodes instead of resistors.

[Gorms]

To achieve the "dual brightness", led lights use a kind of chopper circuit that makes the eye perceive the light as dim/bright.  They give the led's a square wave input that is perhaps 50% duty cycle for a "dim" and full on for "bright".  The duty cycle determines the "brightness" that the eye sees.  That's why (I don't know if anyone else has noticed this) you see some of the newer cars that have led tail lights, and when you quickly glance away from the light, you see multiple images of the tail light. like a very fast flashing strobe.
In the pic below, I used an LED truck tail light that has such a circuit built in to give you the strobing effect, and goes full on when you hit the brake.

Thanks for jogging my brain Steve.  I forgot about the use of duty cycle.

[Industrial Cafe]

yeah me too.
you said "doodie" cycle.

[cycleman]

In a normal tailight set up on these bikes they have a two filament bulb, one for the tail/running light & the other for the brake light.  Some older hard bags like the Wixom had two separtate bulbs one for each of the above that you could wire into the circuit to improve visibility.

From what I've seen/understand of the LED tailights, some have the provision for two different circuits, including a licence plate light.  They basically start off with about 20 or so LED's and then divide them up so that ie: 4 are for licence, 6 for running & 10 for brake.   There are three wires, one for ground, one for running/taillight, one for brake. I'm pretty sure you don't have to do any special wiring with these, but you do if you are trying to use LED's as signal lights.

I'm thinking of doing something similar and have been doing some searching on ebay, etc. & there are some fairly inexpensive setups out there.  Just haven't figured which way to go.

[78whiteorbs]

Raul CB750K1 -  I tried this and maybe I am using the wrong reisitor or something but it isn't reducing it at all the light is the same brightness. I think I am gonn a just wire four more LEDS to the brake light and install them for when the brakes are pressed i will get 10 LEDS glowing instead of six for the running lights. I am assuming I can just run the leds in a series between the neg and positive of the brake wire circuit. 4 LEDS are cheap at radio shak , I will post pictures as to how this turns out . This is the most I have had to use my head in this project so far....bah!  The bike I have has permanantly on running lights/head light so I want to install an on off switch for incase I want them off. This will be interesting and I hope it might help someone save some dough on things that can't be modified or DIY .

[bmarshall]

Mine is a simple 12v bulb w/ 3 wires; running light and brake light, works fine for me.

[Laminar]

Standard 4" LED trailer light with built-in circuit for taillight and brake light. I wired it straight up to the stock tail light wires.

[skamagedon]

67 ohm resistor for every 5 leds for 12 v hooked upon the ground side. leds are generaly 2.2v forward voltage @ 20 mah

[phil71]

not touching this thread with a 10 foot pole. So much wrong info I don't know where to begin.
  I will say only this: DO NOT take advice about what resistor to use by anyone who spells it "resister".

[Bodi]

An LED produces light proportional to the current through it. The voltage across the LED is relatively constant regardless of current.
Again, the light output is proportional to the current: more current equals more light. An LED is completely "dimmable" from zero light to maximum light. The maximum continuous light output is at the rated current for the particular LED. The maximum current is based on thermal properties of the LED, it produces heat when passing current and will overheat and fail if operated continuously above the rated current.
There's a trick, though. If you pulse the LED at a higher current and have the duty cycle of the pulses arranged so the total average power is below the rated power, it looks brighter but doesn't burn out. This can also make a LED look as bright as at rated DC current with less actual power.
Anyway, most trailer lamps have 3 terminals - ground, tail, stop. The current limiting resistors for 12V automotive power are inside, one set for dim "tail" light and one for bright "stop" light.
I don't think there are any trailer tail lamps at your local auto parts store that are pulse driven. The electronics required is much more expensive than a few resistors.

[Gaither]

FWIW, I bought 2 small LED lights (red) with chrome bases. They are about 2 1/2" long and 3/8" wide. I don't know how/why it works but they "burn" very visibly normally for running  lights and also very brightly for brake lights. Both modes use the same LED "bulbs" and appear to have 5 LED "bulbs" in each (enclosed) light.