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Here is how to make an LED brake light for your motorcycle. It doesn't have detailed schematics, but there is a nice photo gallery of the build process. There are several advantages to using LED's according to the author:
- Instant-on - There is no filament to heat up, so the light comes on immediately. This should attract others drivers' attention.
- Uniform brightness - By using 80 LEDs, I can fill the taillight evenly with light, thereby making the most of the limited area I've got.
- Higher brightness - I can make the brake light brighter than stock.
- Lower power - At maximum brightness (which I won't use), this light takes 20 Watts -- less than the 35 Watts the normal taillight takes.
Make a LED Motorcycle Tail Light - Link
This is a questionable hack. Usually lights on vehicles are designed to fullfill a certain duty. If somebody comes along the way an just changes them to "higher brightness" lights, it might be counterproductive. Other drivers might just be blinded or surprised. And frankly- have you ever experienced a backlight that was to dim so that it created a dangerous situation? And there is another important issue! Your insurance might not pay if you modify the vehicle. Here in Germany you will lose the permit to operate that cycle, which means no insurance will pay any damages even if they have nothing to do with the mod. And the police will take your licence and charge you a nifty fine. The only advantage of this mod is the fast rise time. That might actually buy some important milliseconds in the event of a crash. But the power consumption is still wasteful. Resistors? And so many of them? Not good! Use a switching regulator in constant current mode.
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I did something similar to a friend's electrically-assisted pedal cycle:
http://www.flickr.com/photos/anachrocomputer/sets/72157594325040749/
The legal issues are not so much of a problem for a vehicle like this! I've also added a high-level LED brake light to my electric bubblecar:
http://www.flickr.com/photos/anachrocomputer/1902440569
In that case, I used a ready-made LED light-bar, which would have been approved for such use.
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@Timbo
The biggest danger on bikes (apart from driving like a testosterone fueled idiot) is being spotted too late, so this would definitely be worth considering for me.
On a motor bike your visibility is poor, this seems to be a good way to get better visibility.
The instant on won't save valuable milliseconds, it will get the attention of other drivers since it is unusual.
However if you would get in legal trouble for improving you bike light, it would be a different story, I'm gonna have to check the laws on that over here.
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@Timbo:
about blinding other drivers he has this to say:
I want to incorporate a light sensor in to the design. This would allow for brighter-than-usual operation during the day (so I can be more visible), but normal operation at night (so I don't blind people). I've also got an idea for a microcontroller to do some extra stuff...
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@Timbo:
You make some very valid points about insurance and the law. Thanks.
I ride motorcycles, and yes I have seen brake lights that were too dim (both cars and bikes)
They make after-market brake lights for this exact reason.
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I don't know why all signals on all vehicles haven't been turned into LED's yet. Does anybody know what advantages that regular lights have over LED ones?
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@ Timbo:
You must not ride, otherwise you would not worry about someone NOT seeing you. On bikes there is very limited space for lights, and usually they are too small. Personally I have turn separate signals and intergraded turn signals + brake light (half of it flashes per direction) just so the 'soccer mom in the SUV who is talking on the cell phone" can hopefully catch the lights out of the corner of her eye and thinking about using the big pedal.
The idea of putting a light sensor in to allow for a brighter output during the day and lower at night is a really good idea.
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A coworker of mine did this to his bike's turn signals, but he had a problem with them not cycling on and off as usual. I think he said that it was b/c the led's weren't drawing enough current, which in turn, didn't actuate the relay. He fixed it by placing a big fat resistor inbetween to increase the load/current.
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A more efficient way to get the leds blinking at a normal rate would be to replace the thermally activated relay with an electronic one. This way, blinking rate won't be affected by current draw, and you won't be heating up a big load resistor.
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@ Captain Obvious: I don't know why all signals on all vehicles haven't been turned into LED's yet. Does anybody know what advantages that regular lights have over LED ones?
well, it's mainly to do with a) they need to be non-replaceable and b) the design cycles are long and c) if you want something to do both ECE and DoT authorisation, it ain't gonna work as we use different colours.
Let's not talk about expense of LEDs, failure rates or extra circuitry (direction indicators). Check out the LED lamps that are available - and authorised - they're not cheap, at least not for a car
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