Resistor for BRAKE lights Question

[EasyRider]

Do you have a Hex EzCan ?

I have and used one of the spare plugs to give me extra brake lights.

I know the EzCan are not cheap, But it will give you the opportunity to add more electronics to the bike without upsetting the Can-Bus.

If i'm off base here, then i'm sorry i can't be of more help.

Brakes ON.jpg (160.28 KiB) Viewed 1938 times

[David.]

Resistors work by converting electrical energy into heat.

A filament bulb is a resistance to the flow of current which creates heat and glows to produce light. When changing to an LED, the equivalent resistance needs to be the same to keep the Canbus system happy. Hence the reason to fit an additional resistor in parallel with the LED.

[Strat Tuner]

I agree. They may be working too hard, but if I understand, using 50w instead of 10w will generate MORE heat.

I've ordered metal 50w, so I may try that next.

I got this far just trying different things, so I guess more experimentation will carry the day.

I don't understand the difference between watts and volts.

Seems to me a resistor that resists more than a 12 volt system puts out would cause the brake light to go completely dark since the resistor resists ALL the output??????

[Strat Tuner]

StratTuner, you can not be that stupid.

Yes, oh yes, I can.

[Strat Tuner]

Resistors work by converting electrical energy into heat.

A filament bulb is a resistance to the flow of current which creates heat and glows to produce light. When changing to an LED, the equivalent resistance needs to be the same to keep the Canbus system happy. Hence the reason to fit an additional resistor in parallel with the LED.

Yes. You have to add a resistor when you change from filament to LED. Got that.

OK now.... so,,,,, what resistor is that exactly.....

Seems to be the question here. :-)

[Strat Tuner]

Do you have a Hex EzCan ?

I have and used one of the spare plugs to give me extra brake lights.

Uh.....what is Hex EzCan ??????

I'll go search that on amazon.

[Strat Tuner]

I found "Hex EzCan" on Ted Porter's BMW site.

NB: I bought my replacement shaft drive from this site and would highly recommend them to ANYONE!

Reading the copy for it, I can see why you recommended it! It seems to be exactly what's needed here. Well done, and Thank You!

I knew someone else had already figured out how to solve this, and indeed someone has!!! So that's that!

At $229, I won't be buying one any time soon, but that's another problem to solve....

[David.]

Watts are a measurement of power, voltage is potential difference.

A resistor restricts current flow which is why they heat up.

[Strat Tuner]

At this point, I'ma considering running a new circuit (a wire) up to the hand brake lever.

Don't laugh. If I did that, I wouldn't have the CanBus/Resistor problem!

Nor would I have the problem of the brake circuit being partially ON all the time. I consider that bad design and hope that newer BMW models abandoned that. The running light should be on a different circuit than the brake light. Brake light flashers depend on those two NOT being a shared circuit.

As for CanBus??? Well, I'd like to give the first annual "MAX GRIEF" award to the engineer who designed it.
Well done, sir!

I am guessing this is dreaming well beyond my ability, since I don't know what sort of ON/OFF switch would work best in the small confines of the hand brake housing! I can't just piggy back off the existing wires since that re-introduces the CanBus problem.

.... Sigh......

[David.]

The diagram came from an article about fitting an LED to a BMW F800, they used a metal 50 watt, 6 ohm resistor secured to the frame to dissipate the heat.

[Strat Tuner]

Watts are a measurement of power, voltage is potential difference.

I'ma sure that is 100% infallibly correct.

I struggle with how that would be useful in this situation.

How about this: If I buy an LED that has a "wattage" number associated with it, how many watts does the LED have to BE to equal what the filament was? If I could find an LED like that, I wouldn't need the resistor????

I will go and look to see if LED bulbs are rated with a "wattage" use number. That seems like a place to start.

It seems like LED bulbs should exist that have the resistor built in so that the LED would then "resist", consume electricity, identically to the filament bulb. CanBus would not then know we had changed anything.

I'm guessing this would generate more HEAT than even the aluminum housing LEDs use to dissipate heat could handle!

[Strat Tuner]

The diagram came from an article about fitting an LED to a BMW F800, they used a metal 50 watt, 6 ohm resistor secured to the frame to dissipate the heat.

A HA! Actionable information!!

I will buy the 50W, 6ohm units and try to find a place to mount to the steel frame...preferably in the air stream.
The 10W ceramics I have seem to be overwhelmed.

[David.]

The filament tail/brake light bulb is 21W.

Some Can-bus friendly LED bulbs have a resistor built in to replicate that of the filament bulb. If not, then an additional resistor is required.

[Strat Tuner]

The filament tail/brake light bulb is 21W.

Some Can-bus friendly LED bulbs have a resistor built in to replicate that of the filament bulb. If not, then an additional resistor is required.

I have tried many canbus friendly.
None worked.
I'll Google led with built in resistor

[David.]

If the current set up works, how about just replacing the plastic resistors with metal ones of the same value.