aux brake light relay

[mwood7800]

on my r1200rt 05, I read somewhere on this sight that you could add a simple relay to run a aux brake light. I know the light is 3v on run and 12v on brake. I don't care to buy a 100$ adapter if a relay will do the job, has anyone tried one?

[racer7]

Can be done with almost any normal 12V automotive relay because the trigger voltage requirement is in between 3V and 12V. So its off when only tail light is running and on when the brae light comes on.

 

However, the following has been reported to be compatible with the pulse modulated system of the BMW also. Gives you a tail light also and its less expensive in total.

 

http://www.maxxima.com/products/product_detail/10/M42205R%20Surface%20Mount%20Stop/Tail/Turn%20Light/view/.html

[dirtrider]

on my r1200rt 05, I read somewhere on this sight that you could add a simple relay to run a aux brake light. I know the light is 3v on run and 12v on brake. I don't care to buy a 100$ adapter if a relay will do the job, has anyone tried one?

 

Evening mwood7800

 

Not saying it can’t be done but it will be a difficult nut to crack (just) using a mechanical relay.

I tried configuring a micro relay on my first 1200RT and just couldn’t get it to work. For one thing your tail light isn’t a constant or regulated 3 volts it is pulsed (or pulse width modulated) 13 volts (13-0-13-0-13-0, etc). The time on vs the time off gives the tail light it’s decreased intensity. I also measured the tail light voltage at around 6 volts but even that was difficult as my meter response had difficulty with the pulse width vs voltage vs load. With the addition of a capacitor and some resistance I could get the relay to buzz and sometimes trigger but once triggered on it would then tend to stay on and the trigger point was so finicky that just the voltage variation between engine idling and high RPM would render it useless.

 

I did manage to get a Zener diode/transistor controlled circuit to work a little but gave up when I found an LED array that would respond to the pulsed tail/brake voltage just like the incandescent BMW bulbs would.

 

If you read of a relay working then in my estimation it wasn’t just a simple mechanical relay but had a heap of other electronics that went with it.

OR, you read about a relay being used on the early 1200GS as some of those didn’t use a pulse width controlled tail/brake light.

 

 

 

 

[johnlt]

I had a very bright plug and play LED replacement for the OEM tail/stop light that I got from Touratech. It was really slick and only required a large resistor in line to match load. It was programable for solid or various sequences on the stop light. Worked great but died after one year and TT told me that the company went out of business so they refunded my money (not cheap). I had the same kind on my GSA. I sure wish someone would take that design over and manufacture it again. It was the best I'd ever seen by far.;