Hi All,
I replaced my tail light with a LED.
Nice and bright so that's good,
problem is the "tell tale" is on permanently , so I guess I need to put a ballast resistor in.

Any ideas what value I need ?

Ta

DeRodster wrote:Hi All,
I replaced my tail light with a LED.
Nice and bright so that's good,
problem is the "tell tale" is on permanently , so I guess I need to put a ballast resistor in.

Any ideas what value I need ?

Ta

Putting a resistor in parallel with the bulb to override the monitoring circuit negates the amperage saving LED's give, basically, why have LED's if you are going to use the same amps. 

6-7 ohms, 20 watt resistor should do it though.

A couple threads on disabling the bulb monitoring circuity:

https://www.k100-forum.com/t9923-internal-circuit-modification-for-bulb-failure-relay

http://www.advrider.com/forums/showthread.php?t=339980

http://www.bmwmotorcycletech.info/K-hints.htm

Some parts if you do want to put a resistor in:

https://www.superbrightleds.com/cat/flashers-load-resistors/page/2/

T3CHNO1D

Thanks for that,
Indeed you are quite right if I wanted to reduce my amperage,
but the issue is "safety" and "being seen".
and my buddy tells me my rear light is quite dim,
So I'm not concerned with saving power, but rather getting more light out.

All the best
Rod

I recently had the tail light assembly off my K1100 to do a glue repair on a couple of little cracks in the lens and took the opportunity of thoroughly washing out the inside, it took a fair number of rinses and trying to reach as far inside with a toothbrush as I could, and at the same time I checked the wattage of the bulb. I found that it was a 5 watt bulb instead of the specified 10 watt. Here in Oz 5 watt is the most common for vehicle tail lights so I found it difficult to find a 10 watt bulb at the local auto suppliers - eventually bought some from eBay.

First trip out after the clean and bulb replacement one of my fellow travellers remarked on how much better my tail light was than his (also a K1100), so I can only assume these basic measures have made the difference.

Cheers

Gaz

I did likewise and yes it makes a very big difference. Its worth doing once a year because the bulb itself gets coated in time and visibility drops significantly.

Likewise. Getting a 10w bulb in there is the trick but cleaning the lens out made a big difference

just changing the bulb makes a huge difference ...have now changed mine 4 times since I have owned gerty (4 years )

often found the internals of the globe thoroughly carboned up and reflecting more light in than out ... grin

heres a heads up  with what "avenger gt" did with his tail lights
yes more light out ....and a bigger target area I guess

https://www.k100-forum.com/t1833p250-85-rt-resto-my-attempt-hey-im-not-into-making-a-show-bike#32757

worth thinking about perhaps ?

Hi Rod - I have to echo what the boys said about cleeaning and bulb replaceement. Twice in 5 years I've replaced bulbs as they were becoming less effective but not triggering the warning light. When I had the lens apart I also made a couple of LED stips to fill the voids behind the Red cover with LEDS for extra "bang for your buck" on braking. Very effective.

All very interesting.
I will revert to the 5w (new), but in addition I am going to add a couple of LED's to the side compartments.

Is it the braking you have the led strips for Will ?
I don't think my brake light is a problem @ 21w
but having fitted the red LED in place of the 5w tail it sure is a lot brighter, only problem is the "tell tale" stays on :-( 

What fun
Rod

um rod
not sure if you know ...but the taillamp should be 10 watts ...not 5 watts ...could make a significant difference to what might be assumed as standard
good luck on the experiment ...were all watching to see what happens

Yeah I've heard about it being 10w Charlie99 but it's not a wattage I've come across this neck of the woods
Also the 5w is already causing heat discolouration on the white plastic surround, and presumably effecting the light output.
In any case I have replaced with new 5w and and am in the process of drilling and fitting new holders in the side compartments for the led's.
Possibly as someone mentioned earlier the fitted bulb could be more than a few years old and have lost some of it's lumen's.

As an aside I did a check on the current draw for both the 5w and it's LED equivalent.
5w draws 370 mA
LED draws  40mA
I was going to wire up a wirewound potentiometer across the connectors with the LED in circuit and see at what point it would light up or extinguish. I could then check the resistance and fit an equivalent ballast resistor.
I might yet, but first I will get the current wiring install done

adios
Rod

Rod

Next time you are passing Halfords, they keep them but you have to hunt them out. Had to replace mine last Friday, I do keep spares.

Hope to see you soon too.

Olaf.

by applying a variable resistor in circuit (series ) all you will do is dim the led ( current limiting also implies some voltage drop will occur )

if you were going to put the wirewound potentiometer in parallel it would then draw current itself without affecting voltage drop to the circuit too much
but be carefull how you go as it nears the low end it will sart drawing current at an exponential rate (1squared x r ) just make sure that the pot is rated for at least 3 watts ...on the low wattage side of affecting the bmu operation t make it stop illuminating ...many higher wattage pots become increasingly more expensive than just a few pounds - dollars to buy ..I would try a 47- 50 ohm pot - 3watt rated .


if the led already has some form of current liming going on inside the lamp itself ...if its a multi cell type led than possibly has a current limiting circuit onboard  if its a single element (led ) probably just a resistor to limit the current to near 20 milliamps ....did I see you say 17 ?

keep in mind that you can run about 4 leds in series max (all drawing the same current ie 17 ma )  ...for 4 times the light output ...the dropping resistor changes in value to achieve this ,,,because inherently each led drops some voltage ...most red leds ..somewhere around 2.1 volts each if you use standard "out of the shop" leds with pigtails   ...if you are using 12 volt leds each led has the right resistor on board to drop 12volts only for the current it needs ...so maybe 2 might work ...with no external resistor ( they might be a little dimmer in this situation ) as the current will be restricted by the onboard resistors ..so possibly draw 17ma /2  - 8.5 ma   but actually a little les as the voltage drop principle also changes  
the led strips that are very common often have a tiny current limit chip onboard or again they are in parallel with the right chip type resistor ...or in groups of 3 with the same principal I was trying to explain earlier with just 1 resistor to current limit 4 leds  .

im sure you knew this ...just consolidating the concept for others as well .

good luck rod

Thanks Charlie99, all noted and stored for a rainy day
in the meantime i got to this point looking at the discolouration from the 5w bulb



and then I moved on to this



a slightly different bulb holder than in the previous pic, for the simple reason it fitted the drilled hold quite snug
so then



and some more wiring



and ended up with this



compared to the original



Now I just need a buddy to give me some feedback.

Hmm I wonder if the brake light will be as effective......time will tell

R

DeRodster:

I have been leery of changing to LED Stop Light Bulbs because I have read tests/reviews showing that they invariably did not put out as much light as the incandescent bulbs do.

What brad/model bulb did yo replace yours with?

I would definitely like to be brighter have it react faster and last longer!

Thanks,

Brad

Hi Brad,
Just to be clear I only added a couple of LED running lights.
I left the brake light as it was, 21W is fine and my buddies had no problem seeing it.
The problem was the 5w running light is very faint in daylight so i added the two LEd's ,
one either side in the blank compartments
They are W5W style and the holders I picked up at my local car accessory shop

Good luck with it

Rod