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Replacing stock tail/stop on VTR250 with LEDs, half-arsed style

Discussion in 'Modifications and Projects' at netrider.net.au started by wokwon, Oct 3, 2011.

  1. Hi all, please see linked PDF on how I did this project. The content is in the next post:

    PDF 1.1MiB - LED-i-fying VTR250 tail lights

  2. The stock tail of a VTR250 is a single 21/5W bulb. This single bulb does the numberplate light, tail and stop all in one. The tail is too dim at night and the stop is not very visible during the day.

    I bought a supposed high-brightness BA-15D LED bulb from ebay. It wasn’t really any brighter than the incandescent bulb but at least it had the fast rise time of LEDs (LEDs come on almost instantly whereas incandescent bulbs tend to fade on and off). Unfortunately it had to be a white bulb so that the numberplate wasn’t lit up red. If I could use a red BA-15D LED bulb it would be much brighter as the narrow spectrum LEDs are much more efficient.

    So in the spirit of making things overcomplicated, I decided to make my own.

    Step 1: Buy a taillight assembly from a wrecker or spare parts dealer.
    You could just modify your existing assembly but I wanted to be able to return the bike to OEM easily when I sell it (would you buy a bike from a guy who kept modifying things?).

    Step 2: Bake tail light assembly in oven at 70 degrees for 10 minutes
    Seriously, this softens the glue that holds it together without damaging everything else. You can then easily prise the two halves apart to get at the yummy filling. Don’t try to explain to your flatmate why there are bike parts in the oven, he won’t understand.

    Step 3: Acquire LEDs
    I got my LEDs from TopBright LEDs on ebay. You can of course get them from anywhere else. Here is what I used:
    (From left to right):

    • Amber 1W 300 candlepower Leds in 40° and 120° 8mm for a future mucking-about-with-blinkers project. These have a forward voltage of 2.2 – 2.4 volts so 6 in series give us a useful range of 13.2 – 14.4 volts.
    • Red 1W 300 candlepower LEDs in 120° 8mm for the stop light. Again 2.2-2.4 volts. At about 14 volts these got quite warm but I figure the stop light is intermittent use only so I’m not worried about it.
    • Warm white 0.1W 11 candlepower LEDs in 120° 5mm for numberplate lights. These have a forward voltage of 3.0 – 3.6 volts so 4 in series gives us 12-14.4 volts. I was a bit worried about the low 12 voltage so I added a normal silicon diode in series that drops a further 0.6 volts.
    • Red 0.1W 21 candlepower LEDs in 120° 5mm for tail and clearance lights. Vf 2.0 – 2.4 volts with a diode in series as they ran a bit hot without it and will be on all the time unlike the stop light.

    All up there was about $50 of LEDs but I had heaps left over for other random projects.

    Step 4: Vero board
    This should actually be the planning stage but I didn’t do any planning. I just got some vero board from Jaycar and started arranging LEDs on the board. My only constraint was that I needed strings of 6 LEDs (4 for the numberplate light) so I started arranging LEDs in pretty patterns after cutting the board to fit in the space of the tail light assembly.
    I did try to ensure that there are at least two strings of each light in parallel as the 6 LEDs are in series so if one LED fails the whole string goes out.
    ^^ Veroboard hacked into shape and the space in which it fits

    I couldn’t find my coping saw so the I had to cut the board with aviation snips, hence the rough edges.

    ^^ Stop lights front and back

    The stop lights are just two strings of 6 LEDs in parallel. In my testing they drew about 280mA each at 14V which is within the 300mA max rating of these particular LEDs.

    ^^ Tail lights added to sides

    The tail lights are 4 strings of 6 LEDs same as the stop lights. I had to file the little rim off the bottom of the LEDs to make them fit together.
    As these LEDs drop off to 25% brightness after 90 degrees off axis, I added two further strips of LEDs pointing at right angles to make up the clearance lights. I’m a bit worried about these as they’re only held in with their wires and might vibrate and fail. I’ll probably pack them with silicone or hot melt glue to provide some more support.

    ^^ Numberplate lights (the LEDs with the little yellow phosphors in the middle)

    I managed to jam in two strips of 4 warm white LEDs for the numberplate lights. Again I’ll need to cover in hot melt glue to support these lights. I also need to adjust every second one about 10 degrees further back as they tend to light up the top of the plate but not the bottom.

    You can also see the diode on the right to drop the voltage for the tail and plate lights.

    The miscellaneous wiring carries the power to each section. The two long red and one long black is the stop, tail and ground wires to go back to the bike.

    The whole insert, solder, jumper stage took about 4 hours including debugging afterwards. Using a current limited power supply is important so that if you get the series/parallel strings wrong (as I did) you don’t toast your LEDs.

    Step 5: Apply lightning and maniacal laugh
    It didn’t work first time but after fixing some mistakes this is what I ended up with:

    ^^ Testing tails, top and side view (top)
    ^^ Testing stop, top and side view (bottom)

    Step 5 – Science!
    OK now before you complain, I know a light meter (measuring lux) is not a good way to compare light output of a lamp. This is because an incandescent lamp radiates in a mostly spherical pattern whereas the LEDs are directional and have lenses in front of each one. However, as a comparison:
    Brightness (with diffuser, measured on axis 100mm above normal position of lamp) @ 14 volts:


    So with this method, we see that the tails are about 60% brighter and the stop lamps are twice as bright.

    Note: I have no idea what the spectral response of my light meter is. I suspect it’s calibrated for daylight so it may read over or under for narrow spectrum red light. It will also read VERY low for the warm white LEDs as they tend to have a blue spike, a red spike and nothing else.

    With the diffuser in place:
    ^^ Stop, Tail and Plate lights

    I was using my phone camera above so the exposure changed between the stop and tail shots. As the tail clusters are on in both pictures there you can see how much brighter the stop cluster is than the tails. It still looks kind of cool after shining through the diffuser.
    The warm white LEDs look yellow in this picture but they’re actually pretty close to daylight coloured.

    Step 6 – Assembly
    I previously mentioned that I didn’t do any planning. This is where it came back to bite me.
    I never considered how to mount the board in the lamp assembly. In hindsight I should have left room for PCB standoffs but in this case I made do with hot melt glue and zippy ties.


    Then the light was glued back together and bolted to the bike. Note: to make the connection, I smashed a BA15d lamp and soldered my wiring into it. You can get empty ones on eBay but like I said before, what planning?

    Step something: Final tests
    For comparison, these shots were all shot at 55mm ISO400 f/5.6 1/125 so the exposure is all the same. Note that these were shot without the engine running so the battery was at about 12.4 volts. Idling I usually get about 12.6 and at 3000RPM plus it goes up to 13.8 – 14.2 which makes everything significantly brighter.

    ^^ Tail (L) and Stop (R) for OEM incandescent (top) and LED (bottom)

    I just put a brick on the foot brake to light up the stop light. As you can see there isn’t much between tail and stop in daylight.

    Sorry, forgot to put the seat back on before the LED shot so there is less contrast. The problem with the LEDs is that they just white out the sensor in my camera in a tiny point so it doesn’t actually look that much brighter than the incandescent lamps.

    While the difference isn’t that much in the pics, real world the LEDs are much more attention grabbing. It’s probably because they are point source lights instead of a big spread. Much like when the cars went from the translucent diffusers to those little reflector thingies that spray hundreds of points.

    I didn’t take any pictures at night but to be honest, I’m a bit worried about the stop light. It’s really really really bright. I’ll have to canvas some opinions on whether it’s painful or not. I reckon it’s still not as bad as those BMW drivers who insist on putting their rear fogs on in clear conditions so we’ll see how it goes.

    Step 8 - Beer
    In conclusion, yes it was totally worth it. The fast rise time of the LEDs is attention catching (I’m one of those paranoid knobs who flash their brake lights when a car comes up behind me at a stop light) and the tiny little stator on the VTR250 doesn’t have to work quite so hard to supply the bike electrics.
    I went for a ride for a few hours to see if it all would fall apart and so far nothing bad happened.