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490 Posts
Discussion Starter #1
As this is meant to be a tutorial, please feel free to edit everything i wrote so it will be in good english. I'm doing my best, but since my english is self-taught i'm sure i'll do a lot of mistakes

How to add backlight to handlebar switch assy

I liked the idea of having a backlight on the "colored" buttons, but i had two problems:
1) I'm cheap :D Really, i don't want to spend too much money on aesthetic things.
2) usually LED lights become hot, and i did'nt want to take any risk

So i was thinking about how to do it and did'nt have any good idea until i opened a dead LED bulb from my house hoping to find some working LED.

What immediatly hit me was the lack of a transformer: that bulb works by making the 220V AC to (more or less) 240V DC and then appky that (insane) tension to a serie of 12 LEDs. Talk about doing cheap things.
Anyway, the relevant part is that each of that LEDs must be able to handle (240/12=) 20V! No surprise that they burn out.
So, i tested one of them at work, and that was true. They works at full power around 18V. Giving them about 12~14V makes them working very easy, without too much light and without generating any heat. So, that was the solution to both of my problems! :D

The first step is to remove the LEDs from the bulb and attach some wires at them:

With a drill, i've done a 2mm hole in the plastic, to make the wires go from one side to the other.
(2mm was enough for two of my wires, different wires may require a larger diameter)

Then i've filled the button cavity with hot glue, and sunk the LEDs in it.

The wires from the UP must go to the other side thru the hole.

and the all the wires will go out from the bottom of the button "frame":

I've done the same for the "D-M" button: it don't need a hole, but pay attention that the hot glue will not bulde outside the button "top":



490 Posts
Discussion Starter #2 (Edited)

Now: i want them to stay LOW; i don't want them too bright and i don't want the hot.
So i added a 540ohm resistor: with 12V they will be barely lit (all my images are made with 12.6V). With the running bike they will have about 14V, and will be more bright.
Here the resistor soldered to the positive wires:

(yes, that soldering is ugly, i've redone it without taking a picture)

Also, you'll have to sold all the ground wires:

The ground wire (white, in my case) was solded to the horn button ground (the BLACK/WHITE one), and the positive (Brown in my case) to the central point of the LO/HI beam switch (YELLOW/WHITE).
Then it is just a matter of putting everything back in the assy: pay attention that all the wires are out from the handlebar space and that the UP/DOWN button wires will have a bit of "sag" to handle the button movement.
(sorry, no images :( )

A quick test (at 12.6V):
you can (barely) see that the light absorption is less than 1mA. At 14V will be around 4 or 6 mA. Low consumption = low temperature ;)

This is the final result, alone and compared to the dash light (the scooter was just lit on, it was not running, so the backlight of the button i very low):

Hope this will be useful for someone else


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