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LED Hella turn signals and electronic flasher

 

 This is not the definitive "how to" in building LED bulb and electronic flasher, It's just something that I thought could easily be done. All of the information is out there on the web, more than one could ever want to know about working with these components. I built this electronic flasher and LED bulb more than a year ago and didn't keep any records of what I had done. So my apologize if it all seems to very fragmented. As I said I'm no electronics guru, if I can do it anyone can. If you need any other information or can make suggestions I'm happy for you to contact me.

 

If you want to see this flasher flash, this is a short WMV media file of the flasher and bar end signal working. I'm standing about 6mts away from the flasher, it's dark outside and the garage light is on. It's a link to the German site Einzylinder zentrum which is also a great site for other BMW 250 information.

"""""Flasher working""""""

The file is 270Kb and you will need windows media player to play it. Sorry about the film quality it was taken on my digital stills camera.

 

I always liked the look of the Hella bar end turn signals also called ox eyes. So I wanted to fit them onto my bike. The only problem for me being that each of the standard incandescent soffit bulbs draws 18 watts…and that’s way too much for my liking.

I wanted to get an effective bright flash but keep the power consumption right down. The only solution would be to build LED soffit bulbs and an electronic flasher.

There are available LED soffit bulbs and electronic flashers, however the bulbs are 12 volts and the electronic flasher too expensive; we can build our own very cheaply.

For these lights I chose the Super Flux LED it's an automotive Led and is available in a variety of colors. They have a high luminosity and a wide viewing angle 70deg, which is something we need with indicator lights. Sustained forward current 30mA @ 3.6V. There is available an amber LED which closely matches the color of the Hella lens. This is good because rather than using a white led and the lens filtering out the colors. It's brighter and more effective if we use the correct color flash led.

Since we need the light to be visible from both sides of the turn signal we need two of our LED's facing in opposite directions. That actually works in favor since the voltage of the two LED's required gives us the luxury of not having to use a dropping resistor in the circuit. If the two LED's are soldered in series we match the 6 volts of our system. In reality there is a slight voltage drop through the flasher so we are driving the LED's at a very safe load.

Flasher unit

The flasher unit is not that difficult to make, all that is required is a 555 timer IC a few resistors and a capacitor.

We really only need to determine the frequency of our flash and that is controlled by the value of our resistors and capacitors.

Rather than me try to explain the workings of the 555 chip there is an absolute ton of information on the web about them, including a lot of fun projects that can be made using the same timer chip.

For the flasher we need an astable timer circuit, do a google search and you will get a hundred hits on how to build the circuit, It is essentially the second most basic circuit that one can build with these timers, so anyone who can solder the end of to wires together should be able to do it.

Probably the most time consuming part of building the timer is determining the values of resistor and capacitor that you will need for the project. It's not difficult; it just takes a little time to get a frequency of flash that you are happy with.

I will direct you to this site which is a big help in making those determinations. One simply plugs in the values of resistor and capacitance and watches the frequency of flash change.

http://delabs.topcities.com/cirdir/tutors/gates/doc00019.html

I would also recommend that you set every thing up on a breadboard before you actually build the circuit just to make sure everything is working correctly. It's a lot of fun

Thanks to Bart Wessel for helping me out on this stuff.

 

This is basically all the electronic components you will need to build the flasher.

AS with the other LED's we need to break the soffit bulb and retain the two end caps. They are simply there to fit into the original position and provide the ground and positive path for our LED's.

After soldering the two LED's together, remember + to + and - to -, I used a simple stick of plastic to support the LED's, anything can be used as long as it is quite rigid and won't flex under the pressure of the bulb holder. Simply thread it through the legs of the LED's and put a dob of epoxy glue to hold them.

 After fitting the + and- leads trim the plastic to the approximate length of the original bulb.

Pot the end of the plastic rod into the end cap, allow for that side to set it shouldn't take very long and then turn it over and pot the other end

 After allowing for the resin to set for a day or so then it's a simple matter of soldering the two wires to the end caps.

Our bulb is finished! We are careful to remember the positive and the negative side of the bulb, not like the original bulb these led lights are polar.

 No special PCB is required since the whole board will be potted into a suitable container with some two-part epoxy resin. We use a piece of project board so that the components can be soldered into position and some mono filament wire to make up the connections

 I have soldered some connectors onto the board and an earth wire. These will be left standing out after potting in the container.

 Any kind of container can be used; an empty 35mm-film case is a good one.

 Whatever containers you use trim the top so that the connectors are protruding. You can also do a final check and see if the circuit is working, before potting.

 Half fill the container with the epoxy resin and place the circuit in. Then carefully fill the container with enough resin to reach the top.

Since it's quite a mass of epoxy it will take some time before it cures fully. And we have finished!

 This is the led bulb in our Hella bar end holder.

 This is the Hella bar end signal connected. Obviously you cannot see it flashing, but the light is bright and very easily noticeable from a long distance.