Flashing Circuit for my home made 5W luxeon bike light

[joedm]

hi there,
I built myself a 5W luxeon bikelight about 6 months ago using a cheap $3 headlight, a buckpuck, heatsink from Jaycar and 12 AA nimh batteries.

My light has been awesome so far however on the bike tracks which are pretty well lit I have found that my small standard led light is better due to it's flashing capabilities to get the attention of on coming riders.

Now i was thinking if i could add a flashing capability to my 5w light, this would really make it useful and also extend the runtime.

Only problem is I do not have much of an understanding of electronics. I can solder and follow instructions quite easily however understanding and coming up with my own circuit design is something out of my depth.

I was wondering that there should have been others out there who would want to implement a flashing function into their homemade lights and if so would you be willing to share your circuit design?

Here is the layout of what my current light wiring is like:

Anyway, if you know of a simple modification or circuit that I can add to my light, it would be much appreciated. Thank you.
Joedm

 

[joedm]

ok, no responses as yet so I have done some of my own research .

And I found a circuit from www.redcircuits.com.

Here is the schematic:

Here's the link to the page (with notes and instructions).

The web page states

Ideal to operate 3 to 24V DC existing on-circuit lamps, LED operation is also possible

Also

Simply insert the circuit between existing lamp and negative supply

and

this device can drive lamps up to 10W

And finally

Although rather oversized, this circuit can also drive any LED, providing a suitable resistor is fitted in series with the light emitting device.

So I guess this is what I am looking for, however not being an EE I am not sure. Since I am already using a buckpuck to convert the supply voltage to the required voltage for my 5W Luxeon, then do I need to worry about this resistor at all? I'm going to assume no.

I think I understand what I need to do but before I go killing my perfectly working light, is there someone out there who can verify what I'm doing?

Thanks.

 

[w0mbatinoz]

This is the best circuit I have seen for a flashing Luxeon. Was going to make one for my RC plane. http://www.rcgroups.com/forums/showthread.php?t=486003 Page 2 gives most of the details.

There is also a nice kit at Oatleys Electronics...... but only for a 1 Watt unit. :thumbsdow

Your circuit looks like a simple flip-flop that will power the buck-boost driver. Should work OK I would think without the resistor, as that is the current limiter which the BB unit takes care of.

Cheers

--w0mbat

 

[macforsale]

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[georges80]

The new version of firmware that comes with bFlex has a bike mode, and one of those can be set to flashing. It can be configured to drive 350, 500, 750 or 1000mA to the LED(s). More info can be found on my website in my sig.

Of course since it is a complete electronics unit, you won't learn much versus building your own control circuit...

cheers,
george.

 

[macforsale]

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[Tritium]

Simple fix is a reed switch between battery and driver. Mount the reed switch near a wheel and a small magnet on the wheel to trigger the switch once per revolution or multiple magnets for whatever flash pattern you want. Use a normally closed reed switch if you want short dark pulses. Use a normally open if you want short light pulses.


Thurmond

 

[macforsale]

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[joedm]

Thanks w0mbat for your reply..

I will pursue with the original flash circuit I found...
Seems a bit less complicated than the one you mention..
however I may end up trying both just to see which what the differences are.

george, yes I am aware of the UIB interface for the nFlex/bFlex drivers. However I have this little voice telling me to give it a go...

If i was to build myself a new bike light (more than likely in the near future) then I will have your driver on the top of my list. The buckpuck is fine however costs a lot without a UI.

oh well... I'm gonna go look for an "Electronics for Dummys" book.

 

[joedm]

macforsale, yes now come to think of it, I think the buck puck also has a control pin. I'll investigate hooking up the flash circuit via that.

Thanks for the reply.

I don't understand a lot of EE jargon/terms so sometimes I have to read the posts a few times before it gets in my head :laughing:

 

[chris_m]

If your buckpuck has a control pin, it should also have a 5V output, so you can simply plug in a PIC or an AVR and have fancy flashing patterns

 

[joedm]

unfortunately I have just checked and my buckpuck is the "N" version which has no dimming via control pin... so looks like thats out of the picture.

Another thought I had was using an existing flashing light circuit and using something like a relay to switch my light circuit?

 

[AndyTiedye]

Adding to Bike Light Threads Index

 

[joedm]

ok, an update... I have just got my circuit from post #2 in this thread working... I have it on a pcb which is rather too big for it... currently using 3 AA's direct drive with one of the chinese leds from an Elly.

Anyhooo... I have it on a runtime test going now to see just how long it goes for..

here's some pics

I tried to capture some video but I guess the framerate on my mobile is too slow to show anything other than a steady light.

Ok, so now I'm past step one. Just gonna wait for my 1W Red Led with 45 degree optic to arrive.

Now what do I do about a housing?

 

[chesterqw]

you will really want to add a heatsink to that luxeon.

even flashing it WILL make it hot

and hot is bad for LEDs!!!

 

[joedm]

It's one of the chinese leds from an Elly that I modded.

In any case it doesn't even get warm at all. I tried to measure the current pulled by the led but I get something like ~100 mA unless I'm not measuring it correctly. The voltage across the led is around 2.6V so it is really underdriving the led (not that I know the rating for this led anyway, just assuming something similar to a luxeon or prolight).

So far it's been running for 12 hrs straight and doesn't look like it's going to stop anytime soon.

3x1.2v = 3.6v therefore dropping around 1V in the circuit. not sure if this is linear.. haven't had time to the algebra but will when i get home from work.

Anyway, easy way to test is to add another 1.2v, up to 4.8v and measure to see how much is dropped by the circuit (just to get an idea of whether it is somewhat linear), and what current the led pulls.

My objective however is to be able to have it bright enough to blow away those standard 5mm led flashers but still retain decent runtime.

If I use this in my headlight I will have a switch that either has it using the circuit for flashing or switches the circuit totally out for a steady light through my current buck setup.

 

[chesterqw]

you need more then 100ma 1A!!!!

how the hell you gonna do that, i don't know

 

[joedm]

well actually I've come home and it's still going...
Anyway, I didn't measure it properly last night..

The current at the battery is between 100mA and 200mA. I can't seem to get my multimeter working using the mA plug.. but that could be because it says 200mA MAX. So I can only guess that the current fluctuates from as low as ~100mA to greater than 200mA. When I use the 10ADC plug I get readings alternating between 0.01 and 0.02. Well it is flashing I spose.

 

[joedm]

oh yeah, forgot to say thanks for the constructive feedback =)

 

[liteglow]

This is great

Old post.. but anyway is there some other circuits here that will FLASH a 3W luxeon LED ?
Need it for my RC airplane..