Build blog: 1000+ lumen mtb light.

[Damme]

Hello everyone!

I'm totally new to this forum and am eager to build myself a great light for my cycle. I live in Sweden and the days are getting shorter and shorter. At worst we only have 6h (in the south :P) of daylight per day so good lights are essential around here. :)

I have decided to use 3 x Bridgelux, probably 440lm star neutral white ( http://export.farnell.com/bridgelux/bxra-n0400-00000/led-array-440lm-star-neutral-white/dp/1692080 )

I'm not entirely sure about the 440lm or the 880lm version but I'm pretty sure that 440lm will be enough for me. I'm also not entirely sure about neutral white or warm white. I really hate the blueish white lights that some LEDs have.

The setup I'm thinking of is milling one block of aluminum there one light is focused on the road (to be used both in woods and on roads) and the 2 extra lights to be pointed somewhat straight forward. I have not thought about reflectors yet.

I'm thinking of building the driver(s) myself, I have a lot of knowledge about digital electronics, programming PICs etc, but analogue is my poor side. I want PWM controlled constant power driver. the digital part with pic and PWM signal and programming is no problem for me, but the constant current driver I don't have much knowledge about, tried to find schematics but haven't found any good ones yet. Beet looking at some IC like ZXSC300, STCS1A but don't know how to solve this yet.
The led wants constant current and constant voltage, how do I solve the voltage part? or does the circuit balance itself to the correct voltage when it finds the correct amp's ?

The power source will be a bunch of LiPo (Lithium-ion polymer) cells. They are 3.6Volts 2.6Ah each, how many is not decided yet but I want around 5h of light.

To recap;
* Will I be happy with 3x 440 lm neutral white?
* What type of reflecor(s) would fit and be good?
* PWM Constant current driver? Schematics?

So with your help in here this thread will be a build blog as I progress. And hopefully before it gets too dark outside I will be finnished :)

Thanks a lot in advance :) :cool:
//Daniel

 

[jason 77]

To recap;
* Will I be happy with 3x 440 lm neutral white?
* What type of reflecor(s) would fit and be good?
* PWM Constant current driver? Schematics?

* yes I would think that 3 "BXRA-N0400-00000" leds would be more than enough light output.

* I have been putzing around with frensel lens so far, but have been unable to find any reflectors that will work with the bridgelux series LEDs.

* Try out Dan Goldwater's constant current circuit, step eight shows how to let a micro controller "control" the constant current circuit.
http://www.instructables.com/id/Circuits-for-using-High-Power-LED-s/

Also member jeffosborne on this site has modified Dan's circuit to make it a bit more efficient than the original...

 

[griff]

Impressive first post!,

Good Luck

 

[Steve K]

The led wants constant current and constant voltage, how do I solve the voltage part? or does the circuit balance itself to the correct voltage when it finds the correct amp's ?

The led actually just needs constant current. The voltage will vary with the current applied and with the led temperature.

Ideally, you would drive the led with a switching power supply that regulates current instead of voltage.

sounds like an interesting project. I'm curious about what reflectors or optics will work with the Bridgelux leds. I had the general impression that they were pretty large and would require a large reflector or optic to focus them.

good luck,
Steve K.

 

[tandem]

I want PWM controlled constant power driver

Just a word of warning - if you also depend on a cycle computer of the wireless variety, it seems that many models of these are susceptible to RFI from PWM regulated lights.

I first noticed this problem with a Planet Bike Blaze 2W light sitting near an el-cheapo wireless bike computer. Others have reported the same problem with a variety of lights and computers. In the case of the Blaze it only occurs on low and strobe, the two modes where PWM is apparently employed. On "high" output it does not interfere with the computer.

For this reason I recently bought a current controlled light, the Fenix LD10 R4. No PWM. No RFI issues whatsoever. And it happens to be a runtime and output champion in its class... so clearly PWM isn't the only way to go.

 

[Damme]

First off, Thanks! :)

Also member jeffosborne on this site has modified Dan's circuit to make it a bit more efficient than the original...

I think I found the post, http://www.candlepowerforums.com/vb/showpost.php?p=3419062&postcount=12, is this the one you were thinking of?
I just tried some constant current but its late evening here and it all ended up in a miniature atomic bomb. I will redesign it tomorrow :)

Ideally, you would drive the led with a switching power supply that regulates current instead of voltage.

sounds like an interesting project. I'm curious about what reflectors or optics will work with the Bridgelux LEDs. I had the general impression that they were pretty large and would require a large reflector or optic to focus them.

I understand the current vs voltage and leds now.
About the reflector I have no clue yet, I might have to make something myself.

Just a word of warning - if you also depend on a cycle computer of the wireless variety, it seems that many models of these are susceptible to RFI from PWM regulated lights.

Wow, thanks for the warning, had no idea about that, but I think this is solvable with shielded cables and/or other PWM-frequency. I don't have any computer yet but I'll sure try this out and share what I learn.

//Daniel

 

[BrianMc]

Discussion of controlling Electromagnetic Interferenece EMI and Radio Frequency Interference RFI:

http://www.candlepowerforums.com/vb/showthread.php?p=3458624

I had a Xenon flash that was murder on my pulsimeter. Self contained and no room for mods, and aluminum foil on the back had no effect. Had to locate it well away from the receiver. My current setup needs a little work as I can't run the bar light on flash and have the pulsimeter right beside it work. Half power and the PWN has no effect. So, I can't use daylight strobe on the bar light. That limitation is not bugging me enough to put advice above into effect. Driver is a Taskled BFlex.

 

[Steve K]

Wow, thanks for the warning, had no idea about that, but I think this is solvable with shielded cables and/or other PWM-frequency. I don't have any computer yet but I'll sure try this out and share what I learn.

//Daniel

The EMI problem is due primarily to the fast changes in LED current. If you are creating the design, then it's not too hard to slow the rise and fall time of the current. The downside is that the transistor spends more time in the linear region, causing more power to be dissipated, but there's probably a middle ground where both the EMI and the power loss is acceptable. Once you have a preliminary design, it can be reviewed for EMI issues.

regards,
Steve K.

 

[jason 77]

First off, Thanks! :)


I think I found the post, http://www.candlepowerforums.com/vb/showpost.php?p=3419062&postcount=12, is this the one you were thinking of?
I just tried some constant current but its late evening here and it all ended up in a miniature atomic bomb. I will redesign it tomorrow :)




//Daniel

Yes that is the circuit I was thinking of... however if you read further down that thread you will find out that the circuit he posted is only part of the whole circuit, as I tried building it as well with some unwanted effects. I would try Dan Goldwater's circuit first just for something to play around with.