3x3 Rebel Bike Light

[BillyNoMates]

I thought I would post some info on my home made Bike Light that I have been using this Winter for those who are interested in this sort of thing.

It uses an 3x3 array of Rebel LEDs, each driven independently by a LTC3454 driver. The LEDs are focussed with a mix of Ledil optics (3, 5 9 and 15 degree) which gives a good mix of flood and throw.

The system is operated with a single 'tactile' pushbutton and a PIC micro controller to manage the different brightness modes. I have currently implemented two flash modes and four brightness settings. The brightness modes are separated by factors of 3 in terms of equivalent power:

• 1 LED at 250mA
• 1 LED at 750mA
• 9 LEDs at 250mA
• 9 LEDs at 750mA.

I am using the 80lm neutral white bin for this light, which I have found gives a very good colour rendering performance (especially at the 250mA drive level). With this light, grass actually looks green (I have found that conventional cool-white with the strong blue hue is very poor for this). If I assume I am getting about 160lm per led at 750mA, then I should be getting about 1400lm in full mode.

For power I use 6x2.2Ahr LiPo cells wired in parallel (I sourced the cells from a remote control place). I've not tested the run time yet, but I should get close to 2 hours on full power.

Anyone familiar with the Rebel LED and the LTC3454 driver will realise that these are not the easiest components to mount - I opted to do a custom PCB for the circuit.

Unfortunately I didn't spend quite the same time on the case (I really wanted to start using the light), so this part looks a bit 'Heath-Robinson' - but it is functional.

Pictures below (no night-time beam shots yet, I can add them later if anyone wants to see them).

 

[jeffosborne]

Hello BillyNoMates, and welcome to the forum!

I am a fan of the Rebel LEDs, and you have made good use of them here. I wonder, how are they heatsinked? Also, are your batteries mounted in a separate pack, or in the light fixture? We would love to see the insides, yes we would. Did you program the pic yourself?

Good work, sir!

Cheers,

Jeff O.

 

[Gunnerboy]

Holy Moly!! That's bright head-on!


:welcome:

 

[BillyNoMates]

Hello BillyNoMates, and welcome to the forum!

I am a fan of the Rebel LEDs, and you have made good use of them here. I wonder, how are they heatsinked? Also, are your batteries mounted in a separate pack, or in the light fixture? We would love to see the insides, yes we would. Did you program the pic yourself?

Good work, sir!

Cheers,

Jeff O.

Hi Jeff

The LED's are mounted on a 1.6mm thick PCB (FR4 substrate). The 'thermal pad' on the rear of the Rebel is soldered to a floodfilled copper plane and I rely on several plated-through holes to transfer the heat to the rear of the board. I simply copied the recommended design in the data-sheet from the luxeon assembly guide which estimates the thermal resistance at about 12degrees/W (per led). The rear of the board is also flood-filled and fitted to the back is a large heat sink with a rating of 2degrees/watt.

Batteries are held in a separate pack which mounts on the handlebar central stem - capacity is about 48WHr and they weigh in at about 330g.

I'll try to get some piccies of the insides for you next time I fiddle with it. I did the PIC programming myself - all the Software is free from Microchip and the programmer cost less than the LEDs (so I consider it to be cheap). Using the PIC is a lot more flexible than discrete logic. There is an ADC built in which I use to monitor the supply voltage. This is used to drive an indicator LED on the top of the case next to the button and also to fall-back to minimum brightness setting if the battery is running low. This doesn't happed for the HID-based lights used by some of my work-colleagues - their lights just go out. At least I can limp home with enough light for an hour or so.

On a similar topic, I've also got a similar design with 5xRebels based on the Ledil RER-5-M lens. In addition to the usual neutral white, I have versions with red Rebels for this which I can use as a 'super-bright' rear light. I'll post more on this when I get the case sorted (I'm spending more time on that one!).

 

[BillyNoMates]

I have been busy with the camera and I thought I would share some of the pictures.

First I have taken some shots of the blank PCB I had made for this project (it's a spare which I may build up into a second unit at some point). The LED and inductors for the drivers sit on the top side. The plated through holes conduct the heat to the rear for heatsinking.

On the rear, the power converter chips + associated passives sit near along the top edge, the PIC controller and programming head fit on the left below the converters. The large shiny area is where the heat sink goes.

I've also done a couple of beam shots. These aren't the best quality photos (shakey hands - it was cold!!), but I think they give an impression of the amount of light available on full.

The house at the bottom of the hill is about 125metres away in this photo. Certainly plenty of light to see with.

 

[Bandgap]

Congrats on lovely PCB.

I understand the must-cram-it-in-a-box-and-run-it-NOW desire.

Years ago I ran with a load of 5mm amber blue and green leds (before white leds happened) on a pcb taped inside the bottom of a plastic drinks bottle.

Steve

 

[BillyNoMates]

Congrats on lovely PCB.

I understand the must-cram-it-in-a-box-and-run-it-NOW desire.

Years ago I ran with a load of 5mm amber blue and green leds (before white leds happened) on a pcb taped inside the bottom of a plastic drinks bottle.

Steve

Now that I've been using it, I'm reluctant to go back to my older setups. I hope it will last until the light evenings come back. Then I can think about sorting better case for it.

 

[toby_pra]

Very nice mod and very bright!

And welcome to CPF!:wave:

 

[bretti_kivi]

nice light!

What about running 7 in a hexagon shape- you'd probably be able to squeeze them into a 60mm round tube then.....

Bret

 

[BillyNoMates]

nice light!

What about running 7 in a hexagon shape- you'd probably be able to squeeze them into a 60mm round tube then.....

Bret

Yeah, I'd thought of that one, but I had already sourced a selection of square optics (from Brum on CPF marketplace). The orginal plan was to do a 2x2 array, but I sort of got carried away and ended up with 3x3 (I wonder how that happened ....???).

The existing PCB is about 70mm*80mm. Doesn't sound too big on paper, just looks big and ugly on the front of the bike.

Already wondering what should come next..... Anyone done a 7up MC-E??? Should fit in a 50mm round tube with the right optics !!!

 

[bretti_kivi]

i was also thinking about that; but not an MCE, rather XR-Es, 7 of them, and running the fraen optics available from led-tech for €2 each. That's also a 7 degree optic, which should be good for throw.
I'm into this for a colleague who wants something for his high-speed cross-town commute.
What batteries are you using?

Bret

 

[BillyNoMates]

i was also thinking about that; but not an MCE, rather XR-Es, 7 of them, and running the fraen optics available from led-tech for €2 each. That's also a 7 degree optic, which should be good for throw.
I'm into this for a colleague who wants something for his high-speed cross-town commute.
What batteries are you using?

Bret

I am using LiPo Cells I bought from an online Remote Control Helicopter supplier. I bought a pack with 6 cells rated at 2200mAHrs each. I 'modified' the pack to connect all the cells in parallel - the drivers I use are designed for single cell voltages ( 3.7V ). The overall size of the pack is about 50x30x100mm and weighs about 330g.

My journey to work takes about 1hr30m and I charge the batteries every two journeys. I don't use the light on full all the time - just on the empty unlit rural roads - it is a bit anti-social on full power when other road users have to look into the business end !!

Good luck with your project. Hope to see it posted here sometime in the future.