Can someone help me pick an LED for a DIY dynamo taillight?
 

Hey everyone!

I recently set up my bicycle with a Shimano DH-3N80 front hub, and the Supernova E3 Pro 2 headlight.

There are many good things to be said about the Supernova E3 headlight- however, taillight selection is not one of those things. I have no love for the taillight mounting options Supernova provides- I like fender mounted lights much more. Unfortunately, Supernova recommends that you only use their taillights with the E3 headlight.

I found a website detailing a method for constructing your own taillight to go with the E3 headlight.

Red Giant LED Tail light

This idea is very appealing to me. I currently have a PDW Fenderbot taillight, and I'd like to put an LED behind the reflector in it, much like in the link above. I don't like the idea of using a white LED in the taillight, however, and I also don't have to deal with quite the same space restrictions as the instructions in the link above, since I'm not trying to put an LED into such a small, flat reflector.

Can someone help me select an LED that would be both 1), more appropriate for this project, and 2), red?

I've never done anything like this before, but it seems like a relatively easy project, and much cheaper than Supernova's offerings.

Any advice on the matter would be greatly appreciated!

Thaaanks!

Try this one, its a red XPE, will handle about 500mA if you want to push it.

SingFire 180lm Red Light LED Emitte On 16mm Star - Free Shipping - DealExtreme

Wouldn't that be too high power for the dynamo? Dynamos typically are rated at 3W, no?

[TABLE]
[TR]
[TD]Brand[/TD]
[TD]SingFire [/TD]
[/TR]
[TR]
[TD]Model[/TD]
[TD]SF-R2R [/TD]
[/TR]
[TR]
[TD]Color[/TD]
[TD]White [/TD]
[/TR]
[TR]
[TD]Quantity[/TD]
[TD]1 [/TD]
[/TR]
[TR]
[TD]Material[/TD]
[TD]Aluminum [/TD]
[/TR]
[TR]
[TD]Emitter Brand[/TD]
[TD]CREE [/TD]
[/TR]
[TR]
[TD]Emitter Model[/TD]
[TD]R2-N4 [/TD]
[/TR]
[TR]
[TD]Output Power[/TD]
[TD]3W [/TD]
[/TR]
[TR]
[TD]Luminous Flux[/TD]
[TD]180 [/TD]
[/TR]
[TR]
[TD]Base Size[/TD]
[TD]16mm [/TD]
[/TR]
[TR]
[TD]Driving Current[/TD]
[TD]1000mA [/TD]
[/TR]
[TR]
[TD]Voltage[/TD]
[TD]2.3-2.5V [/TD]
[/TR]
[/TABLE]


Despite the description saying 3W. 2.3-2.5V multiply 1000mA isn't 3W.



DIY website you linked to and the RADbot has ZERO heatsinking. I recommend some heatsinking at least.

You don't need to run the LED at full power (the resistor in the circuit limits the power draw), and no dynamos aren't rated at 3W, 3W is what they deliver when hooked up to the traditional incandescent bulb.

Bubbles; DX product descriptions are usually screwy. Pretty sure thats a cree XPE, Vf ~ 2.3V and max current 700mA. Yes, heatsinking is a good idea but at 150mA you might get away without it. At least move the resistor out of the case.

OP, You probably want to use two of those LEDs (will better match the 6V from the light). You can get a board with 3 on them from cutter.com.au. Not sure why Supernova say not to use another tail light, there are plenty out there... Maybe a too high power draw will kill the headlight? Have you emailed them to ask and pointed out your reasons?

" 12mm 1.8V~3V Red LED Emitters (20-Pack) " without the aluminum heat sink disc backing of Cree type. is on the same site.

DIY search, more maybe 5mm are there too..

there was a thread here recently where we talked about a taillight for supernova. They rectify the voltage which includes the standlight. So they probably don't want to be responsible for helping make other lights work. I still haven't tried it, but another poster said that a B&M light works if you hook it up right. The supernova lights appear to be very simple, 3 leds and some resistors. Although I've never been able to verify this from the pictures I've found online

This suggests to me either the website should not be followed slavishly, or that the light designer did not expect a current draw greater than maybe 150 ma.

I'm not sure that the supernova headlight is really guaranteed to put out less than 6v, but assuming it is and a 2v Vf on the LEDs, the website is calling for no more than 1/2 watt across the tail light LED. The supernova tail light has no heat sinking, but I'm not sure how much current it draws at 6 v. The LED at the website in the OP actually has a certain amount of heatsink built in. Granted, it wouldn't work for a headlight, but it would almost certainly work in this application.

Awesome! I feel like you're picking up what I'm putting down.

That said, uhh... would that LED znomit posted work, or does that one demand too much power? Would there be a better option? Or is that a good one?

I'm really new to DIY lighting and I'm more confused now than when I started.

If I need to fit some sort of heatsink in the reflector shell of the PDW Fenderbot I'm certain I can figure that out. I don't need the light to be super powerful, though. Just a happy lil' taillight.

Thanks for the help so far, everyone!

if you can fit that star into a fenderbot, the led that znomit recommended will be fine. That is plenty of heatsinking at the currents you will be feeding it

On a totally different tack, I would probably try to get one of the dyno Spaninga Pixeos to work. People love those things. Make sure it's not the battery powered version and you should be fine.

If space is a concern (and price is not) heres one on a 10mm base. Maybe get two.

Cutter Electronics - Suppliers of Cree Leds, lowest cost leds on the internet

Heres the 3 led addressable 20mm board (you can wire two in series).
Triple (3-Up) Cree XLamp XP-E2 High Power LED Star

I finally got back into this project! I was originally going to go with the Cutter-XPE-10R-PR, but shipping to the US was a prohibitive $25.

Instead, the Triple (3-Up) Cree XLamp XP-E2 High Power LED Star Znomit linked to seems like a great choice. When he said I could wire two in series, was he talking about two of the LED's on that board, or two of those LED Stars? I'm assuming the former.

I'm very new to wiring electronics, but excited to try this project. Are there any other small, red single-LED's I might have an easier time wiring up than that star?

Finally, I'm also assuming any resistor marked as a 1/2 watt, 12 ohm resistor will work. Is that correct?

Thanks again, everyone. Once I get this project done, I'll be sure to share picture with you.

Yes, just use two of the LEDs to keep under 6V! So you'll need to remove one of the zero ohm resistors (the Cutter board is a bit easier to use in that respect).

It sounds like you know what you want to do, but Velo Orange just came out with some cool mounts for the E3 tail light.

http://4.bp.blogspot.com/-SF5WA6xvAM...ge%2Bmount.png