Suitable 1xAA LED body for modding

Hello, this is my first post so please go easy on me, I've been a lurker for some time, I'm now coming out (I'm even telling my parents! )

I've recently purchased a Ultrafire C3 from DX( with extra tube), it turned up yesterday and for the most part I'm rather pleased with it . Seeing the output from a single AA I was most impressed, its brighter than my 3D Maglite with an EverLED and brighter than my Tesco's 3w Luxeon.

With this in mind, it got me thinking that a single AA torch with a Cree RED emitter with maybe a strobe would make for a most excellent tail light on a bicycle, but there appears to be no ready made solution on the market (at suitable low cost). With that in mind, I was hoping to pick your collective brains for options on a body that is easy enough to mod. :thinking: I've seen some fantastic tail lights made up but finding a suitable body to house it in is a pain, so I'd like to cheat

Thanks for reading

Matt said:

With this in mind, it got me thinking that a single AA torch with a Cree RED emitter with maybe a strobe would make for a most excellent tail light on a bicycle, but there appears to be no ready made solution on the market (at suitable low cost). With that in mind, I was hoping to pick your collective brains for options on a body that is easy enough to mod. :thinking: I've seen some fantastic tail lights made up but finding a suitable body to house it in is a pain, so I'd like to cheat

Thanks for reading

Click to expand...

I'd recommend that you didn't put a bright flashing red light on the back of your bike, a Cree is going to be far too bright. It will attract attention but make it difficult to work out how far away you are and especially what yourr speed and direction are.

A steady light is far safer, drivers will be able to see you the light and have a steady point of reference in working out where you are and where you're going. If you make the light too bright, it will dazzle and again drivers will see the light but not the cyclist.

A light with a few constant (i.e. not flashing) 5mm LEDs as widely spaced as possible is the best solution I can see for a bike tail light.

A few constant or flashing 5mm LEDs should be fine, or drive the Red Cree at a low current. It takes less light to be seen then to illuminate.

Also check the bicycle section.

:welcome:

Thanks for the responses. I understand that the general concensous is a few 5mm LED's but my idea is to create a low budget Dinotte style tail light with lots of output so it can be seen from space (long dark country roads) without the excessive price tag :laughing:

A few modes on a mini torch and red cree seemed to me to be an ideal solution to the problem. This should probably be in the bicycle section, sorry!

Matt said:

Thanks for the responses. I understand that the general concensous is a few 5mm LED's but my idea is to create a low budget Dinotte style tail light with lots of output so it can be seen from space (long dark country roads) without the excessive price tag :laughing:

A few modes on a mini torch and red cree seemed to me to be an ideal solution to the problem. This should probably be in the bicycle section, sorry!

Click to expand...

Humans can't judge distance to a point light source very well, so a single Cree is going to be a bad idea. Your light will be visible from a long distance away but you'll be invisible behind it. Drivers will be able to see the light but won't know how far away you are or how fast you're going. Thats a bad thing because they'll get pretty close to you before they realise they're close to you.

If you want to be safe, rather than "high tech" looking, you need to create as large an illuminated area as you can, ideally you'd illuminate your back with red light, failing that a few 5mm LEDs spaced a distance apart will give something that drivers can work out distance to. The cheap LED lights with 3 or more 5mm LEDs in them seem to work the best, I'm not a fan of the flashing ones but I have seen lights where only one of perhaps 3 LEDs flash (the rest being constant on) and that seemed to be a good compromise between flashing and constant (although I'd prefer none of the flashed).

I'm not the target cycle rider myself, its a guy in my office who expressed an interest in the idea using me for help. He does already have a rear multi LED light, refelctors, a good high visability cycle jacket with light reflectors and his amusingly-skin-tight cycle trousers have reflectors too

This would be an additional light to his armoury so to speak, the logic being super bright on the front and the rear, much like the Dinotte which get great reviews.

I get the feeling my reasoning isn't going down well :tinfoil:

I was actually thinking the same thing yesterday when walking to my bike after work. I hate those cheap multi 5mm led blinkers. I always manage to drop them on the ground causing the batteries and reflectors to fly in different directions...
I remember seeing some bullet style tail light that could be bolted on the seatstay, but I don't remember the maker.

This seems to have reasonable runtime and brightness, looks easy to mod too.

Keep in mind of course the red cree availible at DX is on a 20mm star, which would make for a rather large head on a single AA light. If this was a project I was going to make, I would look at a custom housing, not from a flashlight. I would attempt to mount the led on a small PC heatsink, maybe a graphics card sink. Mount it to a bent over piece of aluminum flat stock and find a way to diffuse it with a clear or red reflector. Hopefully that would also widen the beam. The simplest driver solution I could think of would be an amc7135 board at 350ma. For a battery solution I would probably find a 4AA holder with a cover and rewire it to hold 2X2 series parralel. At least, that is what comes to mind right away. Problems I foresee - Because of the low voltage required to drive the red cree, a significent percentage of your battery power will be converted to heat in the linear driver and wasted. And the AMC7135 drivers drop out of regulation at a low voltage, I believe it was somewhere around 1.9V. Some have suggested removing the reverse polarity protection diode. I thought they picked up an extra .5V of regulation like that, but again, I would need to check the spec sheet of the amc7135 to see and I don't have the time right now. However, it should be easy to google.

Short of that, there is a driver on DX that has a pot to adjust it. Need to find the specs on it also, but I am thinking off the top of my head it may cut the mustard. Do some research on the sku 7882 driver. Sorry I don't have time for a more thorough answer.

M.S - I've seen that one, thought it might be worth a punt in my next order as it is suitably cheap to tinker with, perhaps that would be a decent starting point

VegasF6 - I'd seen that 7882, I was thinking of using that with the 1776 Cree. The only down side to that is the excessive number of modes for this simple application but I guess I could live with it for a first build

Idealy I need an existing LED housing that can hold 2XAA, but 90% of them are AAA and as such, rather to small to cram things into. I saw one on here based on a Vistalite case, it was great but I can't get hold on those

It does seem like a lot of modes, but they are in groups. So if you keep it in group 1 you only have 5 modes. You can also make it a single mode only driver as explained on the forums here, as well as the customer comments at DX (see the post "disable the extra modes")

I have managed to use it as a single mode before, but I also managed to kill one of them.

Read through some of this post if you like:
http://www.cpfmarketplace.com/mp/showthread.php?t=169324&page=2
It talks about the efficiency, about using it as a single mode, about how the board has changed, and most importantly about the solder pad you may have to jumper. (I don't think you need to in single mode) Right around post 115 that part of the discussion starts.

I am sorry I don't know of a donor light for you that uses a 20mm led, but here is a website doing pretty much exactly what I had envisioned.
http://www.kayakaccessri.info/krabachwebsite/bike_light/bike_light_project/proto10.html


Kaidomain lista a red cree led 17mm star, that should help, but it is on back order. Also lists to other "red cree led emittor" but with no dimensions, so you could write customer service, but I have to say it is a crap shoot.

Cutter electronics also lists them, in a bare emitter, 17mm or 20mm board.

Actually, I have sku 1778, except I have the SSC version of it. It only drives the led at like 350mA anyhow, so it wouldn't even need a board change, but of course it doesn't flash. 2AA host, very thick.

Hey Vegas, thanks again for your input. I'd seen http://www.kayakaccessri.info thats were the idea I had seemed to make sense :naughty: It got the cycle guys in the office quite excited

I think I'll bite the bullet and get an emitter and a driver board, hope they are good ones and have a tinker, see if I can find a housing in the mean time. I'll add it to an order for another Ultrafire C3, which is currently my favorite torch in my little collection. I applied a red filter to the C3 the other night to see how much output it would give, its a very good red output so perhaps I can get away with using a white emitter.

I'm trying to get hold of some unwanted halogen bike lights to convert to Cree C3's at the moment, silly really, I don't even own a bicycle! :tinfoil: