CdCf

I just had an idea, and I wanted to check with people who know more about electrics and electronics if it could work well.

Take a bright headlight with blue/white LEDs, the kind with small lenses that focus the light for even more brightness. Replace blue/white LEDs with red LEDs of similar power/voltage.

Wouldn't this make for a pretty damn bright taillight?

And before you recommend existing products that do the same, just let me remind you that they're not available where I live. Otherwise I wouldn't even be contemplating this kind of conversion.

Cyclist0383

Today you can order parts from all over the world. It shouldn't be a problem for you to order exactly what you want, provided it is currently produced.

I'm in Latvia and I order my hard to find parts from Germany, the UK, the US, and Canada. I've never had a problem.

CdCf

Yes. Anything is possible if you want to pay for shipping than the product actually costs, and if you're prepared to be unable to return a defective product without paying for shipping again.

So, while it is possible in theory, it's not viable in practice. As I said in my original post, precisely to avoid any straying from my actual question, wise as I am from past experience here.


My question wasn't how to order, but if this kind of conversion is doable.

Cyclist0383

I don't want to get in an argument with you, but in my experience shipping has never been that much, and companies have always honored their warranties (NiteRider, Arkel, Sigma Sport, and Cateye) with a minimum of hassle and expense, save for Magnum/Onguard lock which I had to fight with to get a replacement.

If you are dead set on a homemade version (you'd have to order the LEDs anyway, no?) I wish you the best of luck and reliability with your project.

CdCf

Sorry to sound so harsh before, but I'm just so tired of having almost every thread end up the same way and never getting my actual question answered.


No, I'll get the LEDs from a store 8 km from here. They have virtually everything you need in electronics. I just checked, and they have about 50-100 different models of red LEDs alone.

The total cost for the conversion would be maybe $15-20 for the light and then another $2-3 for the LEDs.

Cyclist0383

I just took apart a dead LED that I have and I don't see how this could easily be done as the LEDs are soldered to the circuit board. It seems to me you would risk damaging the board by removing and reinstalling LEDs.

CaptainCool

If you know how to solder, that's a ten-minute job. But if you can solder, you might as well make your own light from scratch. The only problems with that are a weatherproof case and a mounting bracket, and those are easy to solve.

Red LEDs have a lower forward voltage than white, so you'll either need additional resistors in line or LEDs capable of handling more current than the stock whites. You'll get more life out of a set of batteries though.

Or you could just get a scrap of red gel from anyone who does lighting. Free, quick, and probably decently effective.

CdCf

Of course I know how to solder. Otherwise this project would be impossible.

Maybe I'll build my own instead. A piece of PP pipe and a piece of Plexiglass with a rubber seal should be good for that. Just have to figure out how to get some form of lens into the whole thing.

n4zou

Forget the lens, as the LED's are already red. Just take a standard reflector and carefully drill holes in it so the LED's will fit snugly and can be held in place on the backside of the reflector with RTV or hot glue. After gluing the LED's in place slide some insulating tubing (called spaghetti) or very small Heatshrink over the leads coming out of the LED's and solder as required to each other and your resistor. After testing to make sure it all works RTV or hot glue over all of it along with a mounting screw to fit your reflector bracket. Purchase a battery box and switch and clamp it to a convenient place. You can get really fancy and mix very bright LED's and not so bright LEDs alternating around the reflector and incorporate a switch on your brake caliper so you have a nice brake light and a tail light.

CdCf

The lens is of course a clear, convex lens to focus the light for more "punch" at a distance, not a coloured one.

ken cummings

Good idea above for do-it-yourself DIY. A problem I see for using a headlight for a tail light is that it would put out a narrower beam directly to the rear. Side visibility would be poor. A good tail-light has a 180 degree angle of visibility or better. If you make one of those red reflector with red LED tail-lights consider making a curved or even a half-round one. If Swedish law permits a Xenon strobe would be even better. My xenon strobe cost $15, can be seem in day-light, and draws abount 1 watt.

CdCf

1. This would not be the only rear light. It would be an additional light to provide a stronger light for distant vehicles. A "wide" and bright 3-LED light will be used as well.

2. A reflector is wasted on a LED, since it only radiates light in a narrow cone through its "top".

3. I hate blinking/flashing lights, and they're also dangerous, so they're out of the question. No blinkie will ever be found on any of my bikes.

operator

Explain #3.

It's almost UNIVERSALLY known that blinking red LEDs on the rear means bicycle around here.

HillRider

Can you find a red filter to fasten over the current white light? A piece of red plastic or glass coud be cut to the right diameter and taped or otherwise fixed in place.

tellyho

Yeah, I love my blinky!

seriouslysilly

Even if you weren't so adapt at de-soldering and re-soldering one can go about it an easy way. Trim the legs of the led and solder the new led to the existing leg. This way you wouldn't have to bother with desoldering

n4zou

Blinking lights at night will cause depth perception problems for most people, especially Cagers looking at you through a windshield. Never blink your lights at night unless you have a steady on light to go with it so they can figure out how far or close they are from you. I run a steady red taillight, steady white headlight, and blinking amber lights all around.

Bill Kapaun

Just a hint on the LEDs in case you don't know-
Put a resistor on each LED. This prevents some of the LEDs from "hogging" all the current from the others. Probably about 1k. That would give about 10 ma assuming 12V supply. Vdrop is about 2V on the LED. I wouldn't exceed 50-60 ma per LED unless you have the documentation for the LED that shows greater current carrying capacity.
You might do a few tests at night to see how far you can see the lit LED at a few different current settings to determine the best power/light ratio. (do 5 @ 40ma appear brighter than 4 @ 50 ma etc.)

CdCf

LEDs don't emit a full spectrum, so there might be very little or no red light to pass through the red filter. In any case, the little red light there is, would be very weak compared to a true red LED.

I'm aware of this, although not in any detail. I'll have to start with checking what LEDs they sell where I plan to buy them.

froze

Speaking of red filters, you can buy red tape made specifically for automotive tail lens to fix holes; you could get a small roll of that and see if it works. You would only be out about $1 and might some day need it if you bust a tail lens?

CdCf

Good idea! I'll check if they're available over here.

JanMM

No one sells LED taillights in Sweden? If not, then, a red filter over an LED headlight would make sense.

Niles H.

I think that what you are trying to do can be done, if you choose the right bulbs; but there may be another approach to consider: If you put some translucent red film (tranparent plastic with some red colorant in it) over the lense, it might be worth a try. See what happens. It might be even better to insert the film inside, between the LEDs and the lense.

CaptainCool

The vdrop you mention is the forward voltage, and it's different for different types of LEDs. Red, green, and yellow have forward voltages of 1.5-2V; blue and white are more like 3-3.5V. This means that a straight replacement of red for white could have a big increase in current.

Maximum current for most 5mm LEDs is around 30ma, but of course there are bigger ones. I don't know how much power makes a bright taillight.

Both forward voltage and maximum current are specs on the LED. You should be able to get these when you buy.

You're right; I forgot how blue a white LED is compared to incandescent. Pretty graphs: https://en.wikipedia.org/wiki/Light-emitting_diode

Michel Gagnon

If you know how to read the specs and where to find proper red LEDs that would be compatible with your headlight circuitry, then do it. But for the less electronically minded, there are a few ready-made taillights that do just about that.

I have attached two photos:
– The first photo (the brightest one) I have shows a few taillights as seen on axis.
– The second one shows them about 20 degrees off axis, which is about what would happen when a car is about to pass you. Both photos were done – on purpose – at the same exposure : 0,01 s and F8.

On each photo, top to bottom :
– BLT Rear Super Doppler, which is almost a headlight. I hear that Serfas makes a similar one (#1000, I think).
– Cateye TL-LD1000
– Vistalite Super Nebula (a 5-LED taillight that was one of the brightest available 3 or 4 years ago)
– Planet Bike Super Spot.

All lights were aimed horizontally and in the axis of the bike, and all were using new batteries.

The only drawback of the BLT is that it can be used only on the seatpost. While it would technically be possible to use the small collar and attach it behind the rack or on a seat stay, it takes too much space behind the attachment point, so it would break easily.