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I run a SON hub dynamo and have recently upgraded my front light (the old light and the dynamo are ~10 years old). The new one is much brighter than the old and has a USB outlet for charging stuff, so I'm very happy with that (Lumotec Eyc).

What I want from a rear light is something like the "superflash" red LED lights, but any kind of blinking would be acceptable. Ideally I'd like one that has both constant and blinking LEDs but I have enough power available to run two, so I'm willing to keep my existing light.

I run my dyno lights constantly, day and night, so having an "off" switch is not necessary (and slightly undesirable), I'd be quite happy with a light that simply flashes whenever power is applied.

But with much searching I have not been able to find anything. I am specifically not interested in the "reelight" things, they will not work for me (and I recommend against them in general, they flash too slowly and too dimly). This thread on bikeradar didn't turn up anything. I suspect part of the problem is that blinking bike lights are not legal in Germany, home of all the good bike light manufacturers.

But I would love a link to one that I can buy, if anyone has one.

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I concur with the questions unhappy verdict that German law prevents flashing rear dynamo powered lights, Peter White is stronger peterwhitecycles.com/taillights.asp with his "No." –  Samuel Russell Dec 3 '13 at 2:57
    
Traditionally, blinking taillights have not been provided with gensets because the load of a blinking incandescent lamp would cause the headlight to flicker (worse than it did already). But certainly there have been blinking taillights for battery sets that could be adapted to a genset, and with LEDs the fluctuating load is no longer an issue. (This might actually be a good challenge for some teenager electronics hobbyist -- relatively cheap and straight-forward to do, with readily available parts, other than the housing.) –  Daniel R Hicks Dec 3 '13 at 4:09
    
@DanielRHicks if I was going to DIY I'd most likely take an existing blinky, remove the batteries and add a 3V regulator or DC/DC converter and run it off the front light output, which is usually a smooth-ish 5V or 6V with modern lights. In my case I have 5V 500mA available from the USB output as well. Although given how many spare blinkies I have, I'd be tempted to leave out the converter and see if one would just run off 6V :) In fact, I might just do that when I get home. A lab power supply is just like a dynamo, isn't it? –  Mσᶎ Dec 3 '13 at 4:33
    
@Ӎσᶎ, why not put several in series ;p –  Vorac Dec 3 '13 at 9:23
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@Ӎσᶎ they probably would run off 6V, most of the blinkies run off 2 lithium coin cells in series, giving ~7V. Might need a capacitor though. Even the bigger rear lights use a driver chip that has a reasonable range of input voltages, to provide their current-controlled output. I'm running the PCB of a 2AA rear light in the battery box of a 3AA head torch which I've modded to use 1 lithium AA. so everything runs of 3.6V. Works a treat. –  Chris H Dec 3 '13 at 10:50
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