Originally Posted by
znomit
The cyo manual states DC is OK. Not so for the IQ-X.
From the instructions for IQ-Cyo Senso currently on my bike and powered there by DC:
Admittedly, instructions for some of the first IQ_Cyos stated that you could use the lamp with a battery, but at your own risk.
Originally Posted by
Tourist in MSN
I recall reading somewhere that someone tried DC on a Luxos U and blew the circuits, but I do not recall where I saw that or what voltage.
The B&M 2020 catalog lists two ways to power dyno powered lights with something other than a dynohub, one for testing and one for setting up a store display on page 52. The photo of the tester has a 6V notation on the device. I can't read the printing on the device to power the display.
Recently I had a Li Ion battery that somehow got overcharged, meter said 4.2 volts and I wanted to drain down the power somewhat. Based in part on seeing that 6V tester, I assumed that a dyno powered taillight would not be harmed, so I used that to slowly drain some power from my Li Ion battery, that worked just fine and it gave me a chance to see what the light pattern from the light was like. My curiosity got to me and I tried two other taillights to see what the light pattern was like on them too.
I would not start applying DC to any lights based on my comments here, but you might try to find if the instructions for either the tester or display power supply are available on line.
All LED lamps are obviously DC internally. The first thing they do with AC is that they rectify it and smooth it out. If you start with a DC and you run it through the process, you get the same outcome as when starting with AC. It is absolutely irrelevant in that sense, for the lamp interior, whether you feed the lamp with AC or DC. However, there may be a difference if the AC pulses are used for something before power delivery to the main light unit. I saw on an occasion a difference in operation depending on the polarity of DC fed to a lamp. It looked like only one polarity of AC was used to charge the standlight capacitor, maybe to limit the power taken away from the main light unit during that charging. IQ-X seems to use the pulse frequency, though, to make some decisions for the lamp, though. This seems to explain why you should use it with hub but not bottle dynamos. The latter have pulse frequency about 3x higher than hub. I normally put lamp switches in on position and decide on the lamps being on or off with outside circuitry. Having to stop to put the lamp on or off makes in itself no sense to me and a flimsy switch on a rubber band, at times, does not make sense either. I.e., if IQ-X could be put to always on, I would not care what it does with the pulses, but it seems that there is no such option for that lamp, hence my poking around with the questions pertaining to practical experiences.
As to the DC powering of front vs rear lights, the brake versions of the rear are likely to test pulse frequency, so one could expect some issues there.
As maybe one more comment, when you look at the voltage from the dynamo side on an oscilloscope, when the dynamo is loaded with a front LED lamp, the voltage has nothing to do with a nice textbook sinusoidal profile, that the dynamo yields with no load, but becomes trapezoidal and nearly square like. After rectification, it is DC with notches. Weird form of voltage is already there when you operate the dynamo system by the book.