Weirdness with dynamo light wiring
 

I've been using modern dynamo hubs for a dozen years, and old Sturmey Archer ones even longer. I've used a variety of lights, both home-made and factory made. I've experienced all kinds of weirdness. Usually because there's something wrong with the wiring. I'm not afraid of messing with electronics, but I have no subtle understanding of what I'm doing. I connect the wires, I try it out; if it doesn't work, I disconnect it and reconnect it and try again. Repeat until it works.

A few days ago I set up a Planet Bike Blaze Dynamo light with a new Shimano dynohub, a 6v 3w one, I don't remember the model number. Yesterday I rode to work in the dark, and it was fine. Good steady light while riding, steady but much dimmer standlight when I stopped. But today something has changed. When riding, the light flashes; a series of weak flashes, then one powerful flash, then no flash at all: so it's like

flash-flash-flash-FLASH-dark-flash-flash-flash-FLASH-dark-flash-flash-flash-FLASH-dark-flash-flash-flash-FLASH-dark

and it's really annoying.

And when I stop, the standlight function also flashes.

The light has a push button switch; it turns the light on or off. It does not appear to have multiple settings. Playing with the switch did not change the way the light was flashing.

Anyone have a theory what's going on, and how I can fix it?

Bad connection at the switch causing a short? Do you have another dynamo hub you can swap in to make sure the problem is at the light (or in the wiring) and not the hub?

Spelling is also important.
...jack off a horse...

The Planet Bike Dynamo light:
Blaze Dynamo

Does say it has a flashing mode:
Steady and Superflash flashing modes

It sounds to me like you have it in flashing mode. I'm afraid I don't own the light so I don't know how to switch modes.

Alternatively go hook it up to a 6V battery and see if it works normally. Then you'd know it's the dynamo and not the light!

That the standlight function also appears to suffer from the problem after the hub has stopped tells me that the problem is not the hub, but the light or some other aspect of it. It sounds programmed, as PaulRivers suggests. I'd check out the documentation that came with the light.

No.. Hub dynamos are alternators they put out AC not DC. the light would have a Bridge Rectifier in it

to internally convert to DC (if it needs to be so), ... a converter to USB is both rectifier and voltage regulator ..


You (RHM) emailed Planet bike yet, their import office is in Wisconsin. .. It work Steady On?

Good to know. I am obviously dynamo ignorant. I would have thought that the rectifier was in the dynamo and not the light.

Know anyone with an oscilloscope? the AC waves get more frequent and closer together the faster it spins.

Oscilloscope - Wikipedia, the free encyclopedia

That's a good point, if the cause was the wiring it likely wouldn't affect the standlight.

Thanks for all the replies!

I got the light used, with no documentation; I have emailed the good people at Planet Bike and have little doubt they'll send me a pdf at some point, but nothing yet. They have pdf's of some manuals on their website, but not this one.

You're quite right, there is a steady mode and a flashing mode. I think I knew that at some point but had forgotten it. Evidently that's part of the problem, but not the whole problem.

Playing with the light late yesterday afternoon, I determined that the switch (which is a mechanical push button) has three settings (off, steady, and flashing) and each push of the button clicks it to the next setting, after which the cycle repeats. Okay. But sometimes the 'steady' function doesn't work; and sometimes the 'steady' function works for a short while and then cuts out. After this happens, the 'flashing' function still works, but doesn't seem to work quite right. Then, after a while, everything goes back to normal, all settings work correctly. For a while. And then it starts misbehaving again. So I remain as puzzled as before.

It sounds to me like most likely defective electronics... :-/ Not wiring, but the switch or circuit board or something.

Yes, that's what I'm thinking too. The push button is dodgy. It cycles through the settings correctly, but sometimes misses the "steady" setting, so jumps from the "steady" to the "flashing" setting. At least... that's my current guess. Sometimes it seems okay.

If you bought the light from a store, I'd say return it and get another one.

If you bought it on ebay, that's kinda the risk you take, unless they'd be willing to exchange it. :-/

Oh, yeah... Trexlertown Flea Market, several years ago. SOL.

Make sure you didn't use the frame as one electrical conductor. For LED lights to get full power from the dyno hub both electrical conductors must be separate from the frame.