Cycling UK Forum

I have just purchased a Shimano 3N-80 Dynohub ( built into Wheel ) and Edelux light.

The Edelux instructions state

"If one contact of the dynamo is electrically connected to the frame (e.g.
all models of Shimano), the wires are no longer interchangeable: The outer
conductor of the coaxial cable (not insulated or covered with
black shrink sleeve) must be connected to the ground , the transparent
insulated interior wire must be connected to the phase contact of the
dynamo."

My question is do I just simply insert the transparent insulated wire into the phase contact of the Shimano ports and the remaining wire to the frame thereby earthing it ? I dont want to scrape paint off the frame to ensure a good earth though ?

If so, is it obvious which is the phase port ?

If I insert each wire into each port I assume there is no permanent damage ?

Why do you have to earth it with Shimano but not if you used a Schmidt SON Dynohub ?

Any advice / diagrams would be very helpful.

Many thanks.

I would say that it's simply that Schimdt do not provide the earthing facility and Shimano do (the reason is that it can make installing rear lights easier. You should connect the two wires to the hub, only ensuring that you do actually get them the right way round. No need to be scraping paint away, although you may possibly need to if you do install a single wired rear lamp.

The hub terminal plug will also have an earth symbol to indicate the earth contact. What is all this stuff about phase ports??? Never come across one of em before

Shimano generators have one terminal connected to ground so that must connect to the lamp ground and the 'phase' of the generator connects to the 'phase' of the lamp.

If you reverse the connections, then you are short-circuiting the generator - unlikely to damage it but the lamp won't light either!

It's bad practise (IMO) to use the bike frame as an electrical connection - just run the coaxial cable from the lamp to the Shimano and ensure the outer (ground) lead connects to the generator ground. I can't tell you which terminal is which on the Shimano, but if you get it wrong and the lamp doesn't light, then swap them round.

With the SON generator, both terminals are isolated so either may be connected to 'ground' (chassis)

If you look at the little plug thing that connects to the Shimano dynohub, you will see one terminal has the electrical symbol for "earth" in the moulding. This is the one that connects to the bit that earths to the frame. As somebody has said already, run 2 wires,( basically earth and live or "phase" as its actually an A/C alternator, not a D/C dynamo). The only snag is one terminal of lamp and generator is "earthed", so you need to connect those 2 to the same wire, or you will short circuit.

If you connect it the wrong way round it won't work. That's all. Oddly, depending on the type of bracket you use to mount the lamp it *might* work both ways round, but you should get it right anyway; I had problems with a Supernova light glowing faintly when turned off because the wires were reversed.

Thanks very much to all for the extremely helpful answers.