Idiots guide to dynamos

[fluffybunnyuk]

umm im an idiot, and i need information about wiring up dynamos, and hints n tips to avoid water problems.

Ive read various stuff on here and around the net(wiring techniques, in parallel/series etc). But im sure helpful as always people will come up with sound advice.

Emma

[Brucey]

it might help if you say which dynamo and which lamps you intend to use; they vary a little so that something which is quite sensible with one might seem a bit mad with another.

cheers

[fluffybunnyuk]

shimnano DH 780 hub , and luxos u front light with usb and toplight rear light. Ive heard people talking about water ingress. So im going to cover the cables in copter tape. not a problem since im coating the frame in it anyway. But that still leaves waterproofing the lights and connections.

I have problems knowing what a nyloc nut is let alone anything technical bike related so this should be lots of fun one weekend soon.

[mjr]

Wire them up any way that the lamp manuals suggest that you like.

Never have a lamp or plug as a local low point unless it's designed for it (like some Shimano hub plugs) else the water will drip in. Put a loop below if in doubt, like with TV aerial cables where they go into houses.

I'm a fan of securing wires to cable stops, stays and racks where possible, as in http://lovelybike.blogspot.co.uk/2011/1 ... -look.html

[Brucey]

I wrote some thoughts on general installation issues here;

http://forum.ctc.org.uk/viewtopic.php?f=5&t=79518&p=700990&hilit=heat+shrink&sid=0e787231b30a6b9e467ad6187a5f8b1d&sid=0e787231b30a6b9e467ad6187a5f8b1d#p700990

which you might find useful but each installation (and bike) has its little quirks.

cheers

[Audax67]

I put Tamiya connectors in the rearlight cable at around seat-tube level so that when I take the rack off I can unplug it quickly. I filled all the holes with silicon glue, which makes it hard to plug in/unplug because of trapped air, but does make you feel sure of it. When I plug it in a bit of black tape goes round the join. These last two measures are probably unnecessary, since water is a poor conductor and the voltage so low that leakage between the connections would be practically nil. Well, there might be a bit of electrolysis.

[fluffybunnyuk]

OK, thanks for all of that. My next question is should I use the shimano overvoltage protector. Some companies say it produces dimmer lights. If Im using the Luxos U do I need this piece of kit? Its unclear if the circuit protects just the lights or the USB too.

[edocaster]

I use Tamiya connectors too, but only for a special 'accessory' connection I can plug whatever I need into. It's terminated at the stem, and rainproofed with a flap of inner tube.

The basic wiring of off-the-shelf lights is really simple. Two wires from the hub to the front light, two more from the front to the rear if needed.

As I understand it, the overvoltage protector (SM-DH10) was designed to protect rear lights should the front bulb blow - as old lights used the balance of both lights' impedance to ensure the front got 2.4W of power and the rear 0.6W, so if the front light blew the rear would be overvolted. This shouldn't be an issue with any modern LED front light, as LEDs generally don't blow. The overvoltage protector isn't there to protect the front light per se - just the rear. I'd imagine with a Luxos U and a modern LED rear light (or no rear light) the overvoltage protector won't be necessary.