dynamo lighting wires

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andrew_s
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Re: dynamo lighting wires

Post by andrew_s »

Brucey wrote:if you look at a shimano generator you will see that one connection is silvery coloured and grounded (the locknut bears directly against it), and the other one is copper coloured and is the 'live' connection.

as shown on "this image from SheldonBrown"

If either lamp has a proper ground connection via its mountings (and many do...) then it is vitally important to observe the correct polarity when wiring the lights up.

Almost all dynamo lamps earth to the mounting point - they wouldn't work with single wire connections otherwise.
However, you can mount them using a non-conducting mount such as the B+M handlebar bracket. If you use such a mount, cable polarity doesn't matter, otherwise it does.
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honesty
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Re: dynamo lighting wires

Post by honesty »

Right front and rear light turned up today. Some charge on the front line so I can test the front light position which looks good. Came with cable to connect rear light, so I've ran that I assume correctly. A few questions.
1. this is going to sound dim, but positive to positive, negative to negative right?
2. What is the little black switch on the right hand side of the rear light? (toplight line plus) I assume the red button on the other side is to discharge the light straight away, but the black lever doesnt seem to do anything. The translation I can get out of the B&M site really doesnt help me!
3. Im assuming that the rear light isnt coming on at the moment as there is not enough juice from the internal battery on the front light to charge it. Im hoping that when I connect the dynamo it will light up properly, correct?
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meic
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Re: dynamo lighting wires

Post by meic »

My Seculite rear light runs from the dynamo if the front light is switched on.
When you switch the front light off, or the dynamo stops producing it runs off its condensor until it runs flat. You can not really turn it off.
With just the front light turned on and nothing coming from the dynamo and a flat rear condensor you get no light, the front keeps it all for itself.

Yes positive to positive.

I dont know about the other switch, could it be to open the entry holes for the wires?
They often have a choice of using connectors or opening the ports and putting in bare wires then closing the ports to grip them.
Yma o Hyd
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honesty
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Re: dynamo lighting wires

Post by honesty »

meic wrote:My Seculite rear light runs from the dynamo if the front light is switched on.
When you switch the front light off, or the dynamo stops producing it runs off its condensor until it runs flat. You can not really turn it off.
With just the front light turned on and nothing coming from the dynamo and a flat rear condensor you get no light, the front keeps it all for itself.

Yes positive to positive.

I dont know about the other switch, could it be to open the entry holes for the wires?
They often have a choice of using connectors or opening the ports and putting in bare wires then closing the ports to grip them.


This makes sense, and makes the mangled German translation from the B&M website make sense as well. As I've used the connectors I can just close the lever and ignore it.
Brucey
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Re: dynamo lighting wires

Post by Brucey »

andrew_s wrote: ....Almost all dynamo lamps earth to the mounting point - they wouldn't work with single wire connections otherwise...


agreed, that used to be the case, but many front lights for hub dynamos are often quite different from ones meant for tyre driven generators; as well as having twin wiring provisions and switches, they often lack a direct ground connection, i.e. they are not intended to work with a single wire system, ever.

Also, confusingly, some rear lights have an apparently similar twin wiring provision yet still have a (non obvious unless you take it apart or test for continuity) ground connection through one of the bolts.

There are several traps for the unwary!

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
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simonineaston
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Re: dynamo lighting wires

Post by simonineaston »

I've just received a couple of metres of coaxial cable to make up my own wiring, from dynohub to B&M front lamp, via my eWerk. The strands don't look like copper - any soldering tips from you experts out there - or should I follow a tip I got off of a Quad engineer (Quad as in hi-fidelity audio equipment) which was, "soldering's just to make sure it all stays in place - it is much more important to make sure you have a good mechanical connection..." which presumably is what crimping is all about... advice please!
Is it copper? Doesn't look like it!
Is it copper? Doesn't look like it!
S
(on the look out for Armageddon, on board a Brompton nano & ever-changing Moultons)
tatanab
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Re: dynamo lighting wires

Post by tatanab »

It looks like tinned copper wire to me. It will solder easily.
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simonineaston
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Re: dynamo lighting wires

Post by simonineaston »

Hoorah! :-)
S
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andrew_s
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Re: dynamo lighting wires

Post by andrew_s »

If you use coax for dynamo wiring, it's usual to use the core for the live connection and the outer for the earth connection. That way round, if the outer insulation wears through on some bit of the frame, your lights don't go out.
rmurphy195
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Re: dynamo lighting wires

Post by rmurphy195 »

Whatever else you do its worth applying a bit of electrical connector cleaner spray to any terminals every now and again
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MikeF
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Re: dynamo lighting wires

Post by MikeF »

honesty wrote:Right front and rear light turned up today. Some charge on the front line so I can test the front light position which looks good. Came with cable to connect rear light, so I've ran that I assume correctly. A few questions.
1. this is going to sound dim, but positive to positive, negative to negative right?
2. What is the little black switch on the right hand side of the rear light? (toplight line plus) I assume the red button on the other side is to discharge the light straight away, but the black lever doesnt seem to do anything. The translation I can get out of the B&M site really doesnt help me!
3. Im assuming that the rear light isnt coming on at the moment as there is not enough juice from the internal battery on the front light to charge it. Im hoping that when I connect the dynamo it will light up properly, correct?

You may have already found this out by now. The wire with the white stripe denotes the earth/frame (negative sign wire). Connect wires with the same colour together. The switch on the underside of the rear light on mine allows me to turn that light off eg when parking the bike - but will not switch it on. You need to use the generator to do that. It does not discharge the capacitor. The other lever is used to clamp the bared ends of the connecting wires when you've pushed them into the holes. Alternatively you can connect the wires to the light via the spade connectors. If the rear light doesn't work you may need to check your connections and also the wires match.
"It takes a genius to spot the obvious" - my old physics master.
I don't peddle bikes.
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mjr
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Re: dynamo lighting wires

Post by mjr »

As agreed in viewtopic.php?f=5&t=86312 white stripe is not earth on all lamps: check instructions.
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
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