[OrRando] Dynamo Hub lighting/lights connection question

Andrew P. Black apblack at ownmail.net
Tue Nov 20 23:42:51 PST 2007


As far as I understand things (and this is book-learnin' only; I  
don't have one), the sitiuation is like this.

The SON dynohubs don't ground to the frame.  They have two wires  
coming out of them.  So long as you connecet both wires to the light,  
you should be good.

Yes, they do generate variable-frequency AC, but that has nothing to  
do with whether or not they are grounded.  The Shimano hubs ground  
via the axle bolt; the old Sturmey-Archer hubs, like the SON hubs,  
had two wires.  They all generate AC.

The complexity with two light arises because some of the lights,  
notably the Lumotec Oval Plus, don't insulate the current-carrying  
parts of the light from the bolt that holds them to the frame.  So,  
once you have bolted the light to your frame, the frame may become  
"live".  If you bolt on a second light, and you wire the lights in  
series, and that second light also grounds one side of its inputs,  
then you will have shorted out the first light.  This can be avoided  
by insulating the light at the mounting bolt, e,g. by using a nylon  
washer, electrical tape, or whatever.

On 20 Nov 2007, at 9:10, fitzbase at comcast.net wrote:

> Anyway, Cecil chimed in that I'd have to worry about grounding,  
> since I'm mounting the light to a rack.  A read of Peter White's  
> page seems to indicate that grounding is only an issue if I'm  
> running a primary and a secondary.  At 40 lux, I'm thinking I don't  
> need a secondary.

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