Regarding dynamos for the lights

Yep. The Dynamo is probably grounded through the case and bracket to
the frame. So all you need is one wire. I assume that you checked the
bulb with the ohmmeter function of your meter and found that it was
open...

In article <[email hidden]>,

Jose Capco said:

Dear NG,

I just made my front light kaputt, and I didn't fixed it for quite a
while. Last weekend the thought of fixing it popped in my head. So I
went to the bicycle garage and checked how it looks like. I have to
change the front lights. But something confused me... I first thought it
would be good to check if the dynamo is ok.. so I took a voltmeter (I
dont have much equipments at my new place.. so..) and saw that the
dynamo is working well.. but the thing that confused me was that the
front light needs only one wire.. (I mean you usually needs two ends of
wires to connect it to the lamp to have a closed circuit!). Im not very
familiar with bicycle lights, ... does this mean that the light has the
bicycle frame as the ground? (ie.. would the other "wire-end" be
actually the bicycle frame?).. Im confused because the wiring of my
dynamo is cut off.. so I have to attach two wires to each ends, one wire
I know I will attach to the wire that connects to the front light.. but
what about the other wire? pity that I have no picture of the dynamo to
ask further question (regarding the wiring... but maybe Ill take a
picture and ask it here if my wiring dont work)

Sincerely,
Jose Capco

PS: My bike is just a simple bike and so is the lamp and the dynamo.. no
high-tech gadgetry..

Yes, the frame provides a path for the current. Not all headsets
provide electrical continuity, however. I think that some Shimano sets
incorporate plastic parts.

--
Ted Bennett
Portland, OR

Jose Capco said:

I just made my front light kaputt, and I didn't fixed it for quite a
while. Last weekend the thought of fixing it popped in my head. So I
went to the bicycle garage and checked how it looks like. I have to
change the front lights. But something confused me... I first thought it
would be good to check if the dynamo is ok.. so I took a voltmeter (I
dont have much equipments at my new place.. so..) and saw that the
dynamo is working well.. but the thing that confused me was that the
front light needs only one wire.. (I mean you usually needs two ends of
wires to connect it to the lamp to have a closed circuit!). Im not very
familiar with bicycle lights, ... does this mean that the light has the
bicycle frame as the ground?

Yes, most dynamo systems use the bicycle frame as one of the
connections. There's generally a pointed screw or sharp point
included on the mounting plate that cuts through the bike's paint
and makes good electrical contact with the frame.

(ie.. would the other "wire-end" be

Quoted message said:

actually the bicycle frame?).. Im confused because the wiring of my
dynamo is cut off.. so I have to attach two wires to each ends, one wire
I know I will attach to the wire that connects to the front light.. but
what about the other wire? pity that I have no picture of the dynamo to
ask further question (regarding the wiring... but maybe Ill take a
picture and ask it here if my wiring dont work)

Some dynamos have two separate connections for the headlight and
taillight while others just use one connections and both wires
go to that.

A picture of yours would help clarify since there are many different
designs.

Jose Capco said:

I just made my front light kaputt, and I didn't fixed it for quite a
while. Last weekend the thought of fixing it popped in my head. So I
went to the bicycle garage and checked how it looks like. I have to
change the front lights. But something confused me... I first thought it
would be good to check if the dynamo is ok.. so I took a voltmeter (I
dont have much equipments at my new place.. so..) and saw that the
dynamo is working well.. but the thing that confused me was that the
front light needs only one wire.. (I mean you usually needs two ends of
wires to connect it to the lamp to have a closed circuit!). Im not very
familiar with bicycle lights, ... does this mean that the light has the
bicycle frame as the ground? (ie.. would the other "wire-end" be
actually the bicycle frame?).. Im confused because the wiring of my
dynamo is cut off.. so I have to attach two wires to each ends, one wire
I know I will attach to the wire that connects to the front light.. but
what about the other wire? pity that I have no picture of the dynamo to
ask further question (regarding the wiring... but maybe Ill take a
picture and ask it here if my wiring dont work)

As with cars and motorcycles, the current flows from the
dynamo terminal through the wire to the lamp. Return is
through the lamp bracket to the frame and from the grounding
screw in the dynamo bracket back to the dynamo case.

If your bike has a nylon headset or a shock fork or a carbon
frame or fork or some other non-metallic current barrier,
using a double wire works well. One wire from dynamo
terminal to lamp terminal. The second wire from dynamo mount
to lamp mount.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

Jose Capco said:

... the thing that confused me was that the
front light needs only one wire.. ... does this mean that the light has the
bicycle frame as the ground?

As others have stated, most dynamos - especially older designs - use the
frame as a ground.

I'll add this: It's better not to do that. You'll get a more reliable
setup if you run twin wires. I usually use wire intended for stereo
speakers, but lamp cord works well too. One goes from the generator
output to the headlight input. The other just goes from a screw on the
generator body to a screw on the headlight body.

But don't mix them up! If you do, there won't be any damage, but there
won't be any light!

--
--------------------+
Frank Krygowski [To reply, remove rodent and vegetable dot com,
replace with cc.ysu dot edu]