Schmidt SON / Light wiring question

In article <[email hidden]>,

BobT said:

I am making plans to install lights on my new touring bike and
connect them to a Schmidt hub dynamo.

In researching this, I note that the Schmidt lights are supplied
with "heavy duty coaxial cable" to connect to the dynamo. Why would
shielded coaxial cable be needed to connect up a hub dynamo and
lights?

I don't know that it's "needed," it's just the wiring used by Schmidt.

Quoted message said:

My current bike has a Shimano Nexus hub dynamo and a B&M Lumotech
light that came from the bike factory wired with small gauge, simple,
paired, parallel, zip type, cable.

I use a Lumotech Oval Plus with my Schmidt SON (both came indirectly
from PJW via a local bike shop). It also is wired with coaxial wire.

Quoted message said:

For my application (tail light and two independently switched front
lights), I want to modify the wiring harnesses that come with the
lights. I am wondering if it makes much difference what wire I use
in this 6 volt, 3 watt system?

Hmmm. Except you're setting up more than 3W of power consumption- 5.4W
or 6.6W. You'll want to check and make sure you'll have enough juice to
run them all- at low speeds in particular.

"Tim McNamara" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Hmmm. Except you're setting up more than 3W of power consumption- 5.4W
or 6.6W. You'll want to check and make sure you'll have enough juice to
run them all- at low speeds in particular.

I've found several descriptions saying this will work - at Peter White's
site:

http://www.peterwhitecycles.com/wiringinstructions.asp

and here:

http://www.m-gineering.nl/son12vg.htm

The Schmidt dynamo functions as a constant current device. You connect the
2.4 watt primary headlight (B&M Lumotec N Plus in my case) in parallel with
the 0.6 watt tail light (I'm using a B&M DToplight plus). You then connect
the secondary 3 watt headlight (I'm using a Schimdt E6-z) in series with the
other lights. With this setup, the dynamo produces 12 volts, 6 watts when a
speed of about 10 m.p.h. is reached and powers all three lights
satisfactorily. If riding continually at a slower speed, one switches off
the secondary light because I'm told that one fully powered light is
brighter than two under powered lights.

Back to the wire question: I assume (often a mistake) that in this
sophisticated, German engineered dynamo / light system, if coaxial cable is
used it must be for some good reason, but what reason?

BobT

BobT said:

Back to the wire question: I assume (often a mistake) that in this
sophisticated, German engineered dynamo / light system, if coaxial cable is
used it must be for some good reason, but what reason?

Most likely the reason is psychological, not physical.

It could be "good" in the former case, but not in the latter!

bob prohaska

Quoted message said:

BobT said:

In researching this, I note that the Schmidt lights are supplied
with "heavy duty coaxial cable" to connect to the dynamo. Why
would shielded coaxial cable be needed to connect up a hub dynamo
and lights?

AFAIK Schmidt looked for a cable that is UV resistant, robust,
convenient to run and offers two times a sufficient cross section.
The supplied coaxial cable meets that specification, standard 2 way
cable with sufficient cross section typically is no longer round or
pretty thick...

--
MfG/Best regards
helmut springer

BobT said:

I am making plans to install lights on my new touring bike and connect them
to a Schmidt hub dynamo.

In researching this, I note that the Schmidt lights are supplied with
"heavy duty coaxial cable" to connect to the dynamo. Why would shielded
coaxial cable be needed to connect up a hub dynamo and lights?

It is strong, wearresistant, easy to route and elegant. That it happens
to be coaxial (which is more work to nstall) is something you have to
take with the advantages

--
---
Marten Gerritsen

INFOapestaartjeM-GINEERINGpuntNL
www.m-gineering.nl

BobT said:

Back to the wire question: I assume (often a mistake) that in this
sophisticated, German engineered dynamo / light system, if coaxial cable is
used it must be for some good reason, but what reason?

BobT

I haven't looked at the schematics so this is merely speculation:

1) one reason could be that the power regulation is done through modulating a square wave rather than controlling a DC output. If that is the case then coax might be "required" as not emit any RF interference.
2) or the coax could simply be a nice cable with suitable electrical, mechanical and aesthetic properties...

"M-gineering" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

BobT said:

I am making plans to install lights on my new touring bike and connect
them to a Schmidt hub dynamo.

In researching this, I note that the Schmidt lights are supplied with
"heavy duty coaxial cable" to connect to the dynamo. Why would shielded
coaxial cable be needed to connect up a hub dynamo and lights?

It is strong, wearresistant, easy to route and elegant. That it happens to
be coaxial (which is more work to nstall) is something you have to take
with the advantages

--
---
Marten Gerritsen

INFOapestaartjeM-GINEERINGpuntNL
www.m-gineering.nl

Thank you for your response here and also for the useful information on your
web site about lighting.

To summarize: The coaxial cable is selected by Schmidt because of its
mechanical/physical characteristics rather than any need for the electrical
shielding properties of coaxial cable.

BobT

In article <[email hidden]>,

BobT said:

"Tim McNamara" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Hmmm. Except you're setting up more than 3W of power consumption-
5.4W or 6.6W. You'll want to check and make sure you'll have
enough juice to run them all- at low speeds in particular.

I've found several descriptions saying this will work - at Peter
White's site:

http://www.peterwhitecycles.com/wiringinstructions.asp

and here:

http://www.m-gineering.nl/son12vg.htm

The Schmidt dynamo functions as a constant current device. You
connect the 2.4 watt primary headlight (B&M Lumotec N Plus in my
case) in parallel with the 0.6 watt tail light (I'm using a B&M
DToplight plus). You then connect the secondary 3 watt headlight
(I'm using a Schimdt E6-z) in series with the other lights. With
this setup, the dynamo produces 12 volts, 6 watts when a speed of
about 10 m.p.h. is reached and powers all three lights
satisfactorily. If riding continually at a slower speed, one
switches off the secondary light because I'm told that one fully
powered light is brighter than two under powered lights.

I hadn't thought of that combination, but it should work. The caveat is
that you won't be able to use the second light effectively at low
speeds- but then at low speeds the need for lots of headlight is much
lower so it's not a big deal.

Quoted message said:

Back to the wire question: I assume (often a mistake) that in this
sophisticated, German engineered dynamo / light system, if coaxial
cable is used it must be for some good reason, but what reason?

My hunch is that it mainly just looks better. It's a little less
convenient to work with.

dabac said:

BobT said:

Back to the wire question: I assume (often a mistake) that in this
sophisticated, German engineered dynamo / light system, if coaxial
cable is
used it must be for some good reason, but what reason?

BobT

I haven't looked at the schematics so this is merely speculation:

1) one reason could be that the power regulation is done through
modulating a square wave rather than controlling a DC output. If that
is the case then coax might be "required" as not emit any RF
interference.

Bike generators put out AC, not DC. It's a sine wave, or pretty close.
And, strictly speaking, it isn't power that's regulated. Current is
regulated, and it's an inherent function of the design. As speed
increases, AC frequency increases. The generator's inherent inductance
works with this increasing frequency to limit output.

I say there is no power regulation because with hub generators or (at
least some) bottom bracket generators, you can get about six watts of
power out by connecting two headlights in series. That's assuming your
speed is not too low. That's what the OP was discussing. If power
were regulated, that wouldn't be possible.

Regarding the original question: I can't imagine any reason the coax
would be mandatory.

And about the wiring and switching, you may want to try this: Instead
of just using a switch to short out one headlamp at low speed, I
eventually installed a single pole, double thow, center off switch
between the headlights, accessible at the handlebars. The "single
pole" terminal goes to the conductor between the two lights. Each
"throw" (output terminal) is used to short out one of the headlights.
(That is, it connects to the generator-side terminal on each
headlight.)

The benefit here is that I can switch either headlight on or off
independently. (I'm using it now to compare bulbs and optics in two
lamps.) Should I blow a bulb (admittedly, very rare) I can just switch
to the other headlight to ride home. And the center position leaves
both lamps in the circuit, for high speed work.

- Frank Krygowski

<[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

And about the wiring and switching, you may want to try this: Instead
of just using a switch to short out one headlamp at low speed, I
eventually installed a single pole, double thow, center off switch
between the headlights, accessible at the handlebars. The "single
pole" terminal goes to the conductor between the two lights. Each
"throw" (output terminal) is used to short out one of the headlights.
(That is, it connects to the generator-side terminal on each
headlight.)

The benefit here is that I can switch either headlight on or off
independently. (I'm using it now to compare bulbs and optics in two
lamps.) Should I blow a bulb (admittedly, very rare) I can just switch
to the other headlight to ride home. And the center position leaves
both lamps in the circuit, for high speed work.

- Frank Krygowski

Does your dynamo also power a tail light and if so, how is connected in the
setup you describe?

BobT

BobT said:

In researching this, I note that the Schmidt lights are supplied with
"heavy duty coaxial cable" to connect to the dynamo. Why would shielded
coaxial cable be needed to connect up a hub dynamo and lights?

Because a single round cable looks better than a twin wireset, and there
are no issues with places where the cable twists and doesn't lie flat.

That's just a guess, mind you, but other than aesthetic, no, no reason.

Quoted message said:

For my application (tail light and two independently switched front lights),
I want to modify the wiring harnesses that come with the lights. I am
wondering if it makes much difference what wire I use in this 6 volt, 3 watt
system?

At half an amp, you don't want to use too small a wire gauge. 22-24 AWG
would probably be good enough. Keep in mind that while the wire to the
rear light isn't doing anything near half an amp, that's closer to 50 mA,
but it is also a much longer run and therefore using the same gauge for
both runs is probably warranted.

Go for the thickest copper over the minimum you can afford slash are
willing to put up with on the bike.

Jasper

BobT said:

<[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

And about the wiring and switching, you may want to try this: Instead
of just using a switch to short out one headlamp at low speed, I
eventually installed a single pole, double thow, center off switch
between the headlights, accessible at the handlebars. The "single
pole" terminal goes to the conductor between the two lights. Each
"throw" (output terminal) is used to short out one of the headlights.
(That is, it connects to the generator-side terminal on each
headlight.)

The benefit here is that I can switch either headlight on or off
independently. (I'm using it now to compare bulbs and optics in two
lamps.) Should I blow a bulb (admittedly, very rare) I can just switch
to the other headlight to ride home. And the center position leaves
both lamps in the circuit, for high speed work.

- Frank Krygowski

Does your dynamo also power a tail light and if so, how is connected in the
setup you describe?

Yes, I've got a taillight, but it's switched. It's in parallel with
the left front lamp, but a SPST switch on my handlebars can turn it
off. (It has to be parallel to just one headlight, else the little 6V,
0.6W bulb would blow.)

I was curious about the relative brightness of an overdriven 2.4 watt
bulb (i.e. with no taillight) versus a 3 watt bulb with no taillight,
hence that setup. I find there is a noticeable rise in the left lamp's
brightness with the taillight shut off, but the 3 watt lamp on the
right seems still brighter.

BTW, I've also got an LED blinkie in back (AA powered) and some pretty
standard reflectors.

Next step, I think, is an LED generator headlamp.

- Frank Krygowski

Mon, 27 Nov 2006 09:02:00 +0100, M-gineering:

Quoted message said:

It is strong, wearresistant, easy to route and elegant. That it happens
to be coaxial (which is more work to nstall) is something you have to
take with the advantages

There is one more advantage: The "shield wire" is the one connected to
electrical ground at the lights. This way, if the outer isolation of the
coaxial wire is damaged, just this grounded wire makes contact with the
bike frame and nothing is shorted out.

Andreas - employee at Schmidt Maschinenbau