Dynamo Lights Brightness PROBLEM

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

Quoted message said:

I have a new AXA BASTA standard dynamo light set but it is not as
bright as the old chrome dynamo lights,HOW DO I GET IT BRIGHTER?
Is the dynamo generator less powerful than the old chrome dynamos?
Im using 6v,2.4w bulbs and these bulbs are bright enough on another
chrome dynamo light i have and i dont want to use halogen light bulbs.

http://www.langsettcycles.co.uk/products.php

Bad news : halogen light bulbs are rather better. I've not blown one in
ages - why don't you want to use one?

Your old 'mo could have been overrunning the bulbs, which would make them
brighter.

Use a 3w bulb with no rear lamp too. Or a rear lamp made of 24 LEDs in
parallel, 12 pointing one way, 12 the other (electrically). Put this in
series with the front lamp and 'mo.

cheers,
clive

Gordon said:

I have a new AXA BASTA standard dynamo light set but it is not as
bright as the old chrome dynamo lights,HOW DO I GET IT BRIGHTER?
Is the dynamo generator less powerful than the old chrome dynamos?
Im using 6v,2.4w bulbs and these bulbs are bright enough on another
chrome dynamo light i have and i dont want to use halogen light bulbs.

http://www.langsettcycles.co.uk/products.php

I would guess the reflectors inside the light head are different
between your old dynamo light set and the new light set. Light is
produced by a combination of the bulb, wattage, reflectors, etc. No
way to make it brighter except by replacing the entire light head.
There is a reason the Lumotec light heads sell for $30 and the Schmidt
light heads sell for $100 and others sell for a few dollars.

Thanks for the replies,when i take the rear wire out the front light
goes to full brightness and the same thing happens with the rear
light,the dynamo is new and was working to full brightness but suddenly
the front and rear lights are at half brightness after only being used
10 times,WHATS GONE WRONG?

Quoted message said:

Gordon said:

I have a new AXA BASTA standard dynamo light set but it is not as
bright as the old chrome dynamo lights,HOW DO I GET IT BRIGHTER?
Is the dynamo generator less powerful than the old chrome dynamos?
Im using 6v,2.4w bulbs and these bulbs are bright enough on another
chrome dynamo light i have and i dont want to use halogen light bulbs.

http://www.langsettcycles.co.uk/products.php

I would guess the reflectors inside the light head are different
between your old dynamo light set and the new light set. Light is

produced by a combination of the bulb, wattage, reflectors, etc. No
way to make it brighter except by replacing the entire light head.
There is a reason the Lumotec light heads sell for $30 and the Schmidt
light heads sell for $100 and others sell for a few dollars.

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

Quoted message said:

Thanks for the replies,when i take the rear wire out the front light
goes to full brightness and the same thing happens with the rear
light,the dynamo is new and was working to full brightness but suddenly
the front and rear lights are at half brightness after only being used
10 times,WHATS GONE WRONG?

RE the first bit:

Dynamos are sort of constant current devices. They'll stick 0.5A through
whatever you give them provided you're going fast enough - you can use this
to good effect by putting a switchable second front lamp in series (popular
upgrade for SON owners).

So if you remove the back lamp, the 'mo will be sticking 0.5A through a bulb
designed to take 0.4A. It'll be very bright - and probably blow quite
quickly.
If you remove the front, unless you've got some voltage limiting circuitry,
the rear will blow in very short order (BTDT). TBH it's not worth bothering
with filament rear lamps any more. Either use a battery LED and use a 3W
bulb at the front, or use one of the LED back lamps, or use the one I
described in an earlier post.

Re your lamps suddenly being at half brightness - are the bulbs still as
good as they were? What bulbs do you have front and rear? Are the wires
still making appropriate contact?

(and you never explained what you've got against halogen bulbs..)

cheers,
clive

Obviously some manufacturing defect popped something. Take it back to
the store.

Gordon said:

Thanks for the replies,when i take the rear wire out the front light
goes to full brightness and the same thing happens with the rear
light,the dynamo is new and was working to full brightness but suddenly
the front and rear lights are at half brightness after only being used
10 times,WHATS GONE WRONG?

Quoted message said:

Gordon said:

I have a new AXA BASTA standard dynamo light set but it is not as
bright as the old chrome dynamo lights,HOW DO I GET IT BRIGHTER?
Is the dynamo generator less powerful than the old chrome dynamos?
Im using 6v,2.4w bulbs and these bulbs are bright enough on another
chrome dynamo light i have and i dont want to use halogen light bulbs.

http://www.langsettcycles.co.uk/products.php

I would guess the reflectors inside the light head are different
between your old dynamo light set and the new light set. Light is

produced by a combination of the bulb, wattage, reflectors, etc. No
way to make it brighter except by replacing the entire light head.
There is a reason the Lumotec light heads sell for $30 and the Schmidt
light heads sell for $100 and others sell for a few dollars.

In article <[email hidden]>,

Gordon said:

Thanks for the replies,when i take the rear wire out the front light
goes to full brightness and the same thing happens with the rear
light,the dynamo is new and was working to full brightness but suddenly
the front and rear lights are at half brightness after only being used
10 times,WHATS GONE WRONG?

Stop SHOUTING. Jeez. We can't see the thing for ourselves and tell you
what the problem is.

There aren't that many possibilities. I'd look for loose connections
first, including the ground (earth in the UK) connection. I'd check to
make sure that the dynamo isn't slipping on the tire second. If you're
running a standard .6W rear light, I'd check to make sure that the bulb
is a 2.4W and not a 3W. I'd also be inclined to go with an LED rear
light and use a 3W head lamp bulb. IMHO reducing the amount of wiring
reduces the number of potential problems.

In article <[email hidden]>,

Clive George said:

(and you never explained what you've got against halogen bulbs..)

The odds are rather good that he's using a halogen head lamp bulb, since
it's a new dynamo set. Perhaps he meant that he doesn't want to go to
LED "bulbs."

Tim McNamara said:

In article <[email hidden]>,

Gordon said:

Thanks for the replies,when i take the rear wire out the front light
goes to full brightness and the same thing happens with the rear
light,the dynamo is new and was working to full brightness but suddenly
the front and rear lights are at half brightness after only being used
10 times,WHATS GONE WRONG?

Stop SHOUTING. Jeez. We can't see the thing for ourselves and tell you
what the problem is.

There aren't that many possibilities. I'd look for loose connections
first, including the ground (earth in the UK) connection. I'd check to
make sure that the dynamo isn't slipping on the tire second. If you're
running a standard .6W rear light, I'd check to make sure that the bulb
is a 2.4W and not a 3W. I'd also be inclined to go with an LED rear
light and use a 3W head lamp bulb. IMHO reducing the amount of wiring
reduces the number of potential problems.

I thought I was one of the last bastions of filament rear lights when I
changed a month or two ago. I'm amazed people still use them. The LED
rears are bloody good these days and a lot now have the 'standlight[tm]'
function which is worth its weight on gold(about 5g for the weight weenies).

However, when it fscks up, which the last one did (which is why I went
filament) it's a new light time. <shrugs>

<snip>>> There aren't that many possibilities. I'd look for loose
connections

Quoted message said:

Quoted message said:

first, including the ground (earth in the UK) connection. I'd check to
make sure that the dynamo isn't slipping on the tire second. If you're
running a standard .6W rear light, I'd check to make sure that the bulb
is a 2.4W and not a 3W. I'd also be inclined to go with an LED rear
light and use a 3W head lamp bulb. IMHO reducing the amount of wiring
reduces the number of potential problems.

I thought I was one of the last bastions of filament rear lights when I
changed a month or two ago. I'm amazed people still use them. The LED
rears are bloody good these days and a lot now have the 'standlight[tm]'
function which is worth its weight on gold(about 5g for the weight
weenies).

However, when it fscks up, which the last one did (which is why I went
filament) it's a new light time. <shrugs>

Thinking about it, isn't the dynamo actually an alternator? Rotating
magnet, stator coil? In which case one could probably correct the power
factor with a judiciously selected capacitor and do wonders for the output.
Or am I imagining it all?

John

In message <[email hidden]>, dated Thu, 10 Aug
2006, John Nice <johnDOTniceATbtinternetDOTcom@?.?.invalid> writes

Quoted message said:

Thinking about it, isn't the dynamo actually an alternator? Rotating
magnet, stator coil?

Yes.

Quoted message said:

In which case one could probably correct the power factor with a
judiciously selected capacitor and do wonders for the output. Or am I
imagining it all?

No, but correcting the power factor demagnetizes the magnet fairly
quickly.
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

John Nice said:

Thinking about it, isn't the dynamo actually an alternator? Rotating
magnet, stator coil? In which case one could probably correct the power
factor with a judiciously selected capacitor and do wonders for the output.
Or am I imagining it all?

It is an AC device, with a surprisingly high frequency. Yes, you can
correct the power factor, but based on my trials, it produces only a
modest power increase, it's effective only at a certain range of road
speeds (since frequency varies with road speed), it doesn't help
efficiency, and perhaps it will complicate the matching of bulb to
generator.

I actually did measurements of the effects, but - sorry - the data's
about 3000 miles away right now. But what I saw didn't look promising
in a practical sense.

- Frank Krygowski

In rec.bicycles.tech John Nice johnDOTniceATbtinternetDOTcom said:

Thinking about it, isn't the dynamo actually an alternator? Rotating
magnet, stator coil? In which case one could probably correct the power
factor with a judiciously selected capacitor and do wonders for the output.
Or am I imagining it all?

Since the load is purely resistive (the bulb) the power factor is always
one: current and voltage are always in phase.

Perhaps you're thinking of trying to tune a resonant circuit to get
more output? I think that could work in principle, a series capacitor
could be tuned for a low-frequency resonance to extend the output as
the bike slows down. In practice the resistance of the alternator is
so high as to defeat the effect. It would be a little bit like adding
a tuned port to a woofer, to extend the bass response.

I've considered the idea, but it sounds like Fred already tried it and
found it wanting.

bob prohaska

In article <[email hidden]>, "John Nice"
<johnDOTniceATbtinternetDOTcom> says...

Quoted message said:

<snip>>> There aren't that many possibilities. I'd look for loose
connections

Quoted message said:

Quoted message said:

first, including the ground (earth in the UK) connection. I'd check to
make sure that the dynamo isn't slipping on the tire second. If you're
running a standard .6W rear light, I'd check to make sure that the bulb
is a 2.4W and not a 3W. I'd also be inclined to go with an LED rear
light and use a 3W head lamp bulb. IMHO reducing the amount of wiring
reduces the number of potential problems.

I thought I was one of the last bastions of filament rear lights when I
changed a month or two ago. I'm amazed people still use them. The LED
rears are bloody good these days and a lot now have the 'standlight[tm]'
function which is worth its weight on gold(about 5g for the weight
weenies).

However, when it fscks up, which the last one did (which is why I went
filament) it's a new light time. <shrugs>

Thinking about it, isn't the dynamo actually an alternator? Rotating
magnet, stator coil? In which case one could probably correct the power
factor with a judiciously selected capacitor and do wonders for the output.
Or am I imagining it all?

Yes, you are. A filament is a nearly pure resistance load, so the pf is
already equal to 1.

--
Remove the ns_ from if replying by e-mail (but keep posts in the
newsgroups if possible).

In message <[email hidden]>, dated Thu,
17 Aug 2006, David Kerber <ns_dkerber@ns_ids.net> writes

Quoted message said:

Yes, you are. A filament is a nearly pure resistance load, so the pf
is already equal to 1.

The alternator has internal resistance and inductance. To match its
impedance for maximum power transfer, you need a resistor AND a
capacitor. The capacitor resonates with the inductance, but the
resistances apply heavy damping.

As I indicated a while back, doing this can seriously damage your
permanent magnet.
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

Quoted message said:

Quoted message said:

Gordon said:

I have a new AXA BASTA standard dynamo light set but it is not as
bright as the old chrome dynamo lights,HOW DO I GET IT BRIGHTER?
Is the dynamo generator less powerful than the old chrome
dynamos? Im using 6v,2.4w bulbs and these bulbs are bright enough
on another chrome dynamo light i have and i dont want to use
halogen light bulbs.

http://www.langsettcycles.co.uk/products.php

Gordon said:

Thanks for the replies,when i take the rear wire out the front light
goes to full brightness and the same thing happens with the rear
light,the dynamo is new and was working to full brightness but
suddenly the front and rear lights are at half brightness after only
being used 10 times,WHATS GONE WRONG?

Helpful hint: shouting at the world (using all caps) is not likely to
generate lots of helpful replies. You were probably frustrated at the
time, a sentiment we all understand, but it sounds a bit juvenile.
Enough on that...

If you haven't figured out your problem yet, here are a few tips. First,
check the wiring. I mean the supply *and* return wires. Your setup may
have come with one wire for the high side, using the bicycle frame as a
return. Assuming you've mounted the headlamp to the fork crown and
you're using the frame as the return conductor, the headset is part of
the return path. My limited experience shows that the headset can have
limited conductance. Try to run a dedicated return wire from the
headlamp to the generator and see if that helps.

Second, you say that the light set was bright when it was freshly
installed, but your OP asks:

Quoted message said:

Quoted message said:

Quoted message said:

Is the dynamo generator less powerful than the old chrome
dynamos?

I can't rectify these two statements; they seem contradictory. Can you
explain?

Finally, it's possible that you simply have a broken dynamo. Can you go
back to the place of purchase for help?

--
Dave
dvt at psu dot edu

Everyone confesses that exertion which brings out all the powers of body
and mind is the best thing for us; but most people do all they can to
get rid of it, and as a general rule nobody does much more than
circumstances drive them to do. -Harriet Beecher Stowe, abolitionist and
novelist (1811-1896)

In article <[email hidden]>, [email hidden]
says...

Quoted message said:

In message <[email hidden]>, dated Thu,
17 Aug 2006, David Kerber <ns_dkerber@ns_ids.net> writes

Quoted message said:

Yes, you are. A filament is a nearly pure resistance load, so the pf
is already equal to 1.

The alternator has internal resistance and inductance. To match its
impedance for maximum power transfer, you need a resistor AND a
capacitor. The capacitor resonates with the inductance, but the
resistances apply heavy damping.

My power engineering courses were a long time ago, but I don't believe
you can increase the power transfer into a resistive load (the filament)
by adding a capacitance to a circuit; the cap just acts as an
*additional* load (even though it's reactive load).

Having said that, any idea how much inductance? Given the size of the
coils, I would think it's pretty low, but have never measured it.
However, I suppose if the filament had enough twists, it could have a
measurable inductance, and in that case a few pf of capacitance might
help a little.

Quoted message said:

As I indicated a while back, doing this can seriously damage your
permanent magnet.

--
Remove the ns_ from if replying by e-mail (but keep posts in the
newsgroups if possible).

In message <[email hidden]>, dated Fri,
1 Sep 2006, David Kerber <ns_dkerber@ns_ids.net> writes

Quoted message said:

My power engineering courses were a long time ago, but I don't believe
you can increase the power transfer into a resistive load (the
filament) by adding a capacitance to a circuit; the cap just acts as an
*additional* load (even though it's reactive load).

The dynamo is an inductive source, so putting a capacitor IN SERIES with
the load makes a series resonant circuit, eliminating the inductive
reactance.

Quoted message said:

Having said that, any idea how much inductance? Given the size of the
coils, I would think it's pretty low, but have never measured it.
However, I suppose if the filament had enough twists, it could have a
measurable inductance, and in that case a few pf of capacitance might
help a little.

I suggest you think about that again. If the inductance is very small,
you need a very .... capacitor. But the inductance of the lamp is
utterly negligible.
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

David Kerber said:

In article <[email hidden]>, [email hidden]
says...

Quoted message said:

In message <[email hidden]>, dated Thu,
17 Aug 2006, David Kerber <ns_dkerber@ns_ids.net> writes

Quoted message said:

Yes, you are. A filament is a nearly pure resistance load, so the pf
is already equal to 1.

The alternator has internal resistance and inductance. To match its
impedance for maximum power transfer, you need a resistor AND a
capacitor. The capacitor resonates with the inductance, but the
resistances apply heavy damping.

My power engineering courses were a long time ago, but I don't believe
you can increase the power transfer into a resistive load (the filament)
by adding a capacitance to a circuit; the cap just acts as an
*additional* load (even though it's reactive load).

Well, I tried it a few years ago. IANA Electrical Engineer but I had
one helping me.

We tested three different generators and found similar results with
all. Here's some data for a Soubitez bottom-bracket generator. I'll
just give the values for 14 mph, 12 ohm load (i.e. standard generator
headlight bulb), with and without some capacitance. The capacitance
was chosen to give max power boost at about 12 mph, IIRC, and was 100
microFarads. (What's the ASCII abbreviation for "micro"? I'll go with
"mu".)

RMS Voltage: With 100 muF: 7.3 V
without: 6.4 V

Current: With 100 muF: 0.6 A
without: 0.53 A

Power: With 100 muF: 4.4 W
without: 3.4 W

Efficiency: With 100 muF: 42%
without: 39%

The efficiency figures are the least reliable, BTW. Our method of
measuring did not take into account the losses resulting from the
interface between the rubber tire and the generator roller surface, and
those can be considerable.

I'll also note, the September 1995 issue of "Electronics World +
Wireless World" (a British magazine) has a letter to the editor, plus
response, on p. 770 that deals with this issue. For their own reasons,
they used a resistance of 24 Ohms instead of 12 Ohms, with and without
a 50 microFarad capacitor. Above 10 mph, they got more power with the
capacitor than without. A graph on that page shows their results.

So you can get more out of a bike generator by adding capacitance. But
it's not much more, it varies quite a bit with speed, and we judged it
not worth the trouble.

- Frank Krygowski

In message <[email hidden]>,
dated Fri, 1 Sep 2006, [email hidden] writes

Quoted message said:

What's the ASCII abbreviation for "micro"? I'll go with "mu".)

Quoted message said:

'u'. but 'mu' is understood.

You DID put the capacitor in SERIES, didn't you?
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK