Dimming a light?

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

Quoted message said:

Could I increase battery run time and bulb life of a rechargeable light
system by dimming when I didn't need full power?

Instead of twin lamps, I might prefer to use a single 20W halogen lamp if
I could dim it (to the equivelant of 5 and/or 12W lamps) at a flick of a
switch. Battery would be 13.2 or 14.4V (if I get a Lumicycle system).
This would save handlebar space (or having to use Space Grips, etc), and
possibly money and weight too.

I know a simple resistor in series wouldn't save battery power.

Actually it will, but yes, it won't be terribly efficient.

(eg you might get 1/2 current, but that would be less than 1/4 of the light,
even before you account for halogens not dimming terribly well)

cheers,
clive

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

Quoted message said:

Actually it will, but yes, it won't be terribly efficient.

(eg you might get 1/2 current, but that would be less than 1/4 of the light,
even before you account for halogens not dimming terribly well)

This is the major problem. Filament lamps tend not to dim very well,
with a marked colour shift as you provide less voltage. Pulsing it at
full whack would work if it had a response time fast enough but... it
doesn't.

If your mechanical skills are good you might be better designing a
bayonet style lamp head with which you could quick change the lamps
(Keeping spares in the back pocket of your jersey).

Or you could change technology and mercilessly overdrive an LED as I
have. ;-)

Jon

Jon Senior said:

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

Quoted message said:

Actually it will, but yes, it won't be terribly efficient.

(eg you might get 1/2 current, but that would be less than 1/4 of
the light, even before you account for halogens not dimming terribly
well)

This is the major problem. Filament lamps tend not to dim very well,
with a marked colour shift as you provide less voltage.

I'm familiar with the colour shift from using bog standard lights with
"ordinary" batteries. That might be ok for me because, for low-speed
cycling, I wouldn't mind poor colour as long as it still lit the road to
some extent. And the dimming might not be so poor as you might be thinking
(?) in the system I'm considering as the bulbs are over-volted in the first
place. Bulbs are 12V, NiMH battery is 13.2V, LI-ON is 14.4V (haven't
decided which to get yet).

Quoted message said:

Pulsing it at
full whack would work if it had a response time fast enough but... it
doesn't.

Can you explain that a little more please. Do you mean the /bulb/ doesn't
have a fast enough response time? Is pulsing out of the question
altogether? No other options?

Quoted message said:

If your mechanical skills are good you might be better designing a
bayonet style lamp head with which you could quick change the lamps
(Keeping spares in the back pocket of your jersey).

I could change the bulbs quickly anyway (with Lumicycle lamps) and I might
indeed do that sometimes. Want I want to do as well is instantly switch to
a brighter setting when the speed picks up. Even for the darkest unlit
lanes, I don't need a very powerful light for hill climbing and pottering
along at crusing speed -- that makes up most of the time for me so I could
save lots of juice -- but I'd love to blast along with a brighter light when
gravity and wind assists.

Seems like a good idea, and I know the Light and Motion Turbo MV has 6W, 10W
and 13W settings with presumably one bulb. How do they do it?
(Unfortunately I don't fancy the product: run time for money is not good
enough).

ps. An issue comes to mind that throws a spanner in the works. I would
want the "low speed" spot of light on the ground to be nearer to me than the
high speed's. So I think I do need twin-lamps unless I have a quick-tilt
mechanism :-(

Quoted message said:

Or you could change technology and mercilessly overdrive an LED as I
have. ;-)

The thought did cross my mind after reading your thread! I look forward to
reading more reports. What about the colour? It looks nice and white in
the pic. Is it blueish in real life? I wouldn't want that for seeing with.
White or yellowish seems more useful to me.

~PB

Clive George said:

Quoted message said:

I know a simple resistor in series wouldn't save battery power.

Actually it will, but yes, it won't be terribly efficient.

Oh good. My instincts were that it would save power but some misinformation
led me to believe otherwise.

Quoted message said:

(eg you might get 1/2 current, but that would be less than 1/4 of the
light, even before you account for halogens not dimming terribly well)

/Might/ still be worth doing sometimes, though (?)

cheers
~PB

Pete Biggs <[email hidden]> wrote:

: Instead of twin lamps, I might prefer to use a single 20W halogen lamp if
: I could dim it (to the equivelant of 5 and/or 12W lamps) at a flick of a
: switch.

Just get either 1x12W or 1x20W and 1x5W. Dimming lights is tricky, and
doesn't usually save enough power to be worth while. Some circuits try
it with pulsing the power ISTR, but it's basically not worth the bother.
IMO

Arthur

--
Arthur Clune PGP/GPG Key: http://www.clune.org/pubkey.txt
"Blogs are neither necessary nor sufficient for evil to triumph.
They're just what we call an enabling technology" - Danny O'Brien

Quoted message said:

Pete Biggs <[email hidden]> wrote:

: Instead of twin lamps, I might prefer to use a single 20W halogen lamp
if
: I could dim it (to the equivelant of 5 and/or 12W lamps) at a flick of
a
: switch.

My Cat-Eye rechargable does this. It is a single halogen bulb with a two
light settings.

Colin

Quoted message said:

Pete Biggs <[email hidden]> wrote:

: Instead of twin lamps, I might prefer to use a single 20W halogen lamp
if
: I could dim it (to the equivelant of 5 and/or 12W lamps) at a flick of
a
: switch.

My Cat-Eye rechargable does this. It is a single halogen bulb with a two
light settings.

Colin

Quoted message said:

Pete Biggs <[email hidden]> wrote:

: Instead of twin lamps, I might prefer to use a single 20W halogen lamp
if
: I could dim it (to the equivelant of 5 and/or 12W lamps) at a flick of
a
: switch.

My Cat-Eye rechargable does this. It is a single halogen bulb with a two
light settings.

Colin

In article <[email hidden]>, p@melonbiggs{remove says...

Quoted message said:

Can you explain that a little more please. Do you mean the /bulb/ doesn't
have a fast enough response time? Is pulsing out of the question
altogether? No other options?

Filament lamps have a warm-up and warm-down time. Whereas an LED is near
instantaneous you do have to wait for the filament to heat up. I have a
feeling (Nothing more) that PWM won't work very well on filament lamps.

I know for certain that putting square waves through a filament is best
avoided, especially as you'll already be shaking it around enough by
attaching it to a bike.

Quoted message said:

The thought did cross my mind after reading your thread! I look forward to
reading more reports. What about the colour? It looks nice and white in
the pic. Is it blueish in real life? I wouldn't want that for seeing with.
White or yellowish seems more useful to me.

It's a very nice white actually. Far closer to the output of a halogen
than you'd credit. Check out Chris's website (www.solidlights.co.uk) for
some comparison photos (I think he uses the 3W version of the Luxeon).

As detailed in the other thread, I took it for a run in some "proper"
darkness last night and it performed brilliantly. That said, I'm
currently running it at about 120% of the maximum rated current so I can
probably expect a painfully short life span. I was considering an
upgrade to the 3W anyway so probably no real loss. ;-)

Jon

"Pete Biggs" <p@melonbiggs{remove fruit}.tc> wrote in message
news:[email hidden]...

Quoted message said:

Clive George said:

Quoted message said:

I know a simple resistor in series wouldn't save battery power.

Actually it will, but yes, it won't be terribly efficient.

Oh good. My instincts were that it would save power but some

misinformation

Quoted message said:

led me to believe otherwise.

You will need a big resistor - there's a lot of heat to chuck out (or you
could do a switched mode dimmer like Jon's, at which point you merely have
the problem that halogens are much less efficient when undervolted).

Quoted message said:

Quoted message said:

(eg you might get 1/2 current, but that would be less than 1/4 of the
light, even before you account for halogens not dimming terribly well)

/Might/ still be worth doing sometimes, though (?)

Nah. Mr Jones knows about dimming LEDs - that probably works well. There's
no real point with halogens.
I'd go with the 'add another light' option - possibly an LED like Jon's
(except with a bit more current control :-) ).

cheers,
clive

In article said:

In article <[email hidden]>, p@melonbiggs{remove says...

Quoted message said:

Can you explain that a little more please. Do you mean the /bulb/ doesn't
have a fast enough response time? Is pulsing out of the question
altogether? No other options?

Filament lamps have a warm-up and warm-down time. Whereas an LED is near
instantaneous you do have to wait for the filament to heat up. I have a
feeling (Nothing more) that PWM won't work very well on filament lamps.

It works (see Willie Hunt's LVR), but a dimming method it won't work
any better than running it off a lower steady voltage.

Quoted message said:

It's a very nice white actually. Far closer to the output of a halogen
than you'd credit. Check out Chris's website (www.solidlights.co.uk) for
some comparison photos (I think he uses the 3W version of the Luxeon).

He does. I've compared his lights with my halogen, and I think his website
comparison photos give a realistic impression. Very tempting, but not cheap.

Pete Biggs said:

Could I increase battery run time and bulb life of a rechargeable light
system by dimming when I didn't need full power?

Instead of twin lamps, I might prefer to use a single 20W halogen lamp if
I could dim it (to the equivelant of 5 and/or 12W lamps) at a flick of a
switch. Battery would be 13.2 or 14.4V (if I get a Lumicycle system).
This would save handlebar space (or having to use Space Grips, etc), and
possibly money and weight too.

I know a simple resistor in series wouldn't save battery power. How about
pulse width modulation?

Any suggestions for components or a circuit would be mega-appreciated, if
such a project is feasilble at all and not too heavy or expensive (don't
really want to spend more than £20 or £30 on the dimmer).

Please note: I have limited knowledge of electronics but can operate a
soldering iron. Basically, I've messed about with electrics and
electronics a little bit for most of my life but I don't /really/ know
what I'm doing :-)

You could copy this one:
http://www.wenzel.com/pdffiles/dimmer.pdf

Just add an LED lamp and turn off the filament lamp when the halogen is not
needed!

Brian

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

Quoted message said:

Could I increase battery run time and bulb life of a rechargeable light
system by dimming when I didn't need full power?

Instead of twin lamps, I might prefer to use a single 20W halogen lamp if
I could dim it (to the equivelant of 5 and/or 12W lamps) at a flick of a
switch. Battery would be 13.2 or 14.4V (if I get a Lumicycle system).
This would save handlebar space (or having to use Space Grips, etc), and
possibly money and weight too.

I know a simple resistor in series wouldn't save battery power. How about
pulse width modulation?

Any suggestions for components or a circuit would be mega-appreciated, if
such a project is feasilble at all and not too heavy or expensive (don't
really want to spend more than £20 or £30 on the dimmer).

Please note: I have limited knowledge of electronics but can operate a
soldering iron. Basically, I've messed about with electrics and
electronics a little bit for most of my life but I don't /really/ know
what I'm doing :-)

~PB

Brian Drury said:

Just add an LED lamp and turn off the filament lamp when the halogen
is not needed!

I have already got a little Smart Polaris--which I intend to keep on the
bike if poss for low-speed urban use--but it's almost useless at
illuminating unlit roads. Something like Jon's eventually might do the
trick, though.

I don't want a bigger/heavier battery-LED lamp in addition to a rechargeable
system and don't fancy any of the combined LED/halogen jobs on the market
that I've seen--the spec is just not as good as Lumicycle's.

~PB

Jon Senior said:

Filament lamps have a warm-up and warm-down time. Whereas an LED is
near instantaneous you do have to wait for the filament to heat up. I
have a feeling (Nothing more) that PWM won't work very well on
filament lamps.

I know for certain that putting square waves through a filament is
best avoided, especially as you'll already be shaking it around
enough by attaching it to a bike.

Thanks Jon. I'll put the dimming idea on the back back burner for now. In
fact I'll chuck it out the window and think about an LED job instead (to
complement a halogen). I'm not sure about building anything right now but
hopefully will build/buy something like that hopefully in the nearish
future, and run it off a Lumicycle battery.

Keep up the pioneering! 🙂

~PB