dynamo lighting

[Terry Collins]

Zebee Johnstone wrote:

> Anyone have any experience with dynamos? I know I can go hub or
> bottle, I expect I'll go bottle. Any recommendations?

My preference was for hub over under bracket, over bottle.
Hub (Sturney Archer) was less effort than bottle or under bracket
(between).

Hub is less susceptable to dirt, water (usually) and damage than bottle
or under bracket.

I've had three bottles break down over the first ten years and the Sanyo
under bracket (started to wear), whereas the Sturney Archer hub suffered
loss of magnetisom because I removed the magnet without a keeper(coil of
metal). Woops. I'd hove to see a hub generator with ceramic magnets
these days {

The caveats with hub, bracket, bottle generators are
1) they seem to need 15-20 km/hr to give usuable light,
2) you need to use myriad zener diodes to prevent bulb popping if
zooming downhill,
3) they stop when you stop (some capacitor/battery combo might help
here) and
4) some part has to be left on the bike (usually minimum of generator)
all the time (theft, weather, weight, etc).

OTOH, now it would be interesting to see a system driving good leds
compared to the old incandescent bulb jobs.


In comparison, the issue with batteries systems is cost and weight. The
cheapest is SLA/gel battery which is weighty, but the lightest is led +
Li-On(still most energy dense?), but expensive.

My experience is that all the rechargeable batteries have a life of 2-3
years over which time they degrade capacity and you eventually chuck
them and replace them. So they are great if you are a regular user.

The major problem with rechargeable systems is cheap rechargers. Peeps
leave the batteries plugged in and the recharger recharges them and
slowly starts to overcharge/stew/destroy them.

 

[Terry Collins]

tony f wrote:

> Oh, and of course, I would say...
>
> build your own! (some tips at my site below)

No, no, no. Stay well away from Tony's site. You will end up spending
valuable bicycle funds on lighting project. {.

 

[Terry Collins]

Spiny Norman wrote:

> I can't believe that 50 years later it is not posible to duplicate a
> far more efficient system than that for a bicycle using a generator,

whilst there have been major advances in minaturisation of electronics,
the basic physics of the junction transistor hasn't changed at all, so
any rectification and regulation system tends to rob a few volts off the
system. Given that a lot of hibs and bottles were 6 watts, there wasn't
much to play with.

You see these on battery systems more now as they can give greater
power. You can find a link to one of these on Tony F's site.


> Modern LEDS give out so much light and use so little power that a
> battery of 6 each front and rear should be doddle to power.

6 x 5 Watt is still 30 watt.

 

[Terry Collins]

Euan wrote:

> Easiest way to make sure your lights are safe is to take them with you.
> Given that lights are essential to night time survival I'll happily pay
> ten seconds each time I leave my bike locked up at night. YMMV.

Been there, done that. Definitely wears thin after a while having to
cart around another bag of helmet, pump, and various lights.

 

[Terry Collins]

TimC wrote:

> They're not a lot more efficient -- 2 times at most. What they are is
> a lot less power (unless you're paying for a luxeon). Most worthwhile
> incandescent bulbs are at least 2.4W, whereas people seem perfectly
> content with 0.2W LEDs which barely light up a dark low speed path.

Ooooohhh, petrol chukka {.

We've had this discussion before haven't we.
<wanders of to check his 50 watt incandescent is working okay>

 

[Terry Collins]

Zebee Johnstone wrote:

> 12v seems like I'd have to carry too much battery around.

I believe you are stuck with 6v if you want a hub or bottle generator,
but I gave up 6v for 12v systems as soon as I decided to ditc them.

Alternatively, if you have electonic skills, and faster rider, look at a
voltage doubler circuit to feed the 6v generator into a 12 volt battery.

 

[Terry Collins]

Zebee Johnstone wrote:

> So what would be a good 12v to get? I suppose I just get a smallish
> 12v SLA and wing it?

Jaycar, supercheap Autos, etc, etc, etc sell various sizes in SLA. Feal
the weight, compare the price and try them.

I purchased mine from Jaycar and purchased their little automatic charge
to go with it. It is great for plug in, recharge and forget. Once you
see it flashing, unplug it because it will screw the battery over time.

Okay, with SLAs you have a choice, between seeing batteries as
consumables or carrying weight.

If you want to run a 20W halogen (MR16?) in those cheap automotive
driving light cases you picked up, then, for maximum battery life, you
really need a 18AmpHr SLA battery, if you follow the max discharge of
C/10, i.e 18/10 gives 1.8 amps times 12 volts gives 21(?) watts. But, it
weights 6kg(?)

OTOH, for the price these days and because you don't really want 10
hours lighting, it wouldn't hurt to get a smaller capacity battery and
save on weight, but understand that it s going to fritz in a few months.
One battery per winter?

The other catch with SLAs, discharge isn't linear. if you double the
current out, you get less than half the total
'battery". Read the battery, 18AmpHr capacity is 20 hours discharge time
(fuzz it)

Buy two and a couple of chargers. One at home on charger, use to ride to
work, plug into charger at work, use battery to ride home, then plug
into charger at home. when battery gets cactus/low capacity, move over
to second batter. alternatively take them week about. Resting seems to
help, a little.

 

[Terry Collins]

Zebee Johnstone wrote:

> I expect to be doing 60-90 mins.

Nice commtue.

> Possibly not with both lights all the time, but at least one.

What about tail light?

I carry an 18 AmpHr (yes I know the weight) for an occassional 30 minute
each way commute. Most of the time, it runs a 20W front plus 6 watt
taillight, but coming home for 10 minutes it runs 50watt + 20 watt (lots
of neon advertising lights along busy road). It worked okay for over a
year that I was doing this two night per week and hanging on charger the
rest of the time.

 

[Terry Collins]

flaps wrote:

>
> 12v. Nice and bright. I've been mistaken for a motorcycle

That is nice ins't it. Wife and I are zipping (for us) down a river side
combo path one night and this cop runs out screaming "SLOW DOWN, SLOWN
DOWN", then it is a loud "OH" as he realise it was just two old farts on
bicycles with bright lights {.

 

[Terry Collins]

TimC wrote:

> A factor of two or so for halogen, tungsten is a bit crapper though.
> Not that much. Tis what I am saying. In fact, I'm not even sure of
> that. I am not convinced that a 5W luxeon (LED) is any brighter than
> a 5W halogen. I reckon they are *fainter*!

It might be a different light distribution. I seem toremember reading
this as an explantion in a incandescent light review yonkers. One
particular light had a higher rating for cameras, but looked duller to
the human eye.

Have you loocked at them through a movie camera or other infra red
sensitive camera?
>
> I'd love to put flourescent lights on my bike, but as Zebee mentioned
> once, you'd need big optics.

Optics?. Naah, just a hummungous battery and inverter. Haven't you ever
seen those camping flourescents that run of the Dolphin touch battery?
They also sold them a "shed" lights.

 

[Zebee Johnstone]

In aus.bicycle on Sun, 12 Mar 2006 14:27:15 +1100
Terry Collins <[email protected]> wrote:
> Euan wrote:
>
>> Easiest way to make sure your lights are safe is to take them with you.
>> Given that lights are essential to night time survival I'll happily pay
>> ten seconds each time I leave my bike locked up at night. YMMV.
>
> Been there, done that. Definitely wears thin after a while having to
> cart around another bag of helmet, pump, and various lights.

Yeah. I have a bag that hangs off the seatback, I'm thinking of a
small lockable plastic box on the rack that has the battery (for the
homebrew lights I'm in the middle of making so I have an idea of what
the various wattages etc do) and the tools. THe lights will be
hoseclamped on, the wheels and seat have the 5 sided key skewers.
Sure, a well equipped thief will have no trouble but I'm banking on
the bike not being where such an one will a) see it and b) have time
to pinch bits. Plus I hope the bits won't be that desirable, no idea
who would want skinny 26" and 20" wheels except another bent bod for
example.

Zebee

 

[Zebee Johnstone]

In aus.bicycle on Sun, 12 Mar 2006 14:56:48 +1100
Terry Collins <[email protected]> wrote:
>
>> Possibly not with both lights all the time, but at least one.
>
> What about tail light?

I'm going to stick with the LED flashers and rechargeable AAAs.

Zebee

 

[TimC]

On 2006-03-12, Terry Collins (aka Bruce)
was almost, but not quite, entirely unlike tea:
> TimC wrote:
>> I'd love to put flourescent lights on my bike, but as Zebee mentioned
>> once, you'd need big optics.
>
> Optics?. Naah, just a hummungous battery and inverter. Haven't you ever
> seen those camping flourescents that run of the Dolphin touch battery?
> They also sold them a "shed" lights.

Optics, because they have low surface brightness: 5 times more light
(for a given power input) comes out of an area that's about
3*10*4=120cm^2, compared to LEDs and halogens which are less than
1cm^2. So you need big optics to focus that into a usefully small
beam.

Inverters can be made tiny (I have seen a compact flouro that runs off
12v -- the inverter is in the bayonet housing. Batteries can be 5
times smaller than batteries for halogens, for a given power output.

--
TimC
Smash head on keyboard to continue.

 

[Euan]

Terry Collins wrote:
> Euan wrote:
>
>
>>Easiest way to make sure your lights are safe is to take them with you.
>> Given that lights are essential to night time survival I'll happily pay
>>ten seconds each time I leave my bike locked up at night. YMMV.
>
>
> Been there, done that. Definitely wears thin after a while having to
> cart around another bag of helmet, pump, and various lights.

So how do you secure your pump?
--
Cheers | ~~ [email protected]
Euan | ~~ _-\<,
Melbourne, Australia | ~ (*)/ (*)

 

[TimC]

On 2006-03-12, Terry Collins (aka Bruce)
was almost, but not quite, entirely unlike tea:
> The caveats with hub, bracket, bottle generators are
> 1) they seem to need 15-20 km/hr to give usuable light,
> 2) you need to use myriad zener diodes to prevent bulb popping if
> zooming downhill,

And 2) is crazy talk. I donut understand why dynohubs are still
manufactured with such crazy old school technology.

Zener regulator circuits are so inefficient (for reference, they can
be built for less than $0.40). They simply suck up enough current
until the voltage after the resistor drops below the zener cutoff
voltage. Hell, a simple 3 pin voltage regulator would be more
efficient (although you lose a volt or two across them, although, low
voltage drop regulators exist, and cost less than $5). They at least
don't suck up arbitrary amounts of current -- they simply suck as much
current as the load is drawing.

But you can build switchmode regulators for less than $10 (and
wholesale prices are going to be a heck of a lot below that). Solid
state, no transformers, and simply take as much current as is needed
to satisfy I=P/V (I is current, P is power the light wants, and V is
the voltage input to the light). Wind a few more turns onto the
generator, so that you have enough voltage so the voltage drop across
the regulator doesn't cause you to get voltage dips at the output, and
if paranoid, wire in a zener and fuse to make sure the generator
doesn't generate more than the limiting input voltage of 40V typical
of a switchmode circuit. Such a circuit would almost always have
enough output voltage to satisfy the lights even at very low speeds
(dunno about enough power), would have constant light, and would be
very efficient. Remember that any inefficiencies suck up energy from
the wheel, and ultimately your legs.

But unfortunately, the consumerist society that we live in means that
people don't seem to be willing to pay an extra $10 premium on their
$150 dynohubs for the better quality circuitry. Just witness the
difficulty of buying bike light and battery setups with proper
chargers instead of constant voltage el-cheapo wallwarts (yes, I am
looking at *you*, niteflux visionstick).

> The major problem with rechargeable systems is cheap rechargers. Peeps
> leave the batteries plugged in and the recharger recharges them and
> slowly starts to overcharge/stew/destroy them.

See above rant. It should not add more than at the very most, $10
onto a $250 lighting system (again, I am looking at *you*, niteflux).

--
TimC
Experiments must be reproducible; they should all fail in the same way.

 

[TimC]

On 2006-03-12, Terry Collins (aka Bruce)
was almost, but not quite, entirely unlike tea:
> Spiny Norman wrote:
>
>> I can't believe that 50 years later it is not posible to duplicate a
>> far more efficient system than that for a bicycle using a generator,
>
> whilst there have been major advances in minaturisation of electronics,
> the basic physics of the junction transistor hasn't changed at all, so
> any rectification and regulation system tends to rob a few volts off the
> system.

Have you come across the rectification circuit using mosfets? Seems
to present itself as just a resistor in one direction (of resistance
0.1 ohms, so a win for currents less than 6 amps).

I haven't actually built this circuit, and worked out its limitations,
but I don't see why it wouldn't work:

http://www.geofex.com/Article_Folders/mosswitch/mosswitch.htm
(hmmm, I once saw a better description of operation in an electronics
mag somewhere)

See also the more complicated:
http://www.solarbotics.net/library/circuits/misc_switching.html

--
TimC
When some other esteemed editor reposts this, it'll be the Periodic
Periodic Table Table story, and I will be even happier. ;^)
-- Emil Brink on /., about the periodic table table.

 

[Humbug]

On 12/03/06 at 14:22:22 Terry Collins somehow managed to type:

This isn't directed at Terry but there have been so many untruths and
misconceptions bandied around in this thread it's a joke. You have made
one whoopsie though... You do NOT need a voltage doubler to run a
12V globe from a normal dynamo - either hub, bottle or bottom bracket
mounted, you need a 12V 6W globe. You can duplicate that by connecting
two headlight bulbs in series.

My ancient Union dynamo produces around 60V with only the metering load
at 20kph. It produces its maximum POWER at a tad over 16V at 20kph -
maximum current at 16V is about 520mA. With a load that limits the
voltage to 6V it can only produce nearly 510mA.

To use a 12V battery with a normal dynamo (any type) just put a bridge
rectifier between the dynamo and the battery and use two normal
headlighs connected in series. Crude but effective and cheap.

For more info than you can shake a stick at have a look at the
BikeCurrent mailing list archives at
http://lists.topica.com/lists/bikecurrent/read


And for Tim. There are really only two practical ways to generate
electricity on a bike. Chemically (batteries) or by swinging a magnetic
field through a coil. That's why we still use such ancient devices as
dynamos.

--
Humbug
BE A LOOF! (There has been a recent population explosion of lerts.)

 

[TimC]

On 2006-03-12, Terry Collins (aka Bruce)
was almost, but not quite, entirely unlike tea:
> Jaycar, supercheap Autos, etc, etc, etc sell various sizes in SLA. Feal
> the weight, compare the price and try them.
>
> I purchased mine from Jaycar and purchased their little automatic charge
> to go with it. It is great for plug in, recharge and forget. Once you
> see it flashing, unplug it because it will screw the battery over time.

Gah! As I was ranting before, if it's smart enough to flash a LED, it
is trivial to turn off a freaking mosfet! Narrrrgh!

--
TimC
"COGITO, EGGO SUM." I think, therefore I am a waffle.
.sig of Mr. Ska on Slashdot.org

 

[TimC]

On 2006-03-12, Humbug (aka Bruce)
was almost, but not quite, entirely unlike tea:
> And for Tim. There are really only two practical ways to generate
> electricity on a bike. Chemically (batteries) or by swinging a magnetic
> field through a coil. That's why we still use such ancient devices as
> dynamos.

You misinterpreted. I was objecting to still using zener diodes for
regulation when much better more efficient voltage
regulation/rectification exists.

--
TimC
Computer screens simply ooze buckets of yang.
To balance this, place some women around the corners of the room.
-- Kaz Cooke, Dumb Feng Shui

 

[Random Data]

On Sat, 11 Mar 2006 11:07:52 +0000, Zebee Johnstone wrote:

> I expect to be doing 60-90 mins. Possibly not with both lights all the
> time, but at least one.

At 10W you'd **** that in on a 4Ah gell cell. I used to run close to 2.5
hours off mine.

> Take a fair few NiMH wouldn't it?

You can get them cheap. Last time I bought 12 4.5Ah Cs it cost me around
$70. That's lighter and better capacity than a 4Ah gell cell for around
double the price. You'd also get away with 12 2.2Ah AAs.

Using 12 is pushing the envelope a little, but I've found AAs tend to sag
a bit under load, so 11 gives 12V. Going to 12 shouldn't hurt. With the Cs
you'd get away with 10 cells.

--
Dave Hughes | [email protected]
"Verbogeny is one of the pleasurettes of a creatific thinkerizer."
- Peter da Silva