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Sci.Electronics.Basics -> Help me build a bicycle phone charger

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Author: BikePilgrim
Date: 19:36 07-01-08

Hello, I recently built-up a front wheel for my bicycle that has a 6v/
3.5w dynamo. These are designed to power headlamps, but I'd prefer to
store the electricity in a battery which could charge my phone. I
believe iPhones charge on standard USB.

My first question is about the battery. Of course, any cell or
chemistry would do, but I'd like to use NiMH AA cells so that I could
easily replace them, and use them in other devices like cameras and
radios while I'm bike-camping. From what I've read, charging NiMH
isn't easy, so I'd prefer to find something off the shelf to use. Is
it possible (or advisable) to use a AA charger as a battery while also
charging the cells? I'm quite in the dark on this topic, and would
appreciate any guidance I can get.

Next, once I have a battery pack that's being charged by my front
wheel, how should I go about charging the iPhone. I will likely use an
off-the-shelf iPhone car charger which are often little more than
cigarette lighter to USB adapters, but these are made for 12v, so I
assume their circuits will be mostly useless to me. What would be
involved in creating a USB outlet on my battery pack?

Once those two fundamental questions are answered I'd like to dream a
little; It'd be most awesome to have a loud speaker built into the
battery pack so that the iPhone could also bump tunes when I'm riding
with friends. Assuming I can somehow re-purpose an OTS iPhone dock, I
should have access to some audio wires, and run them to a volume
dimmer and then to a small speaker. A headlight would be handy too,
but I'm not sure that there will be enough juice for all that. Just
wanted to throw that out there so y'all will know where I'm going.

And just to put minds at ease, I'll use a good sturdy protector case
to house it while it's mounted on the bike. I don't want it to get
hurt in an accident, but it'll be handy to have maps available on my
handlebars.

This is my first serious electronics project, so I'm all ears.

Author: Bob Monsen
Date: 23:52 07-01-08

"BikePilgrim" <bikepilgrim@gmail.com> wrote in message
news:0d3c8c2c-2ebd-4d87-9292-2b28db923dd6@i72g2000hsd.googlegroups.com...
> Hello, I recently built-up a front wheel for my bicycle that has a 6v/
> 3.5w dynamo. These are designed to power headlamps, but I'd prefer to
> store the electricity in a battery which could charge my phone. I
> believe iPhones charge on standard USB.
>

USB gives 5V, so you can probably just plug the iPhone in (with the right
cable, of course) to the dynamo itself. The iPhone is almost certainly set
up to handle higher voltages during charging. If you are worried, you can
take your car to iPhone charger, and see if it is regulated down to 5V. You
could also regulate the output of the dynamo down to 5V yourself using a low
dropout 5V regulator.

> My first question is about the battery. Of course, any cell or
> chemistry would do, but I'd like to use NiMH AA cells so that I could
> easily replace them, and use them in other devices like cameras and
> radios while I'm bike-camping. From what I've read, charging NiMH
> isn't easy, so I'd prefer to find something off the shelf to use. Is
> it possible (or advisable) to use a AA charger as a battery while also
> charging the cells? I'm quite in the dark on this topic, and would
> appreciate any guidance I can get.
>

NiMH cells are pretty easy to charge at low current. Just limit the current
to 1/10 of the rating of the battery, and you should be fine. They can
overheat if they get overcharged, leading to shorter life. However, they
won't burst into flames like a LiION pack. However, why not just use the
iPhone itself to handle charge management, by plugging the thing directly
into your dynamo. That way, you can play it while you ride, and it'll charge
when the voltage is high enough.

> Next, once I have a battery pack that's being charged by my front
> wheel, how should I go about charging the iPhone. I will likely use an
> off-the-shelf iPhone car charger which are often little more than
> cigarette lighter to USB adapters, but these are made for 12v, so I
> assume their circuits will be mostly useless to me. What would be
> involved in creating a USB outlet on my battery pack?
>
> Once those two fundamental questions are answered I'd like to dream a
> little; It'd be most awesome to have a loud speaker built into the
> battery pack so that the iPhone could also bump tunes when I'm riding
> with friends. Assuming I can somehow re-purpose an OTS iPhone dock, I
> should have access to some audio wires, and run them to a volume
> dimmer and then to a small speaker. A headlight would be handy too,
> but I'm not sure that there will be enough juice for all that. Just
> wanted to throw that out there so y'all will know where I'm going.
>

You'll need a battery pack for this one. You can buy batteries that fit into
a bottle holder. Here is one:

http://www.eatonbikes.com/detail.aspx?ID=190416&Name=Night+Rover%2C+Water+Bottle+Bat
tery%2C+Light

You can build a nice little amplifier for it using an LM384 or something
like that. Google for LM384 datasheet, and scroll down. There are schematics
for an amp that would work for you. You could probably just tear the OTS
iPhone dock apart to get the speakers and plugs.

> And just to put minds at ease, I'll use a good sturdy protector case
> to house it while it's mounted on the bike. I don't want it to get
> hurt in an accident, but it'll be handy to have maps available on my
> handlebars.
>
> This is my first serious electronics project, so I'm all ears.

Author: Ian Malcolm
Date: 03:21 08-01-08

Bob Monsen wrote:
> "BikePilgrim" <bikepilgrim@gmail.com> wrote in message
> news:0d3c8c2c-2ebd-4d87-9292-2b28db923dd6@i72g2000hsd.googlegroups.com...
>
>> Hello, I recently built-up a front wheel for my bicycle that has a 6v/
>> 3.5w dynamo. These are designed to power headlamps, but I'd prefer to
>> store the electricity in a battery which could charge my phone. I
>> believe iPhones charge on standard USB.
>>
>
> USB gives 5V, so you can probably just plug the iPhone in (with the
> right cable, of course) to the dynamo itself. The iPhone is almost
> certainly set up to handle higher voltages during charging. If you are
> worried, you can take your car to iPhone charger, and see if it is
> regulated down to 5V. You could also regulate the output of the dynamo
> down to 5V yourself using a low dropout 5V regulator.
>
>> My first question is about the battery. Of course, any cell or
>> chemistry would do, but I'd like to use NiMH AA cells so that I could
>> easily replace them, and use them in other devices like cameras and
>> radios while I'm bike-camping. From what I've read, charging NiMH
>> isn't easy, so I'd prefer to find something off the shelf to use. Is
>> it possible (or advisable) to use a AA charger as a battery while also
>> charging the cells? I'm quite in the dark on this topic, and would
>> appreciate any guidance I can get.
>>
>
> NiMH cells are pretty easy to charge at low current. Just limit the
> current to 1/10 of the rating of the battery, and you should be fine.
> They can overheat if they get overcharged, leading to shorter life.
> However, they won't burst into flames like a LiION pack. However, why
> not just use the iPhone itself to handle charge management, by plugging
> the thing directly into your dynamo. That way, you can play it while you
> ride, and it'll charge when the voltage is high enough.
>
>> Next, once I have a battery pack that's being charged by my front
>> wheel, how should I go about charging the iPhone. I will likely use an
>> off-the-shelf iPhone car charger which are often little more than
>> cigarette lighter to USB adapters, but these are made for 12v, so I
>> assume their circuits will be mostly useless to me. What would be
>> involved in creating a USB outlet on my battery pack?
>>
>> Once those two fundamental questions are answered I'd like to dream a
>> little; It'd be most awesome to have a loud speaker built into the
>> battery pack so that the iPhone could also bump tunes when I'm riding
>> with friends. Assuming I can somehow re-purpose an OTS iPhone dock, I
>> should have access to some audio wires, and run them to a volume
>> dimmer and then to a small speaker. A headlight would be handy too,
>> but I'm not sure that there will be enough juice for all that. Just
>> wanted to throw that out there so y'all will know where I'm going.
>>
>
> You'll need a battery pack for this one. You can buy batteries that fit
> into a bottle holder. Here is one:
>
>
http://www.eatonbikes.com/detail.aspx?ID=190416&Name=Night+Rover%2C+Water+Bottle+Batte
ry%2C+Light
>
>
> You can build a nice little amplifier for it using an LM384 or something
> like that. Google for LM384 datasheet, and scroll down. There are
> schematics for an amp that would work for you. You could probably just
> tear the OTS iPhone dock apart to get the speakers and plugs.
>
>> And just to put minds at ease, I'll use a good sturdy protector case
>> to house it while it's mounted on the bike. I don't want it to get
>> hurt in an accident, but it'll be handy to have maps available on my
>> handlebars.
>>
>> This is my first serious electronics project, so I'm all ears.
>
>
Before you do *anything*, flip the bike over and connect the hub
'dynamo' to an appropriate bulb. Make sure there is *no* way the bike
can fall over then spin the wheel fast enough to light the bulb and
using a multimeter on DC volts, check the voltage from the 'dynamo'
then repeat on AC Volts. I strongly suspect that your 'dynamo' is
actually a permanent magnet alternator and outputs AC!

It would also be worth checking the output at the maximum speed you are
likely to do with no load on the 'dynamo' (a bike computer to check the
speed and a drill with a foam sanding drum with no sandpaper on the
outside of it to drive the wheel by pressing it agents the tyre may be
some help here). I wouldn't be surprised to see way over 12V on open
circuit, downhill conditions.

OTOH maybe Bob is trying to do us all a public service by incinerating
your phone on the basis that cyclists operating iPhones while riding
although a self correcting problem from a Practical Darwinist
perspective, is likely to result in considerable expense to the rest of
us in terms of loss of no claims discount and visual clutter consisting
of tacky roadside 'shrines'.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL:

Author: Bob Monsen
Date: 10:16 08-01-08

"Ian Malcolm" <valid.address.in.signature@invalid.invalid> wrote in
message
news:flvbld$p9i$1@inews.gazeta.pl...
> OTOH maybe Bob is trying to do us all a public service by incinerating
> your phone on the basis that cyclists operating iPhones while riding
> although a self correcting problem from a Practical Darwinist perspective,
> is likely to result in considerable expense to the rest of us in terms of
> loss of no claims discount and visual clutter consisting of tacky roadside
> 'shrines'.
>

You've blown my cover! :)

Thanks, I was assuming DC. Sorry to the OP.

Regards,
Bob Monsen

Author: default
Date: 10:53 08-01-08

On Mon, 7 Jan 2008 16:36:00 -0800 (PST), BikePilgrim
<bikepilgrim@gmail.com> wrote:

>Hello, I recently built-up a front wheel for my bicycle that has a 6v/
>3.5w dynamo. These are designed to power headlamps, but I'd prefer to
>store the electricity in a battery which could charge my phone. I
>believe iPhones charge on standard USB.
>
>My first question is about the battery. Of course, any cell or
>chemistry would do, but I'd like to use NiMH AA cells so that I could
>easily replace them, and use them in other devices like cameras and
>radios while I'm bike-camping. From what I've read, charging NiMH
>isn't easy, so I'd prefer to find something off the shelf to use. Is
>it possible (or advisable) to use a AA charger as a battery while also
>charging the cells? I'm quite in the dark on this topic, and would
>appreciate any guidance I can get.
>
>Next, once I have a battery pack that's being charged by my front
>wheel, how should I go about charging the iPhone. I will likely use an
>off-the-shelf iPhone car charger which are often little more than
>cigarette lighter to USB adapters, but these are made for 12v, so I
>assume their circuits will be mostly useless to me. What would be
>involved in creating a USB outlet on my battery pack?
>
>Once those two fundamental questions are answered I'd like to dream a
>little; It'd be most awesome to have a loud speaker built into the
>battery pack so that the iPhone could also bump tunes when I'm riding
>with friends. Assuming I can somehow re-purpose an OTS iPhone dock, I
>should have access to some audio wires, and run them to a volume
>dimmer and then to a small speaker. A headlight would be handy too,
>but I'm not sure that there will be enough juice for all that. Just
>wanted to throw that out there so y'all will know where I'm going.
>
>And just to put minds at ease, I'll use a good sturdy protector case
>to house it while it's mounted on the bike. I don't want it to get
>hurt in an accident, but it'll be handy to have maps available on my
>handlebars.
>
>This is my first serious electronics project, so I'm all ears.

If it were me, I'd start up front with efficiency. Forget the I phone
car charger since the people that make them may not have efficiency at
heart - after all they have an auto to do the peddling and it has a
300+ watt alternator.

Any watts you devote to toys will have to come out of your legs - you
produce maybe 50-70 watts with sweat.

I think I'd charge a NiMH battery since they are cheap and easy to
deal with and don't explode as easily as lithium.

I'd find the OC voltage of the alternator, and charge a cap to its
full voltage then use a high efficiency buck converter to lower the
voltage for battery charging and perhaps even run the headlight from
the battery pack and put an emergency switch to run the light direct
when the battery is discharged.

"Bump tunes when riding with friends?" I wouldn't ride with anyone
who takes their music. Weather radio or walkie talkie, maybe, lights
for the camp, certainly. You could always get a Winnebago.
--

Author: whit3rd
Date: 19:22 08-01-08

On Jan 7, 4:36=A0pm, BikePilgrim <bikepilg...@gmail.com> wrote:
> Hello, I recently built-up a front wheel for my bicycle that has a 6v/
> 3.5w dynamo. These are designed to power headlamps, but I'd prefer to
> store the electricity in a battery which could charge my phone. I
> believe iPhones charge on standard USB.

Well, most bicycle lights are powered from AC (and my dynamo measured
about 15V with 14 ohms output impedance, but that's variable, the
bicycle speed has a major effect). Your iPhone wants 5 Vdc, regulated
(i.e. 4.8 to 5.2V allowable range) and with up to 500 mA required.

So, first you have to convert AC (chassis ground) to DC; then
you need to use that DC to effectively charge a battery. Then you
need to tap regulated power from the battery source (the battery
is a very good filter, much safer to get power after the battery than
upstream straight from the generator).

I did something similar with a voltage doubler rectifier (capacitor/
two
diodes), a lead-acid 6V battery, using the internal impedance of
the dynamo as the only current limit. Then a low-dropout regulator
set at 5.8V actually ran my headlamp. The linear regulator was
a power-wasting component, but it didn't waste much (mainly
just kept the AC peaks out of the vulnerable filament).

You'll want to use a switchable 5V regulator of some sort, so it
doesn't
drain the battery when you aren't docked to the iPod. And you'll
want to verify that the batteries you use (NiMH) can reach 5V
(it'll probably take five or more cells in series). A standard USB
socket (or a pigtail lead with a USB socket) will connect to
the standard iPod cables for charging.

Date: 05:32 10-01-08

On 8 jan, 01:36, BikePilgrim <bikepilg...@gmail.com> wrote:
> Hello, I recently built-up a front wheel for my bicycle that has a 6v/
> 3.5w dynamo. These are designed to power headlamps, but I'd prefer to
> store the electricity in a battery which could charge my phone. I
> believe iPhones charge on standard USB.
>
> My first question is about the battery. Of course, any cell or
> chemistry would do, but I'd like to use NiMH AA cells so that I could
> easily replace them, and use them in other devices like cameras and
> radios while I'm bike-camping. From what I've read, charging NiMH
> isn't easy, so I'd prefer to find something off the shelf to use. Is
> it possible (or advisable) to use a AA charger as a battery while also
> charging the cells? I'm quite in the dark on this topic, and would
> appreciate any guidance I can get.
>
> Next, once I have a battery pack that's being charged by my front
> wheel, how should I go about charging the iPhone. I will likely use an
> off-the-shelf iPhone car charger which are often little more than
> cigarette lighter to USB adapters, but these are made for 12v, so I
> assume their circuits will be mostly useless to me. What would be
> involved in creating a USB outlet on my battery pack?
>
> Once those two fundamental questions are answered I'd like to dream a
> little; It'd be most awesome to have a loud speaker built into the
> battery pack so that the iPhone could also bump tunes when I'm riding
> with friends. Assuming I can somehow re-purpose an OTS iPhone dock, I
> should have access to some audio wires, and run them to a volume
> dimmer and then to a small speaker. A headlight would be handy too,
> but I'm not sure that there will be enough juice for all that. Just
> wanted to throw that out there so y'all will know where I'm going.
>
> And just to put minds at ease, I'll use a good sturdy protector case
> to house it while it's mounted on the bike. I don't want it to get
> hurt in an accident, but it'll be handy to have maps available on my
> handlebars.
>
> This is my first serious electronics project, so I'm all ears.

i'm just going to say you : HAPPY NEW YEAR!
And I whish you do a good research on internet to find that you want.
I must answer to a topic because my electronic teacher ask me to do
it ! And I don't know anything about this topic, consequently i can't
answer !

Date: 17:39 14-02-08

On Jan 8, 3:21 am, Ian Malcolm
<valid.address.in.signat...@invalid.invalid> wrote:
> Bob Monsen wrote:
> > "BikePilgrim" <bikepilg...@gmail.com> wrote in message
> >news:0d3c8c2c-2ebd-4d87-9292-2b28db923dd6@i72g2000hsd.googlegroups.com...
>
> >> Hello, I recently built-up a front wheel for my bicycle that has a 6v/
> >> 3.5w dynamo. These are designed to power headlamps, but I'd prefer to
> >> store the electricity in a battery which could charge my phone. I
> >> believe iPhones charge on standard USB.
>
> > USB gives 5V, so you can probably just plug the iPhone in (with the
> > right cable, of course) to the dynamo itself. The iPhone is almost
> > certainly set up to handle higher voltages during charging. If you are
> > worried, you can take your car to iPhone charger, and see if it is
> > regulated down to 5V. You could also regulate the output of the dynamo
> > down to 5V yourself using a low dropout 5V regulator.
>
> >> My first question is about the battery. Of course, any cell or
> >> chemistry would do, but I'd like to use NiMH AA cells so that I could
> >> easily replace them, and use them in other devices like cameras and
> >> radios while I'm bike-camping. From what I've read, charging NiMH
> >> isn't easy, so I'd prefer to find something off the shelf to use. Is
> >> it possible (or advisable) to use a AA charger as a battery while also
> >> charging the cells? I'm quite in the dark on this topic, and would
> >> appreciate any guidance I can get.
>
> > NiMH cells are pretty easy to charge at low current. Just limit the
> > current to 1/10 of the rating of the battery, and you should be fine.
> > They can overheat if they get overcharged, leading to shorter life.
> > However, they won't burst into flames like a LiION pack. However, why
> > not just use the iPhone itself to handle charge management, by plugging
> > the thing directly into your dynamo. That way, you can play it while you
> > ride, and it'll charge when the voltage is high enough.
>
> >> Next, once I have a battery pack that's being charged by my front
> >> wheel, how should I go about charging the iPhone. I will likely use an
> >> off-the-shelf iPhone car charger which are often little more than
> >> cigarette lighter to USB adapters, but these are made for 12v, so I
> >> assume their circuits will be mostly useless to me. What would be
> >> involved in creating a USB outlet on my battery pack?
>
> >> Once those two fundamental questions are answered I'd like to dream a
> >> little; It'd be most awesome to have a loud speaker built into the
> >> battery pack so that the iPhone could also bump tunes when I'm riding
> >> with friends. Assuming I can somehow re-purpose an OTS iPhone dock, I
> >> should have access to some audio wires, and run them to a volume
> >> dimmer and then to a small speaker. A headlight would be handy too,
> >> but I'm not sure that there will be enough juice for all that. Just
> >> wanted to throw that out there so y'all will know where I'm going.
>
> > You'll need a battery pack for this one. You can buy batteries that fit
> > into a bottle holder. Here is one:
>
> >http://www.eatonbikes.com/detail.aspx?ID=190416&Name=Night+Rover%2C+W...
>
> > You can build a nice little amplifier for it using an LM384 or something
> > like that. Google for LM384 datasheet, and scroll down. There are
> > schematics for an amp that would work for you. You could probably just
> > tear the OTS iPhone dock apart to get the speakers and plugs.
>
> >> And just to put minds at ease, I'll use a good sturdy protector case
> >> to house it while it's mounted on the bike. I don't want it to get
> >> hurt in an accident, but it'll be handy to have maps available on my
> >> handlebars.
>
> >> This is my first serious electronics project, so I'm all ears.
>
> Before you do *anything*, flip the bike over and connect the hub
> 'dynamo' to an appropriate bulb. Make sure there is *no* way the bike
> can fall over then spin the wheel fast enough to light the bulb and
> using a multimeter on DC volts, check the voltage from the 'dynamo'
> then repeat on AC Volts. I strongly suspect that your 'dynamo' is
> actually a permanent magnet alternator and outputs AC!
>
> It would also be worth checking the output at the maximum speed you are
> likely to do with no load on the 'dynamo' (a bike computer to check the
> speed and a drill with a foam sanding drum with no sandpaper on the
> outside of it to drive the wheel by pressing it agents the tyre may be
> some help here). I wouldn't be surprised to see way over 12V on open
> circuit, downhill conditions.
>
> OTOH maybe Bob is trying to do us all a public service by incinerating
> your phone on the basis that cyclists operating iPhones while riding
> although a self correcting problem from a Practical Darwinist
> perspective, is likely to result in considerable expense to the rest of
> us in terms of loss of no claims discount and visual clutter consisting
> of tacky roadside 'shrines'.
>
> --
> Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
> ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
> [at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL:

are you guys saying that it is totally fine to just go ahead and wire
up a usb cable to a 6v3w dynamo and use it to recharge an iphone?
i have been looking into different projects like this and have not
found definitive answer.

thanks in advance

Author: Bob Monsen
Date: 01:13 15-02-08

No, don't do that. The consensus is that your dynamo is probably outputting
AC, which wouldn't be good for the iPod

Instead, use a 7805 voltage regulator, along with a bridge rectifier and a
capacitor, like this:
(view with courier font)
____
| |
.-----------o-------o------|7805|---o-------- iPod Vcc
| | | |____| |
| | | | |
Shottky - Shottky - | | |
^ ^ |+ | |
| _ | === | ---
| / \ | /-\ | ---
o---(~ ~)---o | | |
| \_/ | | 2200uF | | 0.1uF
| | | | |
Shottky - Shottky - | | |
^ ^ | | |
| | | | |
'-----------o-------o--------o------o-------- iPod GND
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

This will limit the input to 5V, and rectify the circuit. The thing in the
middle of the bridge is the output from your dynamo.

The diodes are all pointing up (ie, line is at the top). You could use
Shottky diodes like 1N5817s, or silicon diodes like 1N4001s. The shottky
diodes will waste less power, and let you get more juice out of the thing.
You can also get integrated bridge chips, that have 4 terminals, and
incorporate the 4 diodes. They are generally marked with two terminals that
have a ~ marking, and two that have + and -, respectively. If you get one of
these, hook the dynamo to the ~ terminals, and hook the + to the 7805 input,
and the - to the GND input.

Sorry about the misinformation earlier; I was thinking DC rather than AC.
Please test this circuit with an ohmmeter before you try it on your iPod...

Regards,
Bob Monsen

<mikeinternet@gmail.com> wrote in message
news:a3a3f06b-1b28-49a9-98fd-31fc777de5c8@e25g2000prg.googlegroups.com...
> On Jan 8, 3:21 am, Ian Malcolm
> <valid.address.in.signat...@invalid.invalid> wrote:
>> Bob Monsen wrote:
>> > "BikePilgrim" <bikepilg...@gmail.com> wrote in message
>> >news:0d3c8c2c-2ebd-4d87-9292-2b28db923dd6@i72g2000hsd.googlegroups.com...
>>
>> >> Hello, I recently built-up a front wheel for my bicycle that has a 6v/
>> >> 3.5w dynamo. These are designed to power headlamps, but I'd prefer to
>> >> store the electricity in a battery which could charge my phone. I
>> >> believe iPhones charge on standard USB.
>>
>> > USB gives 5V, so you can probably just plug the iPhone in (with the
>> > right cable, of course) to the dynamo itself. The iPhone is almost
>> > certainly set up to handle higher voltages during charging. If you are
>> > worried, you can take your car to iPhone charger, and see if it is
>> > regulated down to 5V. You could also regulate the output of the dynamo
>> > down to 5V yourself using a low dropout 5V regulator.
>>
>> >> My first question is about the battery. Of course, any cell or
>> >> chemistry would do, but I'd like to use NiMH AA cells so that I could
>> >> easily replace them, and use them in other devices like cameras and
>> >> radios while I'm bike-camping. From what I've read, charging NiMH
>> >> isn't easy, so I'd prefer to find something off the shelf to use. Is
>> >> it possible (or advisable) to use a AA charger as a battery while also
>> >> charging the cells? I'm quite in the dark on this topic, and would
>> >> appreciate any guidance I can get.
>>
>> > NiMH cells are pretty easy to charge at low current. Just limit the
>> > current to 1/10 of the rating of the battery, and you should be fine.
>> > They can overheat if they get overcharged, leading to shorter life.
>> > However, they won't burst into flames like a LiION pack. However, why
>> > not just use the iPhone itself to handle charge management, by plugging
>> > the thing directly into your dynamo. That way, you can play it while
>> > you
>> > ride, and it'll charge when the voltage is high enough.
>>
>> >> Next, once I have a battery pack that's being charged by my front
>> >> wheel, how should I go about charging the iPhone. I will likely use an
>> >> off-the-shelf iPhone car charger which are often little more than
>> >> cigarette lighter to USB adapters, but these are made for 12v, so I
>> >> assume their circuits will be mostly useless to me. What would be
>> >> involved in creating a USB outlet on my battery pack?
>>
>> >> Once those two fundamental questions are answered I'd like to dream a
>> >> little; It'd be most awesome to have a loud speaker built into the
>> >> battery pack so that the iPhone could also bump tunes when I'm riding
>> >> with friends. Assuming I can somehow re-purpose an OTS iPhone dock, I
>> >> should have access to some audio wires, and run them to a volume
>> >> dimmer and then to a small speaker. A headlight would be handy too,
>> >> but I'm not sure that there will be enough juice for all that. Just
>> >> wanted to throw that out there so y'all will know where I'm going.
>>
>> > You'll need a battery pack for this one. You can buy batteries that fit
>> > into a bottle holder. Here is one:
>>
>>
>http://www.eatonbikes.com/detail.aspx?ID=190416&Name=Night+Rover%2C+W...
>>
>> > You can build a nice little amplifier for it using an LM384 or
>> > something
>> > like that. Google for LM384 datasheet, and scroll down. There are
>> > schematics for an amp that would work for you. You could probably just
>> > tear the OTS iPhone dock apart to get the speakers and plugs.
>>
>> >> And just to put minds at ease, I'll use a good sturdy protector case
>> >> to house it while it's mounted on the bike. I don't want it to get
>> >> hurt in an accident, but it'll be handy to have maps available on my
>> >> handlebars.
>>
>> >> This is my first serious electronics project, so I'm all ears.
>>
>> Before you do *anything*, flip the bike over and connect the hub
>> 'dynamo' to an appropriate bulb. Make sure there is *no* way the bike
>> can fall over then spin the wheel fast enough to light the bulb and
>> using a multimeter on DC volts, check the voltage from the 'dynamo'
>> then repeat on AC Volts. I strongly suspect that your 'dynamo' is
>> actually a permanent magnet alternator and outputs AC!
>>
>> It would also be worth checking the output at the maximum speed you are
>> likely to do with no load on the 'dynamo' (a bike computer to check the
>> speed and a drill with a foam sanding drum with no sandpaper on the
>> outside of it to drive the wheel by pressing it agents the tyre may be
>> some help here). I wouldn't be surprised to see way over 12V on open
>> circuit, downhill conditions.
>>
>> OTOH maybe Bob is trying to do us all a public service by incinerating
>> your phone on the basis that cyclists operating iPhones while riding
>> although a self correcting problem from a Practical Darwinist
>> perspective, is likely to result in considerable expense to the rest of
>> us in terms of loss of no claims discount and visual clutter consisting
>> of tacky roadside 'shrines'.
>>
>> --
>> Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
>> ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
>> [at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL:
>
> are you guys saying that it is totally fine to just go ahead and wire
> up a usb cable to a 6v3w dynamo and use it to recharge an iphone?
> i have been looking into different projects like this and have not
> found definitive answer.
>
> thanks in advance

Author: google@woodall.me.uk
Date: 07:40 15-02-08

On Feb 15, 6:13 am, "Bob Monsen" <rcmon...@gmail.com> wrote:
> No, don't do that. The consensus is that your dynamo is probably outputting
> AC, which wouldn't be good for the iPod
>
> Instead, use a 7805 voltage regulator, along with a bridge rectifier and a
> capacitor, like this:
> (view with courier font)
> ____
> | |
> .-----------o-------o------|7805|---o-------- iPod Vcc
> | | | |____| |
> | | | | |
> Shottky - Shottky - | | |
> ^ ^ |+ | |
> | _ | === | ---
> | / \ | /-\ | ---
> o---(~ ~)---o | | |
> | \_/ | | 2200uF | | 0.1uF
> | | | | |
> Shottky - Shottky - | | |
> ^ ^ | | |
> | | | | |
> '-----------o-------o--------o------o-------- iPod GND
> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> This will limit the input to 5V, and rectify the circuit. The thing in the
> middle of the bridge is the output from your dynamo.
>
> The diodes are all pointing up (ie, line is at the top). You could use
> Shottky diodes like 1N5817s, or silicon diodes like 1N4001s. The shottky
> diodes will waste less power, and let you get more juice out of the thing.
> You can also get integrated bridge chips, that have 4 terminals, and
> incorporate the 4 diodes. They are generally marked with two terminals that
> have a ~ marking, and two that have + and -, respectively. If you get one of
> these, hook the dynamo to the ~ terminals, and hook the + to the 7805 input,
> and the - to the GND input.
>
> Sorry about the misinformation earlier; I was thinking DC rather than AC.
> Please test this circuit with an ohmmeter before you try it on your iPod...
>
> Regards,
> Bob Monsen
>
> <mikeinter...@gmail.com> wrote in message
>

The hub dynamos are AC and they're constant current sources, not
constant voltage sources.

They will easily deliver 12V RMS at more than about 10kph. The only
reason they cannot legally be used to drive a 12V 6W light on a
bicycle is that there is a minimum speed that the light has to be up
to full brightness. (And I think 6W is too bright for the main light
on a bicycle in the UK which is (or used to be) limited to a maximum
of 3W to prevent dazzling of other road users)

You probably don't want to use a voltage regulator because you'll be
having to output the full 6W or so of power when cycling once the
battery is fully charged just to heat up the voltage regulator.

I've considered a bridge charging a cap and then a DC-DC converter in
order to get a constant voltage source. If the front light blows it
gets very expensive as that often means the end of the front
standlight and rear light. Currently I'm using two zeners to clamp the
voltage to about 9V (based on 6V RMS having a P-P voltage of about 9V
but even with that I've destroyed a front standlight (but the rear
light survived) when the front bulb went.

Tim.

Author: Bob Monsen
Date: 20:34 16-02-08

<google@woodall.me.uk> wrote in message
news:b55dde06-f1e1-476f-9854-e2ea36cb36ea@e23g2000prf.googlegroups.com...
> On Feb 15, 6:13 am, "Bob Monsen" <rcmon...@gmail.com> wrote:
>> No, don't do that. The consensus is that your dynamo is probably
>> outputting
>> AC, which wouldn't be good for the iPod
>>
>> Instead, use a 7805 voltage regulator, along with a bridge rectifier and
>> a
>> capacitor, like this:
>> (view with courier font)
>> ____
>> | |
>> .-----------o-------o------|7805|---o-------- iPod Vcc
>> | | | |____| |
>> | | | | |
>> Shottky - Shottky - | | |
>> ^ ^ |+ | |
>> | _ | === | ---
>> | / \ | /-\ | ---
>> o---(~ ~)---o | | |
>> | \_/ | | 2200uF | | 0.1uF
>> | | | | |
>> Shottky - Shottky - | | |
>> ^ ^ | | |
>> | | | | |
>> '-----------o-------o--------o------o-------- iPod GND
>> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>>
>> This will limit the input to 5V, and rectify the circuit. The thing in
>> the
>> middle of the bridge is the output from your dynamo.
>>
>> The diodes are all pointing up (ie, line is at the top). You could use
>> Shottky diodes like 1N5817s, or silicon diodes like 1N4001s. The shottky
>> diodes will waste less power, and let you get more juice out of the
>> thing.
>> You can also get integrated bridge chips, that have 4 terminals, and
>> incorporate the 4 diodes. They are generally marked with two terminals
>> that
>> have a ~ marking, and two that have + and -, respectively. If you get one
>> of
>> these, hook the dynamo to the ~ terminals, and hook the + to the 7805
>> input,
>> and the - to the GND input.
>>
>> Sorry about the misinformation earlier; I was thinking DC rather than AC.
>> Please test this circuit with an ohmmeter before you try it on your
>> iPod...
>>
>> Regards,
>> Bob Monsen
>>
>> <mikeinter...@gmail.com> wrote in message
>>
>
> The hub dynamos are AC and they're constant current sources, not
> constant voltage sources.
>
> They will easily deliver 12V RMS at more than about 10kph. The only
> reason they cannot legally be used to drive a 12V 6W light on a
> bicycle is that there is a minimum speed that the light has to be up
> to full brightness. (And I think 6W is too bright for the main light
> on a bicycle in the UK which is (or used to be) limited to a maximum
> of 3W to prevent dazzling of other road users)
>
> You probably don't want to use a voltage regulator because you'll be
> having to output the full 6W or so of power when cycling once the
> battery is fully charged just to heat up the voltage regulator.

Actually, no, this won't happen, because the regulator will simply cut off
the current drawn from the dynamo when the battery is charged (ie, the iPod
no longer draws any current.) So, it'll get easier, not harder.

>
> I've considered a bridge charging a cap and then a DC-DC converter in
> order to get a constant voltage source. If the front light blows it
> gets very expensive as that often means the end of the front
> standlight and rear light. Currently I'm using two zeners to clamp the
> voltage to about 9V (based on 6V RMS having a P-P voltage of about 9V
> but even with that I've destroyed a front standlight (but the rear
> light survived) when the front bulb went.
>
> Tim.

If you do what you suggest here, then the diodes will conduct to ground
whenever the voltage gets above 9V. The diodes will be taking a beating. A
DC-DC converter makes much more sense here. You could also use the linear
regular circuit above with an LM7809 and a couple of 9V DC bulbs.

An LM7805 will accept inputs up to about 30V. If you use a bridge, like the
simple circuit above, and the input is 12VAC RMS, then the max voltage it'll
see is 12 * sqrt(2) = about 17V, minus the diode drops, which depend on what
diodes are used. The linear regulator and capacitor form a buffer which will
protect your bulbs from transient spikes in voltage (up to 30V).

Regarding the iPod, after looking at the apple site, they appear to charge
the batteries using a fast charge scheme, requiring 1A initially. I'm not
sure how this works with USB, which is only supposed to allow 500mA maximum.

So, with a linear regulator, the iPod will charge at 1A at 12V RMS, meaning
it'll suck 12W or more out of the OPs legs when charging. Also, it means
that the linear regulator will dissipate about 7W, which will get it quite
hot unless it is well ventilated (lots of opportunity for that on a bike, I
guess!)

On the other hand, a DC DC converter will let him charge his ipod while
supplying only about about 6W, i.e., 1/2 the muscle power. Now, since you
say that one only gets 12VAC when going over 10kph, it may not be an issue.
Not sure.

The main tradeoff is whether the 6W at high speed is worth learning about
and debugging a DC-DC converter.

Regards,
Bob Monsen

Author: google@woodall.me.uk
Date: 04:11 18-02-08

On Feb 17, 1:34 am, "Bob Monsen" <rcmon...@gmail.com> wrote:
> <goo...@woodall.me.uk> wrote in message
>
> > The hub dynamos are AC and they're constant current sources, not
> > constant voltage sources.
>
> > They will easily deliver 12V RMS at more than about 10kph. The only
> > reason they cannot legally be used to drive a 12V 6W light on a
> > bicycle is that there is a minimum speed that the light has to be up
> > to full brightness. (And I think 6W is too bright for the main light
> > on a bicycle in the UK which is (or used to be) limited to a maximum
> > of 3W to prevent dazzling of other road users)
>
> > You probably don't want to use a voltage regulator because you'll be
> > having to output the full 6W or so of power when cycling once the
> > battery is fully charged just to heat up the voltage regulator.
>
> Actually, no, this won't happen, because the regulator will simply cut off
> the current drawn from the dynamo when the battery is charged (ie, the iPod
> no longer draws any current.) So, it'll get easier, not harder.
>
>
>
> > I've considered a bridge charging a cap and then a DC-DC converter in
> > order to get a constant voltage source. If the front light blows it
> > gets very expensive as that often means the end of the front
> > standlight and rear light. Currently I'm using two zeners to clamp the
> > voltage to about 9V (based on 6V RMS having a P-P voltage of about 9V
> > but even with that I've destroyed a front standlight (but the rear
> > light survived) when the front bulb went.
>
> > Tim.
>
> If you do what you suggest here, then the diodes will conduct to ground
> whenever the voltage gets above 9V. The diodes will be taking a beating. A
> DC-DC converter makes much more sense here. You could also use the linear
> regular circuit above with an LM7809 and a couple of 9V DC bulbs.
>
The diodes shouldn't be conducting anything in normal usage. I've got
a 2W4 bulb and a 0W6 rear light being driven from a 500mA constant
current source. So I should be getting 6V RMS and I should just be
under the (approx) 9V zener clamp.
(Actually I'm using a 3W front bulb because the 2W4 bulbs blow much
too quickly)

The problem is when the front bulb fails. The hub still want to supply
500mA and so the voltage shoots right up. Unsurprisingly, the bulb
tends to go when you're doing 50kph and, on streetlit roads it can be
easy to miss the light going anyway. At around 80GBP to replace the
front and rear lights I don't really care about hammering the zeners
occasionally ;-)

> An LM7805 will accept inputs up to about 30V. If you use a bridge, like the
> simple circuit above, and the input is 12VAC RMS, then the max voltage it'll
> see is 12 * sqrt(2) = about 17V, minus the diode drops, which depend on what
> diodes are used. The linear regulator and capacitor form a buffer which will
> protect your bulbs from transient spikes in voltage (up to 30V).
>
I don't know how high the voltage will go. But driving 2x 6V 3W lights
in series is something that many cyclists with these hubs do. So 12V
RMS at normal cycling speeds (15-20mph) is easily achievable.
Depending on hills you need to consider the open circuit voltage at
30, 40 or even 50mph if you are going to be connecting something like
an ipod

> Regarding the iPod, after looking at the apple site, they appear to charge
> the batteries using a fast charge scheme, requiring 1A initially. I'm not
> sure how this works with USB, which is only supposed to allow 500mA maximum.
>
> So, with a linear regulator, the iPod will charge at 1A at 12V RMS, meaning
> it'll suck 12W or more out of the OPs legs when charging. Also, it means
No. The hub will only supply 500mA. The voltage may rise to 18 or even
24V RMS open circuit. But if you drive a 12Ohm resistive load then
you'll get 6V RMS. (The frequency also changes with speed so inductive
loads are harder to analyse)

> On the other hand, a DC DC converter will let him charge his ipod while
> supplying only about about 6W, i.e., 1/2 the muscle power. Now, since you
> say that one only gets 12VAC when going over 10kph, it may not be an issue.
> Not sure.
>
If you want 6W at 6V then you've got to use a DC-DC converter (or a
transformer). You'll draw 12V 500mA from the hub and then down convert
to give 6V 1A.

> The main tradeoff is whether the 6W at high speed is worth learning about
> and debugging a DC-DC converter.
>
It's not really high speed. It's just that to be road legal the front
light has to be fully lit at little more than walking pace. If you're
prepared to accept your lights aren't fully lit until you are at a
speed where it's possible to balance without weaving all over the road
then you can get twice the voltage out of them (but no more current)

Tim.

Author: ehsjr
Date: 19:35 18-02-08

google@woodall.me.uk wrote:

<snip>

>
>
>
>>An LM7805 will accept inputs up to about 30V. If you use a bridge, like the
>>simple circuit above, and the input is 12VAC RMS, then the max voltage it'll
>>see is 12 * sqrt(2) = about 17V, minus the diode drops, which depend on what
>>diodes are used. The linear regulator and capacitor form a buffer which will
>>protect your bulbs from transient spikes in voltage (up to 30V).
>>
>
> I don't know how high the voltage will go. But driving 2x 6V 3W lights
> in series is something that many cyclists with these hubs do. So 12V
> RMS at normal cycling speeds (15-20mph) is easily achievable.
> Depending on hills you need to consider the open circuit voltage at
> 30, 40 or even 50mph if you are going to be connecting something like
> an ipod
>

The following may be applicable - or I may have missed
something in the thread.

Rectify, pre-regulate to ~30V with a zener & hefty pass transistor.
Then whatever VR chips to provide the needed outputs. Conceptually:

+---+---+--- ---+---+---[78xx]---
|+ | | \_/ | | |
AC==BRIDGE [C] [R] | [C] | Gnd
|- | | | | |
| | +----+ | +---[78xx]---
| | | | | | |
| | [C] [Zd] | | Gnd
| | | | | |
Gnd -----+---+---+----+----+---+

You could change it a little to make a shunt
pre-regulator if desired.

Feature you can add:
You can use the DC to energize a relay when the DC
exceeds X volts. With the relay de-energized, the lights
can be connected to the dynamo or a battery or disconnected
or whatever. When the DC voltage is high enough, the lights
can be connected to a VR output.

DC + ---+---[Relay]---+
| |
P ---
O<-----------/_\ TL431
T |
| |
Gnd ----+-------------+

Ed

<snip>

Author: google@woodall.me.uk
Date: 09:13 19-02-08

On Feb 19, 12:35 am, ehsjr <eh...@bellatlantic.net> wrote:
> goo...@woodall.me.uk wrote:
>
> <snip>
>
>
>
>
>
> >>An LM7805 will accept inputs up to about 30V. If you use a bridge, like the
> >>simple circuit above, and the input is 12VAC RMS, then the max voltage
it'll
> >>see is 12 * sqrt(2) = about 17V, minus the diode drops, which depend on
what
> >>diodes are used. The linear regulator and capacitor form a buffer which
will
> >>protect your bulbs from transient spikes in voltage (up to 30V).
>
> > I don't know how high the voltage will go. But driving 2x 6V 3W lights
> > in series is something that many cyclists with these hubs do. So 12V
> > RMS at normal cycling speeds (15-20mph) is easily achievable.
> > Depending on hills you need to consider the open circuit voltage at
> > 30, 40 or even 50mph if you are going to be connecting something like
> > an ipod
>
> The following may be applicable - or I may have missed
> something in the thread.
>
> Rectify, pre-regulate to ~30V with a zener & hefty pass transistor.
> Then whatever VR chips to provide the needed outputs. Conceptually:
>
> +---+---+--- ---+---+---[78xx]---
> |+ | | \_/ | | |
> AC==BRIDGE [C] [R] | [C] | Gnd
> |- | | | | |
> | | +----+ | +---[78xx]---
> | | | | | | |
> | | [C] [Zd] | | Gnd
> | | | | | |
> Gnd -----+---+---+----+----+---+
>
> You could change it a little to make a shunt
> pre-regulator if desired.
>
> Feature you can add:
> You can use the DC to energize a relay when the DC
> exceeds X volts. With the relay de-energized, the lights
> can be connected to the dynamo or a battery or disconnected
> or whatever. When the DC voltage is high enough, the lights
> can be connected to a VR output.
>
> DC + ---+---[Relay]---+
> | |
> P ---
> O<-----------/_\ TL431
> T |
> | |
> Gnd ----+-------------+
>
> Ed
>
> <snip>

You probably won't get 30V from the hub if you're trying to draw the
full 500mA.

Unfortunately I don't know what you will get and it's hard to measure.
Ideally I'd like to strap an oscilloscope onto the handlebars and then
ride up and down the road trying different (resistive) loads but I
don't have a portable oscilloscope. Another thing I've considered is
using two (upside down) bikes, taking the rear tyre off one and the
front tyre off the dynamo wheel and then putting a belt between them
so that I can try to drive the dynamo at a constant speed using the
pedals of the other bike. Maybe a project for a nice summers day.

The power drawn from the hub is 500mA at whatever voltage is necessary
to drive 500mA through the load (but with some peak voltage that I've
never tried to measure but is definitely in excess of 12V RMS at
normal cycling speeds)

That power comes directly from your pedalling and slows you down which
means you want it to be as low as possible. (The efficiency might
change with the power drawn - again I have no data)

If there is no current drawn at all from the dynamo then there is
(effectively) no drag

Some graphs here:
http://www.nabendynamo.de/english.htm
I'd guess that the "Generator Drag" one is based on a 6V-3W load

There is also some graphs here:
www.nabendynamo.de/12vinfo.htm" target=_blank>http://www.baldurdash.org/OtherStuff/www.nabendynamo.de/12vinfo.htm

Here's what I'm looking for:

1. 100% efficiency :-)
2. zero weight.
3. 6V voltage clamped output that will be "on" at lower voltages if
that is all that is available at the source (I'd accept it turning on
at 6V if the next output (below) is still on at lower speeds)
4. Second low current (50mA?) 3V output with a largish capacitor so it
can continue to provide output for a couple of minutes after stopping.
(This isn't critical because there are lights that already provide a
standlight facility)
5. third 6V regulated output that only becomes live once the first
output is delivering 6V and even if the third output is short
circuited will not drag down the first outputs voltage. (I don't care
if a short circuit of output 1 drags the third output down but the
system must be able to withstand shorts like this)
6. The whole thing robust against severe vibration.
7. Ability to withstand all the outputs going open circuit while the
input is being driven by the hub at at least 30mph for an arbitrarily
long time. I'd guess, but I don't know, that the hubs voltage is
probably clamped at no more than 50V p-p for safety reasons
8. (not critical) Some sort of LED status output that alerts if any
output goes open circuit.

If you can supply that lot then I think the OP's original iPod charger
becomes a fairly trivial exercise.

Tim.

Author: Bob Monsen
Date: 13:23 19-02-08

<google@woodall.me.uk> wrote in message
news:a7b9dce4-f962-48f1-99b7-e09445552398@n75g2000hsh.googlegroups.com...
> On Feb 19, 12:35 am, ehsjr <eh...@bellatlantic.net> wrote:
>> goo...@woodall.me.uk wrote:
>>
>> <snip>
>>
>>
>>
>>
>>
>> >>An LM7805 will accept inputs up to about 30V. If you use a bridge, like

>> >>the
>> >>simple circuit above, and the input is 12VAC RMS, then the max voltage
>> >>it'll
>> >>see is 12 * sqrt(2) = about 17V, minus the diode drops, which depend on

>> >>what
>> >>diodes are used. The linear regulator and capacitor form a buffer which

>> >>will
>> >>protect your bulbs from transient spikes in voltage (up to 30V).
>>
>> > I don't know how high the voltage will go. But driving 2x 6V 3W lights
>> > in series is something that many cyclists with these hubs do. So 12V
>> > RMS at normal cycling speeds (15-20mph) is easily achievable.
>> > Depending on hills you need to consider the open circuit voltage at
>> > 30, 40 or even 50mph if you are going to be connecting something like
>> > an ipod
>>
>> The following may be applicable - or I may have missed
>> something in the thread.
>>
>> Rectify, pre-regulate to ~30V with a zener & hefty pass transistor.
>> Then whatever VR chips to provide the needed outputs. Conceptually:
>>
>> +---+---+--- ---+---+---[78xx]---
>> |+ | | \_/ | | |
>> AC==BRIDGE [C] [R] | [C] | Gnd
>> |- | | | | |
>> | | +----+ | +---[78xx]---
>> | | | | | | |
>> | | [C] [Zd] | | Gnd
>> | | | | | |
>> Gnd -----+---+---+----+----+---+
>>
>> You could change it a little to make a shunt
>> pre-regulator if desired.
>>
>> Feature you can add:
>> You can use the DC to energize a relay when the DC
>> exceeds X volts. With the relay de-energized, the lights
>> can be connected to the dynamo or a battery or disconnected
>> or whatever. When the DC voltage is high enough, the lights
>> can be connected to a VR output.
>>
>> DC + ---+---[Relay]---+
>> | |
>> P ---
>> O<-----------/_\ TL431
>> T |
>> | |
>> Gnd ----+-------------+
>>
>> Ed
>>
>> <snip>
>
> You probably won't get 30V from the hub if you're trying to draw the
> full 500mA.
>
> Unfortunately I don't know what you will get and it's hard to measure.
> Ideally I'd like to strap an oscilloscope onto the handlebars and then
> ride up and down the road trying different (resistive) loads but I
> don't have a portable oscilloscope. Another thing I've considered is
> using two (upside down) bikes, taking the rear tyre off one and the
> front tyre off the dynamo wheel and then putting a belt between them
> so that I can try to drive the dynamo at a constant speed using the
> pedals of the other bike. Maybe a project for a nice summers day.
>
> The power drawn from the hub is 500mA at whatever voltage is necessary
> to drive 500mA through the load (but with some peak voltage that I've
> never tried to measure but is definitely in excess of 12V RMS at
> normal cycling speeds)
>
> That power comes directly from your pedalling and slows you down which
> means you want it to be as low as possible. (The efficiency might
> change with the power drawn - again I have no data)
>
> If there is no current drawn at all from the dynamo then there is
> (effectively) no drag
>
> Some graphs here:
> http://www.nabendynamo.de/english.htm
> I'd guess that the "Generator Drag" one is based on a 6V-3W load
>
> There is also some graphs here:
> www.nabendynamo.de/12vinfo.htm" target=_blank>http://www.baldurdash.org/OtherStuff/www.nabendynamo.de/12vinfo.htm
>
> Here's what I'm looking for:
>
> 1. 100% efficiency :-)
> 2. zero weight.
> 3. 6V voltage clamped output that will be "on" at lower voltages if
> that is all that is available at the source (I'd accept it turning on
> at 6V if the next output (below) is still on at lower speeds)
> 4. Second low current (50mA?) 3V output with a largish capacitor so it
> can continue to provide output for a couple of minutes after stopping.
> (This isn't critical because there are lights that already provide a
> standlight facility)
> 5. third 6V regulated output that only becomes live once the first
> output is delivering 6V and even if the third output is short
> circuited will not drag down the first outputs voltage. (I don't care
> if a short circuit of output 1 drags the third output down but the
> system must be able to withstand shorts like this)
> 6. The whole thing robust against severe vibration.
> 7. Ability to withstand all the outputs going open circuit while the
> input is being driven by the hub at at least 30mph for an arbitrarily
> long time. I'd guess, but I don't know, that the hubs voltage is
> probably clamped at no more than 50V p-p for safety reasons
> 8. (not critical) Some sort of LED status output that alerts if any
> output goes open circuit.
>
> If you can supply that lot then I think the OP's original iPod charger
> becomes a fairly trivial exercise.
>
> Tim.

Not really all that hard, I think:

____
| |
.------o----o----o------|7805|---o-------- iPod Vcc
| | | | |____| |
| | | | | |
| | | | | |
+-+----' z | |+ | |
A A 24V A | === | ---
IN1 -+ | | | /-\ | ---
IN2 -(-+ LED? | | | |
A A | | | 2200uF | | 0.1uF
+-+----. | |/ | | |
| '--|NPN | | |
| |> | | |
| | | | |
'-----------o----o--------o------o-------- iPod GND

Use a Power NPN Transistor with Heat Sink

(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

Or, you can use the relay circuit above to cut off the input (not nice at
night, I think)

For 100% efficiency, you need the alien technology from Roswell... or those
new carbon sheets of thickness 1 molecule...

Instead of the 7805, you could use a DC-DC converter to get slightly better
performance. However, you are mostly going to be toodling around with the
thing at 9V or less, so this will be fine. In fact, a low dropout regulator
might be better.

Regards,
Bob Monsen

Author: google@woodall.me.uk
Date: 14:26 19-02-08

On Feb 19, 6:23 pm, "Bob Monsen" <rcmon...@gmail.com> wrote:
> <goo...@woodall.me.uk> wrote in message
>
> news:a7b9dce4-f962-48f1-99b7-e09445552398@n75g2000hsh.googlegroups.com...
>
>
>
> > On Feb 19, 12:35 am, ehsjr <eh...@bellatlantic.net> wrote:
> >> goo...@woodall.me.uk wrote:
>
> >> <snip>
>
> >> >>An LM7805 will accept inputs up to about 30V. If you use a bridge,
like
> >> >>the
> >> >>simple circuit above, and the input is 12VAC RMS, then the max
voltage
> >> >>it'll
> >> >>see is 12 * sqrt(2) = about 17V, minus the diode drops, which
depend on
> >> >>what
> >> >>diodes are used. The linear regulator and capacitor form a buffer
which
> >> >>will
> >> >>protect your bulbs from transient spikes in voltage (up to 30V).
>
> >> > I don't know how high the voltage will go. But driving 2x 6V 3W
lights
> >> > in series is something that many cyclists with these hubs do. So 12V
> >> > RMS at normal cycling speeds (15-20mph) is easily achievable.
> >> > Depending on hills you need to consider the open circuit voltage at
> >> > 30, 40 or even 50mph if you are going to be connecting something like
> >> > an ipod
>
> >> The following may be applicable - or I may have missed
> >> something in the thread.
>
> >> Rectify, pre-regulate to ~30V with a zener & hefty pass transistor.
> >> Then whatever VR chips to provide the needed outputs. Conceptually:
>
> >> +---+---+--- ---+---+---[78xx]---
> >> |+ | | \_/ | | |
> >> AC==BRIDGE [C] [R] | [C] | Gnd
> >> |- | | | | |
> >> | | +----+ | +---[78xx]---
> >> | | | | | | |
> >> | | [C] [Zd] | | Gnd
> >> | | | | | |
> >> Gnd -----+---+---+----+----+---+
>
> >> You could change it a little to make a shunt
> >> pre-regulator if desired.
>
> >> Feature you can add:
> >> You can use the DC to energize a relay when the DC
> >> exceeds X volts. With the relay de-energized, the lights
> >> can be connected to the dynamo or a battery or disconnected
> >> or whatever. When the DC voltage is high enough, the lights
> >> can be connected to a VR output.
>
> >> DC + ---+---[Relay]---+
> >> | |
> >> P ---
> >> O<-----------/_\ TL431
> >> T |
> >> | |
> >> Gnd ----+-------------+
>
> >> Ed
>
> >> <snip>
>
> > You probably won't get 30V from the hub if you're trying to draw the
> > full 500mA.
>
> > Unfortunately I don't know what you will get and it's hard to measure.
> > Ideally I'd like to strap an oscilloscope onto the handlebars and then
> > ride up and down the road trying different (resistive) loads but I
> > don't have a portable oscilloscope. Another thing I've considered is
> > using two (upside down) bikes, taking the rear tyre off one and the
> > front tyre off the dynamo wheel and then putting a belt between them
> > so that I can try to drive the dynamo at a constant speed using the
> > pedals of the other bike. Maybe a project for a nice summers day.
>
> > The power drawn from the hub is 500mA at whatever voltage is necessary
> > to drive 500mA through the load (but with some peak voltage that I've
> > never tried to measure but is definitely in excess of 12V RMS at
> > normal cycling speeds)
>
> > That power comes directly from your pedalling and slows you down which
> > means you want it to be as low as possible. (The efficiency might
> > change with the power drawn - again I have no data)
>
> > If there is no current drawn at all from the dynamo then there is
> > (effectively) no drag
>
> > Some graphs here:
> >http://www.nabendynamo.de/english.htm
> > I'd guess that the "Generator Drag" one is based on a 6V-3W load
>
> > There is also some graphs here:
> >www.nabendynamo.de/12vinfo.htm" target=_blank>http://www.baldurdash.org/OtherStuff/www.nabendynamo.de/12vinfo.htm
>
> > Here's what I'm looking for:
>
> > 1. 100% efficiency :-)
> > 2. zero weight.
> > 3. 6V voltage clamped output that will be "on" at lower voltages if
> > that is all that is available at the source (I'd accept it turning on
> > at 6V if the next output (below) is still on at lower speeds)
> > 4. Second low current (50mA?) 3V output with a largish capacitor so it
> > can continue to provide output for a couple of minutes after stopping.
> > (This isn't critical because there are lights that already provide a
> > standlight facility)
> > 5. third 6V regulated output that only becomes live once the first
> > output is delivering 6V and even if the third output is short
> > circuited will not drag down the first outputs voltage. (I don't care
> > if a short circuit of output 1 drags the third output down but the
> > system must be able to withstand shorts like this)
> > 6. The whole thing robust against severe vibration.
> > 7. Ability to withstand all the outputs going open circuit while the
> > input is being driven by the hub at at least 30mph for an arbitrarily
> > long time. I'd guess, but I don't know, that the hubs voltage is
> > probably clamped at no more than 50V p-p for safety reasons
> > 8. (not critical) Some sort of LED status output that alerts if any
> > output goes open circuit.
>
> > If you can supply that lot then I think the OP's original iPod charger
> > becomes a fairly trivial exercise.
>
> > Tim.
>
> Not really all that hard, I think:
>
> ____
> | |
> .------o----o----o------|7805|---o-------- iPod Vcc
> | | | | |____| |
> | | | | | |
> | | | | | |
> +-+----' z | |+ | |
> A A 24V A | === | ---
> IN1 -+ | | | /-\ | ---
> IN2 -(-+ LED? | | | |
> A A | | | 2200uF | | 0.1uF
> +-+----. | |/ | | |
> | '--|NPN | | |
> | |> | | |
> | | | | |
> '-----------o----o--------o------o-------- iPod GND
>
> Use a Power NPN Transistor with Heat Sink
>
> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> Or, you can use the relay circuit above to cut off the input (not nice at
> night, I think)
>
> For 100% efficiency, you need the alien technology from Roswell... or those
> new carbon sheets of thickness 1 molecule...
>
> Instead of the 7805, you could use a DC-DC converter to get slightly better
> performance. However, you are mostly going to be toodling around with the
> thing at 9V or less, so this will be fine. In fact, a low dropout regulator
> might be better.
>
> Regards,
> Bob Monsen

If you drive the voltage regulator from a constant current source and
draw the full current from the output then what is the input voltage
of the regulator? Is it just Vout plus the minimum voltage drop of the
regulator or is it higher?

------
500mA>----| 7805 |---+
------ |
| 10R
| |
------------+------+

What happens if the output isn't quite drawing the full input current?
(replace the 10R with 12R)
In this case I'd expect the input voltage to rise as high as the
source will go which means we're going to be wasting a lot of our leg
power in the regulator.

What about if we're trying to draw more current? (Replace 10R with
8R2)

While an overvolt protection circuit for the lights is nice (and I'm
using a couple of zeners to clamp the AC voltage) what I really want
is to be able to draw 6V 3W to drive my lights and additionally, when
available because I'm going faster, another 6V 3W to do something else
with - whether that be drive a second light, charge some batteries
etc.

Tim.

Author: ehsjr
Date: 02:02 20-02-08

google@woodall.me.uk wrote:
> On Feb 19, 12:35 am, ehsjr <eh...@bellatlantic.net> wrote:
>
>>goo...@woodall.me.uk wrote:
>>
>><snip>
>>
>>
>>
>>
>>
>>>>An LM7805 will accept inputs up to about 30V. If you use a bridge, like
the
>>>>simple circuit above, and the input is 12VAC RMS, then the max voltage
it'll
>>>>see is 12 * sqrt(2) = about 17V, minus the diode drops, which depend on
what
>>>>diodes are used. The linear regulator and capacitor form a buffer which
will
>>>>protect your bulbs from transient spikes in voltage (up to 30V).
>>
>>>I don't know how high the voltage will go. But driving 2x 6V 3W lights
>>>in series is something that many cyclists with these hubs do. So 12V
>>>RMS at normal cycling speeds (15-20mph) is easily achievable.
>>>Depending on hills you need to consider the open circuit voltage at
>>>30, 40 or even 50mph if you are going to be connecting something like
>>>an ipod
>>
>>The following may be applicable - or I may have missed
>>something in the thread.
>>
>>Rectify, pre-regulate to ~30V with a zener & hefty pass transistor.
>>Then whatever VR chips to provide the needed outputs. Conceptually:
>>
>> +---+---+--- ---+---+---[78xx]---
>> |+ | | \_/ | | |
>> AC==BRIDGE [C] [R] | [C] | Gnd
>> |- | | | | |
>> | | +----+ | +---[78xx]---
>> | | | | | | |
>> | | [C] [Zd] | | Gnd
>> | | | | | |
>> Gnd -----+---+---+----+----+---+
>>
>>You could change it a little to make a shunt
>>pre-regulator if desired.
>>
>>Feature you can add:
>>You can use the DC to energize a relay when the DC
>>exceeds X volts. With the relay de-energized, the lights
>>can be connected to the dynamo or a battery or disconnected
>>or whatever. When the DC voltage is high enough, the lights
>>can be connected to a VR output.
>>
>> DC + ---+---[Relay]---+
>> | |
>> P ---
>> O<-----------/_\ TL431
>> T |
>> | |
>> Gnd ----+-------------+
>>
>>Ed
>>
>><snip>
>
>
> You probably won't get 30V from the hub if you're trying to draw the
> full 500mA.

That's good. The circuit above essentially conducts from
very low voltage up to about 30 volts DC from the source
to the inputs of the 78xx regulators.

The reason to pre-regulate was to ensure that the regulators'
input voltage was kept to ~30 volts or less.

>
> Unfortunately I don't know what you will get and it's hard to measure.
> Ideally I'd like to strap an oscilloscope onto the handlebars and then
> ride up and down the road trying different (resistive) loads but I
> don't have a portable oscilloscope. Another thing I've considered is
> using two (upside down) bikes, taking the rear tyre off one and the
> front tyre off the dynamo wheel and then putting a belt between them
> so that I can try to drive the dynamo at a constant speed using the
> pedals of the other bike. Maybe a project for a nice summers day.
>
> The power drawn from the hub is 500mA at whatever voltage is necessary
> to drive 500mA through the load (but with some peak voltage that I've
> never tried to measure but is definitely in excess of 12V RMS at
> normal cycling speeds)
>
> That power comes directly from your pedalling and slows you down which
> means you want it to be as low as possible. (The efficiency might
> change with the power drawn - again I have no data)
>
> If there is no current drawn at all from the dynamo then there is
> (effectively) no drag
>
> Some graphs here:
> http://www.nabendynamo.de/english.htm
> I'd guess that the "Generator Drag" one is based on a 6V-3W load
>
> There is also some graphs here:
> www.nabendynamo.de/12vinfo.htm" target=_blank>http://www.baldurdash.org/OtherStuff/www.nabendynamo.de/12vinfo.htm
>
> Here's what I'm looking for:
>
> 1. 100% efficiency :-)
> 2. zero weight.
> 3. 6V voltage clamped output that will be "on" at lower voltages if
> that is all that is available at the source (I'd accept it turning on
> at 6V if the next output (below) is still on at lower speeds)
> 4. Second low current (50mA?) 3V output with a largish capacitor so it
> can continue to provide output for a couple of minutes after stopping.
> (This isn't critical because there are lights that already provide a
> standlight facility)
> 5. third 6V regulated output that only becomes live once the first
> output is delivering 6V and even if the third output is short
> circuited will not drag down the first outputs voltage. (I don't care
> if a short circuit of output 1 drags the third output down but the
> system must be able to withstand shorts like this)
> 6. The whole thing robust against severe vibration.
> 7. Ability to withstand all the outputs going open circuit while the
> input is being driven by the hub at at least 30mph for an arbitrarily
> long time. I'd guess, but I don't know, that the hubs voltage is
> probably clamped at no more than 50V p-p for safety reasons
> 8. (not critical) Some sort of LED status output that alerts if any
> output goes open circuit.
>
> If you can supply that lot then I think the OP's original iPod charger
> becomes a fairly trivial exercise.
>

Don't want much, do you? Let's see, 100% efficiency,
0 weight ... I give up. Those things are available
in the Twlight Zone ... or not. :-)

To play the game, the specs have to be properly stated.
The voltages alone don't suffice, we need to know the
current that will be drawn from your supplies. You
did not say anything about the *second* 6V supply,
you only mentioned a first and third 6V supply. And you
did not specify the current to be drawn from the two
6V supplies. We also need to know what input power
is available, at what speeds.

The best we can do at this point is a pre-regulator feeding
a DC-DC converter or linear regulator. Bob gave you a shunt
pre-regulator (which would benefit from an added dropping
resistor to protect the shunt transistor) which is nice, I
gave you a pass pre-regulator, which would also benefit from
a dropping resistor (since you insist on 500 ma CC) to protect
the diodes and the source. The dropping resistor will waste
power, as will the linear that follows. A wide input range
DC-DC converter would avoid at least some of that waste.

But playing the game of finding a "wide input range" DC-DC
converter without knowing the range is not something many
people want to do. You'll just come back with "what about x" .

So I'm gonna stick with my offering of a pre-regulator
followed by linears, and whatever warts it carries with
it. :-)

Ed

> Tim.

Author: google@woodall.me.uk
Date: 03:32 20-02-08

On Feb 20, 7:02 am, ehsjr <eh...@bellatlantic.net> wrote:
> goo...@woodall.me.uk wrote:
>
>
> Don't want much, do you? Let's see, 100% efficiency,
> 0 weight ... I give up. Those things are available
> in the Twlight Zone ... or not. :-)
>
OK. But assuming I'm understanding the examples given they're likely
to get worse than 40% efficiency for a single 500mA supply.

> To play the game, the specs have to be properly stated.
> The voltages alone don't suffice, we need to know the
> current that will be drawn from your supplies. You
> did not say anything about the *second* 6V supply,
> you only mentioned a first and third 6V supply. And you
> did not specify the current to be drawn from the two
> 6V supplies. We also need to know what input power
> is available, at what speeds.
>
Maybe there's a typo above that I can't see. But the first supply is
to drive the lights (500mA at 6V). The second supply is to drive a
standlight (50mA at 3V). And the third supply is any power left.

> The best we can do at this point is a pre-regulator feeding
> a DC-DC converter or linear regulator. Bob gave you a shunt
> pre-regulator (which would benefit from an added dropping
> resistor to protect the shunt transistor) which is nice, I
> gave you a pass pre-regulator, which would also benefit from
> a dropping resistor (since you insist on 500 ma CC) to protect
> the diodes and the source. The dropping resistor will waste
> power, as will the linear that follows. A wide input range
> DC-DC converter would avoid at least some of that waste.
>
Maybe I don't understand the circuits