"Dylan Smith" <
[email protected]> wrote in message
news:
[email protected]...
> On 2008-02-22, Nigel Cliffe <[email protected]> wrote:
>>> Otherwise, you're going to need a switch mode regulator which, while
>>> not expensive to build, is a bit more complex (especially if you want
>>> it to regulate as well as a 7805).
>>
>> There are regulator chips around which give the 5.5v for USB from almost
>> any
>> applied voltage. There are numerous internet pages describing how to
>> power
>> an iPod / MP3 player from an AA cell or two.
>
> Yes, these are switch mode. They'll need an inductor and reasonably good
> PCB layout to work properly. Not expensive, but unlike the 7805 which
> will work with the most rudimentary wiring, needs a little more skill to
> assemble and work correctly.
>
> Certainly not beyond an electronics hobbyist, but probably not a newbie
> project, which a rectifier/7805 circuit would be.
>
> --
At the end of the day the company that sells the kit have got it working.
They will sell you it for 2quid.
Having seen a review of it the result is that it does work - but the bottle
dynamo is cheap and ****.
Personally I would want to get my own decent one, I would also want to get
my own handlebar holder (already have a suitable one for my use). The only
thing I need or at least need to see a circuit of is the connector as that
(which the reviewer said was bulky) is where the electronics are held that
would rectify, smooth and regulate the voltage to 12v as you use your own
cig lighter lead that drops the voltage to that which your PDA or phone
needs.
I also understand that a dynamo has a nominal voltage of 6v ac but that is
at around 5mph and voltages of 12+ volts are generally achieved at "normal"
cycling speed of 12mph.
I have just read on an electronics website (I have an interest but am no
expert) that if you feed 6v RMS AC into a bridge rectifier you will loose
1.4v leaving 4.6v RMS DC and this is then increased by the smoothing
capacitor to 6.4v smooth DC.
That being the case if 12v AC is fed into rectifier you end up with 10.6v
RMS which when smoothed will increase to 14.84v DC.
So providing you cig lighter plug can handle from 6 to 15 v then you get
your power. I also understand from the info that if you add a regulator into
the circuit then you will get your constant voltage at the cig soctet before
it is fed to the cig plug.
I would really love to know as I would not really want to spend 20 + quid if
I can do it myself.
Dave
