Re: OT: Electronics advice needed to make a combined emergency charger / USB supply lead for my PDA

["Mark A Wright" <mawright@xxxxxxxxxxxx>]

Guys thanks for all the advice, I've ordered all the electronic bits now,
I'll let you know how I get on. :-)

Mark
----- Original Message -----
From: Ward, David
To: 'ukha_d@xxxxxxx'
Sent: Thursday, July 15, 2004 9:03 AM
Subject: RE: [ukha_d] OT: Electronics advice needed to make a combined
emergency charger / USB supply lead for my PDA


Maplin stock the 1N5817 which is good for 1A with Vf(max) = 0.5v


-----Original Message-----
From: Frank Mc Alinden [mailto:fmcalind@xxxxxxx]
Sent: 14 July 2004 20:13
To: ukha_d@xxxxxxx
Subject: Re: [ukha_d] OT: Electronics advice needed to make a combined
emergency charger / USB supply lead for my PDA


Hi Mark

> I'm not really sure which diodes to order would a 1N914 Signal Diode
work?

Signal diodes i think are only rated at 100mA......

If you use schottky diodes then the volts drop across is only
200mV.............

HTH
Frank


----- Original Message -----
From: "Mark A Wright" <mawright@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Thursday, July 15, 2004 3:32 AM
Subject: RE: [ukha_d] OT: Electronics advice needed to make a combined
emergency charger / USB supply lead for my PDA


> Thanks for the reply Dave.
>
> I'm not really sure which diodes to order would a 1N914 Signal Diode
work?
>
> The batteries standard charge is 14Hrs at 75mA. So if the supply
voltage
is
> around 5v / 0.075A = 66.6 would a 70 Ohm resistor work to limit the
charging
> side of things? Which resistor would that be R2? Would that not also
limit
> the current from the ni-cads to charge the PDA?
>
> Sorry for asking silly questions :-)
>
> Mark
> ________________________________________
> From: Ward, David [mailto:DAvid.Ward@xxxxxxx]
> Sent: 14 July 2004 17:46
> To: 'ukha_d@xxxxxxx'
> Subject: RE: [ukha_d] OT: Electronics advice needed to make a combined
> emergency charger / USB supply lead for my PDA
>
> just a couple of small changes
>
>
>
> +-------------------[D3]--+
>
>
> ----------+-[D1]-+------------[D2]--+
>
> [R1] [R2]
>
> +5V [LED] [FUSE]
> From
> USB  (+)
>  4x 1.2v (+4.8v) (+)
>  Rechargeable PDA
>  AAA (-)
>  (-)
>
> Common
> ----------+------+------------------+
>
>
>
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