From: John Tserkezis 
Reply-To: Fidonet AVtech Echo 

Brenton wrote:

> Don't worry about the consultancy fees.  They won't be that high :)

  You've forgotten to tell him the invoice for the email support is in the mail 
already. :-)

> As you increase the frequency, the efficiency also increases.  This means less
> power lost or dissipated as heat which means smaller coils etc, and longer
> battery life if battery powered.  What John Smith said was partially right about
> Farnell pricing, but it is also a matter of trying to buy just one.  Dick Smith
> / Jaycar, or any of the "hobby" suppliers wont carry any of
the parts we'd be
> looking at, which means relying on someone like Farnell for one-offs.  It's been
> a while since I've bought from them, so I don't know of any minimum order
> charge.

  As I've mentioned in the other message, jaycar has the LM2576 available as 
one-offs, about $14 a pop.  They also have pre-wound toroidal inductors 
available off the shelf, hopefully the right one for your application.

  Efficiency might be an issue, I'm using one on 5v equipment at about an amp 
(or just over actually), the heatsink is 5cmx5cm thinnish aluminium plate 
mounted within the case.
  It gets warm if it's been on for a while, but well within specs.  At 3 amps a 
larger heatsink would be wise.  A larger coil wouldn't go astray either.

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