>Gavin Jackson <vulcan@IHUG.CO.NZ>
> Hi there once again
>
> Correct me if I'm wrong, but I though that the 78XX voltage
> regulators can only take 3X the output voltage on their input,
> so the maximum supply that a 7805 can have as its input
> is 15V.
>

 See below...

 > >sounds like a simple 78L05 with some good filtering (make SURE you use
a
> >diode to prevent the boat from sucking all the power from your pic when
the
> >engine starts)
>
> >michael

 Yea, this is the cheapest solution for a boat. The big effeciency of the
24v/5v convertot is not need.

> >>I'm looking for a DC-DC converter that can step 24V down to 5V. It's
for a PIC I have
> >>onboard a boat. It only needs to be able to supply 5mA max and have as
few
> >>external components as possible.
> >>I have a zener, but that's just using too much batter power.

Mix both!!!  Use 78L05 with 10-15v zenner. Put zenner in serial with 78L05
:

                                             ----------------
    +24v -------zenner----------| inp       out|------------------+5v
                     -        +            |_________|
                                                      | 78L05
    -24v ------------------------------------------------------------- -5v


Alex Torres, Kharkov, Ukraine (exUSSR)
altor@chat.ru
2:461/28@FidoNet
http://www.geocities.com/SiliconValley/Lab/6311