Dave Lag wrote:
> Love the RS232 section and the LED section.

Thanks.

> Whats your target audience-

I think there are several different customer types.  One is guys like me.  I
know I would have used something like this a dozen times already if I had a
few of these in the closet.  It probably wouldn't substitute for the real
customer target circuit most of the time, but occasionally you need a quick
circuit to produce a specific sequence of pulses, measure something, quick
and dirty control something from a PC, be a test interface to the customer
circuit, etc.  The cost of these boards would be low enough that it's a no
brainer to use another board as apposed to wiring what you need on a
protoboard with power supply, RS-232 interface, etc.  In the end, I'd throw
the board in the box for that customer project so it'd be available a year
later when the customer want something changed.  With the protoboard
approach, by that time the protoboard would have gotten re-used, and you'd
have to figure out all over again what the test setup was.  Been there, done
that.

The other target is for hobbyists where the board becomes the project.  The
one off cost will still be cheaper than getting a PC board made, especially
if you really only need one.  I know this is a somewhat tougher sell since
many hobbyists either want to do everything themselves or are willing to
spare no expense to save a few pennies.  Still, there will be some that just
want to get on with their project.  This board allows you to get a simple
PIC circuit up and running with external hardware in an evening, which is
not possible if you've got to send out for board or even etch your own.

> Worried all those power supply parts will
> make it expensive.

Expensive as apposed to what?  You will still need a regulated power supply
somehow.  One way or the other, you're going to pay for a full wave bridge,
caps, and a regulating power supply, whether these are in a wall wart, a
bench supply, or on the board.  The cheapest solution would be a linear
regulator like a 7805.  Let's say pessimistically that the parts cost of the
switcher is $3 more than the 7805 solution parts cost.  On the other hand,
the switcher will run from a wall wart available for $1.70 in single
quantity and is more flexible in its input voltage requirements.  Is it
worth it?  I think for the first type of customer it is, but not sure about
the hobbyist.  What do you think?

> All that power supply and I can't run it at LF voltages?

Good point.  Do you want to run at low voltage to test the circuit or to
save power?  If the latter, this board probably isn't for you.  What about
if I add some jumpers around the 5.5V to 5.0V LDO?  That allows you to
disconnect the PIC power from the LDO output, which allows using your own
5.5V to 3.3V (or whatever) regulator on the prototype section, or you could
replace IC3 with a different voltage.  You can even change R5 and R6 to set
the switcher to a different output voltage.


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