Hi, and welcome.

What you describe is fairly simple, and a PIC is ideally suited to it.

You'll definitely need a programmer, and may I suggest the Wisp628 from
www.voti.nl - it's very economical and works very well.

You need to choose a PIC, and then get started with some simple ciruits. Get
some breadboard for prototyping. Read piclist.com - it's a mine of
information. You'll want to blink an LED to start with, things like the
serial port are not a good idea for your first circuit. But don't be
discouraged. When I started with pics I was successfully using the serial
port within 2 or 3 days.

Don't mess around with low pin count pics, or obsolete ones like the 16F84.
Get yourself a 16F877. Don't be intimidated by it's 40 pins- you won't need
them all. But it's a great microcontroller, that is reasonably future-proof
for the hobbyist, and it's not expensive either.

Someone else will tell you where to get your parts- but I'd guess digikey is
a good start.


A couple of comments on your proposal though:-

- a PIC will not interface directly with a PC RS232 port. You need some kind
of level convertor - like a MAX 232. Trying to opto-isolate the serial port
will make everything complicated. It's not necessary. If you use the Maxim
stock circuit for your Rs-232 interface, and double check your connections,
you'll be fine & won't blow up your port

- it's pretty unlikely that you'll be able to draw enough power from a
serial port to power the PIC *and* a bunch of relays. Use a 7805 voltage
regulator, and plug almost any of the cheapo transformer power supplies in,
and you'll be laughing.

Good luck!

Jon

> -----Original Message-----
> From: Hari Seldon [mailto:hirose_kalganigawa@HOTMAIL.COM]
> Sent: 20 April 2004 09:26
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [PIC] using serial port connected to PIC to control
> a bunch of relays
>
>
> Hi,
>
> I'm looking to build a simple board. The board will have a
> serial RS232 interface that I'll connect to a PC. The board
> will have a PIC (or perhaps an alternative cheap low pin
> count cpu+mem?) which will then drive a bunch of solid state
> relays. I'm hoping to put optocouplers on the serial txd/rxd
> in order to prevent any unexpected behavior on the board from
> damaging the PC. I'm also hoping to power the PIC using the
> 5V coming from the D-9 RS232 connector.
>
> Before I try to do this myself, has anyone done something
> similar. If so, I'd love to get your feedback/sample
> sketches/schematics/diagrams/etc on attempting to achieve the above.
>
> I'm going to be buying all the equipment needed to do this
> from scratch. All I have right now are 3 pieces of copper
> plated board, soldering iron, ferric etching powder, marker
> pen and other basic stuff. So any advice on where to procure
> relevant parts around Santa Clara, CA would be a great help.
> I guess I'll probably need to buy a PIC programmer as well. I
> welcome any feedback/suggestions/advice.
>
> Thanks,
> Hirose
>
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