>-----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.
>

The standard RS232 connector has no 5v supply, nor indeed any proper supply
rails.  You can sometimes suck enough current from the signal lines for very
low power operation, but certainly not enough to power any relays.

Regards

Mike




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