Device to reset power...

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Sun Jun 29 14:35:01 2003

> > Can you toggle any line on any port (say one of the handshake lines on
> > the serial port (RTS, DTR) or one of the lines on a parallel port)? If
> > so, you could use it to drive a transistor and then a relay..
>
> This is pretty much the kind of think that I had in mind, I'm sure I could
> build it, I'm just not sure how. At least the Sparc 5 I'm using has two
> serial ports (one is the system console).

Try something like this :




                         +------------------------+--------------o V+
                         | | (To suit relay)
                        --- +------+
                IN4148 ^ |\ |
                        /|\ | \ | Relay coil
                         | | \ |
                         | +------+
                         | |
                         +-------------------------+
                                                   |
                                                 +-+
                     1k |/
     SIgnal o-----/\/\/-----+------+---------| 2N3904
                              | | |\>-+
                             --- / |
      Serial 1N4148 ^ \ 10k |
      Or TTL /|\ / |
      Port | \ |
                              | | |
        Gnd o-----------------+------+-------------+----------- 0V


'Signal' is any line you can turn on/off, such as RTS (or even TxD if you
can send arbitrarily-long breaks). It can either be an RS232 signal, or a
TTL one.

Choose the external PSU to suit the relay coil voltage.

Connect the contacts of the relay to switch whatever you need to swtich.
If possible, switch the low-voltage side of the PSU transformer (if the
unit uses a wall-wart PSU, this is easy!).

-tony
Received on Sun Jun 29 2003 - 14:35:01 BST