Signals of the RS-232 Port / Belegung der RS232 Schnittstelle:


9 Pin

25 Pin

Designation of Signal

Type

1

8

CD (Carrier Detection)

input

2

3

RxD (Recieve Data)

input

3

2

TxD (Transmit Data)

output

4

20

DTR (Data Terminal Ready)

output

5

7

GND (Ground)

ground

6

6

DSR (Data Set Ready)

input

7

4

RTS (Request To Send)

output

8

5

CTS (Clear to Send)

input

9

22

RI (Ring Indicator)

input




ASCII Schematic of the Hardware / ASCII Schaltplan der Hardware:

I used a relay from RS-components:
Order No. 291-9710 (Price around 2,6 Euro)
The main adavantage for using a relay and not a transistor based circuit is the isolation.

In order to protect your computer from damage I would advise you to use a relay!

According to the technical data's you may find a suitable one, I think it is probably likely that thers is more than one supplier available.
If you use another relay you should check the current consumed by the coil. If this is to high you could damage your Computer.
Pin Assignment of the relay (RS-Components Order No: 291-9710)

          TOP-View

14       13          9      8
|                           |
|______________\____________|
|                           |
|            _____          |
|         __|     |__       |
|        |  |_____|  |      |
|        |           |      |
|        |____|/|____|      |
|        |    |\|    |      |
|        |           |      |
1        2           6      7
         +

         Technical Data:
         DC-Coil 5V (3,7-10 V)
         Max. switch current: 0,5 A
         Max. switch voltage: 100 V
         Max. switch power:   10 W
         Resistance of the Coil: 500 ohm
         Typ. driving time:   0,5 ms




                          PIN No.
          No LED           2____6               
 DTR_______|\|_____________| K1 |____________________ GND
           |/|             |____|
         Type: 1N4001         |
         or equivalent        |
                              |
                              |
                              |
                              |
         ____________________/ _________________ max. 0,5 A / 10 W
                              K1                



                          PIN No.
          No LED           2____6               
 RTS_______|\|_____________| K2 |____________________ GND
           |/|             |____|
         Type: 1N4001         |
         or equivalent        |
                              |
                              |
                              |
                              |
         ____________________/ _________________ max. 0,5 A / 10 W
                              K2




This Page was created by Peter Pfrang. Last modification 2003-12-16.