12V pulse to serial port

[Mickael]

I need to read a 12v pulse from a serial port, Can I connect that 12V
pulse directly to the serial cable (Receive pin) and get information
from there?

 

[Lord Garth]

I need to read a 12v pulse from a serial port, Can I connect that 12V
pulse directly to the serial cable (Receive pin) and get information
from there?

The input to an RS232 serial port is supposed to swing between +12V
and -12V. A signal between +3 and -3 is undefined.

You can use a 1488 or one of the Maxim ICs to create the correct
bipolar signal from your source.

You can also use a 4050 hex buffer for level shifting. Its inputs can
withstand a 12 volt input when its supply is 5 volts. The output would
then be capable of being read by the parallel port rather than the serial
port.

See here: http://www.chipcatalog.com/TI/CD4050B.htm

 

[Dbowey]

arriane posted:

I need to read a 12v pulse from a serial port, Can I connect that 12V
pulse directly to the serial cable (Receive pin) and get information
from there?

Probably, yes, but.....

The direct connections between two "RS232" equipments with the Send Data of
each connected to the Recive Data of the other is called a "Null Modem."

I am aware of two different "RS232" specs, however.

One, is the RS232 recommended standard (thus the RS prefix), and its interface
is at +and - 12V. This has always been accepted as a Standard.

The other is the ANSI/EIA 232, which IS an industry Standard, and its interface
is at + and - 5V.

I've mixed the two occasionally with trouble free results, but I usually use a
pull-down resistor on the Receive Data pins to drop the voltage a bit.

Don