Newsgroups: sci.electronics.misc
Subject: Re: Easiest LED indication of rs232 activity?
References: <1069763743.271658@gurney>
"Frode Undseth"  writes:

> Hi all!
> 
> I'm trying to figure out the simplest way of getting a visual indication
> of activity on a rs232 Tx line. I know rs232 is using +-12V for signalling,
> but is it possible to drive a led through a resistor directly between the
> signal line and 0V withouth weakening the rs232 signal too much? 

Yes with suitably high resistance value and sensitive LED you 
can get useful visual indication.

> Has anyone tried this, 

There are many commercial RS-232 gadgets built in this way 
around. Many small boxes that you connect between two RS-232 
connectors and have LEDs to so RS-232 signals just have a set 
of bicolor LEDs and suitable resistors for current limiting inside 
them. I don't have resistance values in hand, but I quess that 
the serial resistors used in those have value of few kilo-ohms. 

> or are there other better, cheap and simple methods I could use?

Nothign comes to my mind that would be simpler and cheaper.

> Any idea is appreciated..
> 
> Thanx for any help!
> 
> Kind regards,
> Frode Undseth
> 
> 

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/