typical RS-232 for PC

[balutan]

Copied from wiki about RS-232, "the standard requires the transmitter to use +12V and ?12V, but requires the receiver to distinguish voltages as low as +3V and -3V. Some manufacturers therefore built transmitters that supplied +5V and -5V and labeled them as "RS-232 compatible."

At what voltage rail does the RS-232 on PC transmit (typically)?

 

[MikeHalloran]

Actual IBM-PC used +/-12, but you can't rely on a generic PC to do that, because many, many of them didn't.

Also; the nature of your question suggests that you intend to steal some current from the RS-232 interface. Get the idea out of your head; many of them will barely light a small LED, much less power receivers and logic in your box.





Mike Halloran
Pembroke Pines, FL, USA

 

[itsmoked]

It's all over the map as it depends on lots of things.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[MacGyverS2000]

Assume the PC meets minimum specs (+/-3V) and be done with it. Thinking otherwise is just a guess and will come back to bite you in the rear when you least expect it.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[zzzjim]

Plenty of newer PCs and laptops no longer have the voltage to run 5V logic from RAW Handshaking lines .
10 years ago these sat at +/- 7 to 9 volts

RS-232 Tx-Rx ICs even had 232 in their names .

Assuming any better than +/- 3V will work
.. when it feels like it !

( measure actual equipment to be used for clues )

 

[ScottyUK]

Just think about how many modern PCs don't even have an RS-232 port, let alone a full-spec port. You are designing for a rapidly shrinking market. Anyway you can get more power and better speed out of a USB interface, and most computers of today have at least one USB port.



----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[benta]

Scotty, I don't think you'll find ANY computer today without a USB port.

Benta.

 

[IRstuff]

Only if you don't consider the iPad to be a computer...

TTFN

FAQ731-376

 

[MacGyverS2000]

I don't...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[photoengineer]

+/- 5 V

Cedar Bluff Engineering

http://cedarbluffengineering.webs.com

 

[ScottyUK]

Tell that to Allen Bradley's 1747-PIC which drew its power from the port. Damned things were 'usually' ok on a full-spec serial port, and somewhere between temperamental and plain dead on most modern ports. Ironically IBM laptop ports were among the offenders for refusing to work with this device.


----------------------------------

If we learn from our mistakes I'm getting a great education!