Re: Another clueless question...

From: Dbowey (dbowey_at_aol.com)
Date: 11/05/04 

Date: 05 Nov 2004 18:22:23 GMT

toa posted:
<< I'm trying to make sense of an RS232 card that I took from an old PC, which
necessitates my understanding of the PC's ISA bus architecture. I'll be
connecting the card to some custom-made circuitry instead of the ISA bus.
Most of what I've learned about it so far seem straightforward, but the one
thing I'd like to get a tip on, is the power supply. In addition to +5V and
Ground, the card requires a +12V input and, worse, a -12V input. What is the
standard way of providing these voltages? All I have so far is a power
supply offering one output tha can be varied continuously from 0 to 30
volts. So, do I actually need 3 power supplies, or what? >> 

--
The standard way of providing the voltages is by using the PCs power supply, or
buy or scrounge a computer power supply.  They have one or more of: 12V, -12V,
and 5V.  These supplies commonly require a minimum load on each output in order
to work correctly.
You should not be surprised at the need for +12V and -12V, as classical "RS232"
require both polarities, where - is mark (1) and + is space (0).
Don

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