Re: [aclug-L] Info Request

[Jeremy S Johnstone <jsjohnst@xxxxxxxxxxx>]

You dont need anything that expensive (not saying that the chip is that
expensize). All you need is a 5 cent NPN transistor and a couple relays.
If someone wants a paticular device built just say so and I'll be glad to
help with schematics.


On Wed, 16 Sep 1998, Steven Saner wrote:

> On Wed, Sep 16, 1998 at 02:44:24PM -0500, John Goerzen wrote:
> > Jeremy S Johnstone <jsjohnst@xxxxxxxxxxx> writes:
> > 
> > > NONNONON.... do not put +/- 5 Volts to the serial port
> > > 
> > > Use a transistor to raise the logically states up / down. If anyone needs
> > > schematics just say so.
> > 
> > Well I wasn't saying one should send voltage to the port, I was saying 
> > to read from the port, as I've read of people hooking up simple on/off 
> > switches this way.  Or was what I said about reading from the port
> > wrong as well?  It's been a long time since I've dealt with them at
> > such a level so I defer to your knowledge on this.
> > 
> > 
> 
> This is more electronics than Linux, but since someone else started it...
> 
> The RS-232 standard is +5 to +15 volts for output logic 1 and -5 to
> -15 volts for output logic 0. Input voltages are +/- 3 to 15 volts
> respectively. I would use a chip that is designed to convert the
> RS-232 signal to standard TTL logic levels such as the Motorola MC1488 and
> MC1489 or equivalent. It makes the interfacing easier.
> 
> 
> -- 
> ==================================================================
> Steven Saner                            SouthWind Internet Access, Inc.
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> 
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