Re: Audio Amplifiers DIY

["Dave McLaughlin" <dave@xxxxxxx>]

Hi Shane,

Use the MAX232A as it uses smaller value caps.

Use the MAX483 for the RS485 as it is slew rate limited and reduces
noise
and works over longer distances at higher rates.

I have used RS485 interfaces without any termination on subsea umbilicals
of
1500m without any problems but it is best to terminate end last and first
in
the link.

You need to control the TX and RX pins to avoid seeing your own
transmission
etc. I tied the TX and RX enable together and use a line from the PIC
to
select transmit or receive. This gives you half duplex but works well.
You
just need to remember to wait a small turnaorund time before changing
from
TX to RX.

Regards
Dave...
----- Original Message -----
From: "Shane Harrison" <shane.harrison@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Monday, October 21, 2002 9:27 AM
Subject: RE: [ukha_d] Audio Amplifiers DIY


> Hi there,
>
> Well, enough people expressed an interest in the amplifier so I'll
put
> some effort in an put provision for both RS232 and RS485.
>
> Can any one out there supply proven designs that work with PICS or
at
> least answer the following questions:
> 1) RS232 - use MAX232 ?
> 2) RS485 - use MAX481 (half duplex) or MAX491 (full duplex)
> 3) Termination resistors need to be strappable on RS485 ?
> 4) Does the transmitter enable pin on the RS485 drivers need to go
back
> to the PIC (I assume RX enable doesn't) ?
>
> Replying offlist might be more appropriate if it gets a bit
involved.
>
> Cheers and thanks
> Shane

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