RE: Audio Amplifiers DIY

["Shane Harrison" <shane.harrison@xxxxxxx>]

Thanks Dave and Frank - That's all clear now thanks.  Appreciate
the
help.

Shane

> -----Original Message-----
> From: Dave McLaughlin [mailto:dave@xxxxxxx] 
> Sent: Monday, 21 October 2002 10:22 p.m.
> To: ukha_d@xxxxxxx
> Subject: Re: [ukha_d] Audio Amplifiers DIY
> 
> 
> 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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