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From: "Klaus Vestergaard Kragelund"
Subject: Re: Little help required........
Date: Wed, 16 Oct 2002 10:15:31 -0400
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
Organization: TDC Internet
"Groenewegen" wrote in message
> Hi, im working on a little project of mine and am a bit stuck. Just
> wondering if any one could help.
> I need a circuit which will convert an RS-232 signal into a 0 to 5 volt
> signal (and its logical inverse)
> 1) Only linear devices (op-amps) are being used
> 2) I have an analogue input of 12 to +12 volts
> 3) Output is obviously 0 to 5 volts (inverse as well)
> 4) I am using a TL 072 device
> 5) And only one 15 volt power supply
> 6) Finally I only have one dual op-amp IC to use for all input signal
> conditioning and this IC has to be used with a single power supply.
> Thanks for any help :)
Forget the TL072 and use a comparator instead (LM139 or eq)
Add a pull-up resistor to the output that goes to your +5V supply. Power the
comparator from +/- 12V and use either a resistor divider at the input or
clamping diodes to limit input voltage swing. Also add plenty of hysteresis
to increase signal noise immunity
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