[sdiy] converting a 10v p to p to a 0-5 volt signal

David G. Dixon dixon at interchange.ubc.ca
Wed May 20 20:39:30 CEST 2009


To clip to ground without the diode drop, you should use an active
rectifier.  This is basically a diode in the feedback loop of an opamp.  Any
decent book on opamps will have a selection of such circuits with different
attributes (half or full-wave rectification, different input impedances,
virtual ground summing nodes, etc, etc).  I believe that the addition of a
5.1V zener in the loop would clip on the high end.  That may be all you need
to do.  Perhaps one of the gurus could weigh in on this...?
 
> Aside from range scaling, I'm still looking for a good protection circuit
> for microcontroller inputs. I want hard clipping at 0V and 5V to protect
> the
> micro. I've seen various solutions described on this list, but when I put
> them into SPICE I have always found some flaw, such as the lower limit
> actually being one diode-voltage-drop below zero rather than zero. I'd be
> very happy if I could find some nice solution to this problem so that my
> micro-based modules can protect themselves rather than having to depend
> upon
> my poor memory to avoid being subjected to unacceptable voltage ranges. :-
> )
> 
> Or, putting it another way: converting 10Vp-p to 0-5V with op-amps is a
> fine
> solution, but as soon as you add two 10Vp-p signals together (e.g. mixing
> two LFOs) the input range can easily exceed 10Vp-p and hence the output
> range will also exceed 0-5V.
> 
> --Adam
> 
> > -----Original Message-----
> > From: synth-diy-bounces at dropmix.xs4all.nl
> > [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of
> > Jason Proctor
> > Sent: Tuesday, May 19, 2009 6:50 PM
> > To: synth-diy at dropmix.xs4all.nl
> > Subject: Re: [sdiy] converting a 10v p to p to a 0-5 volt signal
> >
> > i did exactly this for my Arduino module. it bidirectionally
> > interfaces a +/-5v signal to the micro's 0-5v range.
> >
> > turned out to be pretty easy - on the way in, chop the signal
> > in half, and bias with +2.5v. then reinvert. on the way out,
> > do the opposite. 1 dual opamp each way.
> >
> > lmk if you want the details.
> >
> > (i should also thank Tom Wiltshire here for his help getting
> > me off the ground with this stuff.)
> >
> >
> > >tonight i was looking at my scope
> > >
> > >Checking the input into a circuit that was only able to take
> > 0-5 volts
> > >
> > >Sure enough, the signal was between 0 and 5 but the sawtooth
> > was clipped.
> > >
> > >So i am looking for a input block that can take either
> > >5vp to p or 10v p to p (or any synth signal)
> > >and spit it out as a 0-5 signal without squaring the top.
> > >
> > >
> > >anyone know of a good circuit for this?
> > >
> > >thanks
> > >
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