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

[Adam Schabtach]

Duh, sorry folks. I just realized that clipping at 5.1V is fine. Don't ask
me how I read "Vcc+0.5V" and came up with a total of 5.05V. I plead guilty
due to the temporary insanity of being self-employed and working and
residing in a household that just adopted two kittens, both of which arrived
with minor operational issues and no service manuals.

--Adam 

> -----Original Message-----
> From: Adam Schabtach [mailto:lists at studionebula.com] 
> Sent: Wednesday, May 20, 2009 1:34 PM
> To: 'synth-diy at dropmix.xs4all.nl'
> Subject: RE: [sdiy] converting a 10v p to p to a 0-5 volt signal
> 
> I've considered that option (and yes, one of the few 
> textbooks I retained from my college years has a selection of 
> relevant circuits), but it's always seemed somewhat more 
> complex than it needs to be. OTOH one quad op-amp and four 
> diodes is obviously not very complex, so I can't really say 
> what I was thinking at the time. Maybe dropping a diode into 
> the feedback loop of the input-scaling circuit would do the 
> trick. (Does the superposition rule apply here?)
> 
> Clipping at 5.1V isn't really good enough, though. The 
> Absolute Maximum Ratings for the ATmega microcontrollers I 
> use specify an upper limit of Vcc+0.5V on any pin.
> 
> --Adam 
> 
> > -----Original Message-----
> > From: David G. Dixon [mailto:dixon at interchange.ubc.ca]
> > Sent: Wednesday, May 20, 2009 12:40 PM
> > To: lists at studionebula.com; synth-diy at dropmix.xs4all.nl
> > Subject: RE: [sdiy] converting a 10v p to p to a 0-5 volt signal
> > 
> > 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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