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

[Jason Proctor]

my amateurish solution was to power the opamps suitably. the scaling 
opamp is powered from +/-5v. i put trimmers in appropriate places and 
tested it with input voltages from +15 to -15. seemed to work ok.

although i did forget about the opamp output DC offset Ray includes 
in his scale/bias page.

(i've not blown the micro yet!)


>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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