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

Scott Nordlund gsn10 at hotmail.com
Wed May 20 23:37:34 CEST 2009


Keep in mind that this is an 8 bit ADC- you don't have the resolution to limit it to something significantly less than full scale, plus it will throw your quantization off....

Yes the diodes will clip the waveform- this is what you want, assuming you've got an op amp or something in there to scale it as well.

You can't limit the instantaneous amplitude of a real-time input without risking some form of distortion.  You could use some sort of companding circuit, but it's still going to clip on extreme transients, plus it will mess up your scaling for CVs.  

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> From: subjectivity at hotmail.com
> To: jerryge at cableone.net; synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] converting a 10v p to p to a 0-5 volt signal
> Date: Wed, 20 May 2009 21:19:29 +0000
> CC:
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> with this 2 diode method (which everyone recommends) do the diodes end up CLIPPING the waveform?
> one thing i really want to watch out for is changing the shape of the wave
>
> this is why maybe David's method of going 1vptop is a good idea.
>
> however i think i would need some heavier boosting on the way out because when i have tried such a small to PtoP i have gotten nill on the output.
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> ----------------------------------------
>> From: jerryge at cableone.net
>> To: synth-diy at dropmix.xs4all.nl
>> Subject: RE: [sdiy] converting a 10v p to p to a 0-5 volt signal
>> Date: Wed, 20 May 2009 15:37:51 -0500
>>
>>
>> <
>> actually being one diode-voltage-drop below zero rather than zero.>>
>>
>> A good protection technique uses a current limit resistor followed by two
>> diodes one the + voltage the other to the - voltage Followed by a Second
>> current limit resistor. The voltage at the Diodes can run from ~ .6 volts
>> above and below the power rails but the second resistor limits the current
>> so that the on chip input protection can clamp the .6 volts at very low
>> current without being damaged.
>>
>>
>>
>> -----Original Message-----
>> From: synth-diy-bounces at dropmix.xs4all.nl
>> [mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of Adam Schabtach
>> Sent: Wednesday, May 20, 2009 12:57 PM
>> To: synth-diy at dropmix.xs4all.nl
>> Subject: RE: [sdiy] converting a 10v p to p to a 0-5 volt signal
>>
>>
>> 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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