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

Jerry Gray-Eskue jerryge at cableone.net
Wed May 20 22:37:51 CEST 2009


<<such as the lower limit
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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