[sdiy] 555 timer adsr

[Scott Gravenhorst]

James Dunn <james at 4thharmonic.com> wrote:
>Hi,
>
>I'm currently working on a 555 timer based ADSR, but the output doesn't 
>seem to ever completely reach 0v. I saw this schematic online:
>http://www.uni-bonn.de/~uzs159/vcadsr.png
>
>can someone tell me how I would connect the diode as specified at the 
>output op-amp? I assume a 1n4148 would suffice? The circuit I'm using 
>is slightly different (TL071 on the output) but I'm hoping this might 
>work!
>thanks


I would start with something like this - 10K is a starting point, it may be fine, it
may need to be different.   The diode will subract about 0.7 volt.  The resistor is
there so there is a current path for the diode to turn "on".

ASCIIMATIC:

ADSR OUT    1N914 or 1N4148
   >----------->|-------+--------> output
                        |
                        \
                        / 10K
                        \
                        /
                        \
                        |
                        |
                       ---
                      ///    ground












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