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<DIV dir=ltr align=left><SPAN class=808191205-01012019><FONT color=#0000ff
size=2 face=Arial>Oh yeah, and an extra big Thank You to Darren Shorsky for
some much-needed LM393s!!!!! (which dumb ol' Doc Sketchy forgot include in
his Digikey order)</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=808191205-01012019><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=808191205-01012019><FONT color=#0000ff
size=2 face=Arial>Happy New Year, everyone!!!</FONT></SPAN></DIV><BR>
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<FONT size=2 face=Tahoma><B>From:</B> Darren Shorsky
[mailto:dschnidsky@hotmail.com] <BR><B>Sent:</B> Monday, December 31, 2018
7:50 PM<BR><B>To:</B> David G Dixon; 'Oakley Sound'; 'Synth
DIY'<BR><B>Subject:</B> Re: [sdiy] Help, I'm Desperate! (Charge Injection with
DG408)<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV
style="FONT-FAMILY: Calibri, Helvetica, sans-serif; COLOR: rgb(0,0,0); FONT-SIZE: 12pt">Wow
David!!! :O</DIV>
<DIV
style="FONT-FAMILY: Calibri, Helvetica, sans-serif; COLOR: rgb(0,0,0); FONT-SIZE: 12pt"><BR></DIV>
<DIV
style="FONT-FAMILY: Calibri, Helvetica, sans-serif; COLOR: rgb(0,0,0); FONT-SIZE: 12pt">congratulations.....
that sounds like quite the journey.</DIV>
<DIV
style="FONT-FAMILY: Calibri, Helvetica, sans-serif; COLOR: rgb(0,0,0); FONT-SIZE: 12pt"><BR></DIV>
<DIV
style="FONT-FAMILY: Calibri, Helvetica, sans-serif; COLOR: rgb(0,0,0); FONT-SIZE: 12pt">i
look fwd to the video & happy new year.</DIV>
<DIV
style="FONT-FAMILY: Calibri, Helvetica, sans-serif; COLOR: rgb(0,0,0); FONT-SIZE: 12pt"><BR></DIV>
<DIV
style="FONT-FAMILY: Calibri, Helvetica, sans-serif; COLOR: rgb(0,0,0); FONT-SIZE: 12pt">d.<BR></DIV>
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<DIV dir=ltr id=divRplyFwdMsg><FONT style="FONT-SIZE: 11pt" color=#000000
face="Calibri, sans-serif"><B>From:</B> Synth-diy
<synth-diy-bounces@synth-diy.org> on behalf of David G Dixon
<dixon@mail.ubc.ca><BR><B>Sent:</B> December 31, 2018 8:24
AM<BR><B>To:</B> 'David G Dixon'; 'Oakley Sound'; 'Synth
DIY'<BR><B>Subject:</B> Re: [sdiy] Help, I'm Desperate! (Charge Injection with
DG408)</FONT>
<DIV> </DIV></DIV>
<DIV class=BodyFragment><FONT size=2><SPAN style="FONT-SIZE: 11pt">
<DIV class=PlainText>Hi All,<BR><BR>Remember this thread? Well, I have
some progress to report...<BR><BR>I took Roman's advice and used SPST analog
switches instead of multiplexers<BR>for my scanner. I just panelized the
prototype board, and it all works<BR>perfectly! The switching is
completely noise-free, as expected. Also, the<BR>board worked the first
time with no layout corrections needed, which is a<BR>bit of a surprise given
that this is a 4" x 6" one-sided PCB which is<BR>completely stuffed (12 ICs
and a pile of resistors and diodes).<BR><BR>This was not a terribly
straightforward redesign. First of all, the CV<BR>circuit was originally
designed to convert a -5V to +5V ramp to four<BR>truncated triangles from 5V
to 0V (5-0-5-0-5-0-5-0-5). This was perfect for<BR>9 channels, which my
original multiplexing scanner did. However, with the<BR>SPST scanner,
each channel requires its own switch, and the switches come<BR>four to a chip
(DG444), so this means only 8 channels. Hence, I want my<BR>triangles to
only go 5-0-5-0-5-0-5-0 (no final 5). This means that I want<BR>to
convert the ramp to 3.5 truncated triangles instead of 4. This took
some<BR>serious thinking, but was ultimately pretty easy to achieve, with only
a<BR>couple of additional opamps. I designed it so that if the incoming
CV<BR>signal is lower than -5V, the scanner will output Channel 1, and if it
is<BR>higher than +5V, the scanner will output Channel 8.<BR><BR>As for the
switching circuit, it required 6 comparators (LM339 + LM393), 8<BR>XNOR gates
(2 4077), and 8 SPST switches (2 DG444). I used hysteresis on<BR>the
comparators, and wired things up using Roman's "Fat Dot" concept.<BR>Actually,
the channels fall on two CV busses -- A and B (A is on when the<BR>2164 CV is
0V and B is on when the 2164 CV is 5V). Channels 1357 are on the<BR>B
bus (5V), and channels 2468 are on the A bus (0V). Rather than
thinking<BR>of the XNORs as providing fat dots, if one simply sees channels
1357 as one<BR>circuit, and 2468 as another circuit, with the XNORs
alternating between<BR>them, the one has two 4-channel logic circuits with
regular skinny dots.<BR>Either way, it works. Also, to clarify Roman's
schematic, the top and<BR>bottom comparators are not necessary. The top
one can be replaced with<BR>Ground, and the bottom one with 5V. Hence,
only 6 comparators are needed.<BR><BR>Also, I opted for "negative logic" in
this circuit, and thus used XNOR gates<BR>(4077) and DG444. However, it
would work just as well with "positive<BR>logic", which would use XOR gates
(4070) and DG445. These are<BR>pin-compatible with the others, so either
could be used on the same board.<BR><BR>Finally, the "client" had originally
wanted LEDs to indicate the channels.<BR>I had deemed this impossible with my
original circuit. However, it is very<BR>straightforward with this new
circuit. The XNOR outputs provide "ground"<BR>for the LEDs, and the
truncated triangle CV signal drives the LEDs. Since<BR>only one XNOR
output from either the 1357 or the 2468 side is on (at ground)<BR>at any given
time, only one LED from each bus will shine. The "inactive"<BR>LEDs have
5V instead of ground at their negative end, and therefore
cannot<BR>conduct. The triangles cause these two active LEDs to fade one
to the other<BR>in exactly the same fashion as the audio signals
themselves. Really, this<BR>works better than I could have hoped, and it
was very easy to do. I just<BR>had to invert and level shift the
truncated triangle CV signal so that one<BR>goes 5-0-5-0-5-0-5-0 while the
other goes 0-5-0-5-0-5-0-5, and use these two<BR>different signals to drive
the 1357 and 2468 LEDs, respectively. If<BR>"positive logic" were used
instead (with 4070 and DG445), then one would<BR>simply have to swap the CV
signals around and wire up the LEDs the other<BR>way.<BR><BR>I'm going to make
some kind of video to show how this works, and I'll put up<BR>a link here for
it. It will probably be tomorrow. I also plan to create a<BR>big
long thread on Muff Wiggler explaining the entire circuit in detail
with<BR>schematics and stuff, as a sort of tutorial on how I approach
design. I<BR>think that might be pretty useful for other
DIYers.<BR><BR>Thanks again for all your help, especially
Roman!!<BR><BR>Cheers,<BR>Dave<BR><BR>_______________________________________________<BR>Synth-diy
mailing list<BR>Synth-diy@synth-diy.org<BR><A
href="http://synth-diy.org/mailman/listinfo/synth-diy">http://synth-diy.org/mailman/listinfo/synth-diy</A><BR></DIV></SPAN></FONT></DIV></BLOCKQUOTE></BODY></HTML>