MOTM

does anyone know of an low frequency oscillator design that would give 
me an output similar to what is in the graph below?

http://www.etanstudios.com/images/dualoutoscgraph.gif

i've been working on this project for months now and i'm ready to rip my 
hair out. here's the scenario, i have two slide projectors, i've built 
dimmers for both lamps that accept a DC control voltage of up to 10VDC. 
what i want the projectors to do is similar to what a dissolve unit 
does, but at a variable rate of speed (0.1 Hz to 10Hz triangle wave) the 
voltage of output number one needs to start high and drop to zero, at 
the same time output 2 needs to start at zero and end up high in sync 
with output 1 going to zero. (the chart explains it better than i can) i 
cannot for the life of me figure out how to keep the entire triangle 
wave in the positive realm, nor have i been able to figure out an 
inverter to get output 2. i'm not that bright when it comes to 
electrical design, so any help would be appreciated... hell, i'll even 
pay someone (within reason) to draw up a schematic for me. if anyone has 
any insight into this, please email me privately so we don't piss off 
paul. and this is slightly synth related as we use this projection 
system during our shows, in which i am using the MOTM system (yeah, I 
know, that doesn't cut it...) thanks to everyone in advance for your 
help and tolerance. -nate

At 2:11 AM -0400 04/09/02, Nathan Hunsicker wrote:
>
>does anyone know of an low frequency oscillator design that would give
>me an output similar to what is in the graph below?
>
>http://www.etanstudios.com/images/dualoutoscgraph.gif

I don't do web on this machine, and I haven't finished my coffee.

>i've been working on this project for months now and i'm ready to rip my
>hair out. here's the scenario, i have two slide projectors, i've built
>dimmers for both lamps that accept a DC control voltage of up to 10VDC.
>what i want the projectors to do is similar to what a dissolve unit
>does, but at a variable rate of speed (0.1 Hz to 10Hz triangle wave) the
>voltage of output number one needs to start high and drop to zero,

You can offset and amplify the output of the 320.  Go to Larry's page, look
for "motm users/mark" (or something similar), and look at my 320 to pedal
converter.  Just change a resistor so that the second op-amp has a gain of
2, so it goes from 0 to +10V instead of 0 to +5V.

>at the same time output 2 needs to start at zero and end up high in sync
>with output 1 going to zero. (the chart explains it better than i can) i
>cannot for the life of me figure out how to keep the entire triangle
>wave in the positive realm, nor have i been able to figure out an
>inverter to get output 2.

The circuit to do this uses the same idea.  Take the 0 to +10V output of
the first circuit, invert it so it's 0 to -10V, then add +10V.  You can do
this with one inverted amp by summing the input with -10V.  So now an input
of 0 results in 10V, and an input of 10V results in 0V.

>i'm not that bright when it comes to electrical design, so any help would
>>be appreciated... hell, i'll even
>pay someone (within reason) to draw up a schematic for me.

I'm not that advanced either.  Compared to JH or OC, I'd have to draw that
schematic using my own poop ;)

>if anyone has any insight into this, please email me privately so we don't
>>piss off paul.

Well, anything that annoys Paul is automatically on-topic :)

>and this is slightly synth related as we use this projection
>system during our shows, in which i am using the MOTM system (yeah, I
>know, that doesn't cut it...)

As opposed to what, using the undead?? :)

>thanks to everyone in advance for your help and tolerance.

No problem, we're generally a pretty helpful bunch of knuckleheads.

This requires:

a) invert output #1to get #2
b) level shift both up (add +5V)

You can build a $2 circuit to do this. All it take is 1 TL074 Quad op amp and about 8 resistors.
You cam mount it on a MOTM breadboard behind a 1U blank panel. Or, you can use a MOTM-830 mixer,
and swap out 2 resistors to get the gain (it can already level shift).

Paul S.
*really* pissed :)