At 5:26 PM -0500 03/08/01, Tentochi wrote:
>
>I like this idea!
That's why I mentioned it :)
>The easiest way to get this function is to reprogram the chip.
Yes, that would be the most elegant method.
Another way which might be possible is to tap the trigger off of the
existing PCB (which would likely require a daughter board with at least a
voltage follower).
A third way would be to build an edge detecting daughter board connected to
the CV out of the UEG. It could be mummified in electrical tape and stuck
with double-sided tape somewhere.
The first two options require help from Encore. The third option does not.
If this seems somehow disrespectful, disloyal, unappreciative, or immoral,
to any of you, just try thinking of this as merely some guy trying to
differentiate a stepped function in his spare time :)
Since the dawn of man, I'm sure someone before us wanted to know whenever
the voltage of a signal jumped up or down. So I'm thinking a circuit that
does this is already out there. However, I'm not an EE, and all of my
"cookbooks" are about food.
Yet, I do have a copy of Horowitz & Hill. It just showed up one day in the
back yard. Using stone tools and coconut husks, I pieced together the
following circuit in my mind (please note that my primitive mind is one of
the worst places one could keep a circuit!):
Take the CV output of the UEG, run it through a voltage follower (as not to
draw too much current), to a differentiator. Figure 4.51 on page 224 looks
like a cap (C) going into the inverting input of an op-amp, with a resistor
(R) going from the op-amp's output to the inverting input, and the
non-inverting input going to ground, such that:
Vout = -RC dVin/dt
Since this looks like calculus I started jumping up and down "Oooh oook
oook! eee eek!!" :)
Then it says this circuit generally has "problems with noise and
instabilities at high frequencies because of the op-amp's high gain and
internal phase shifts". It shows a new circuit, with high-frequency
rolloff, in Figure 4.52. Yet it doesn't give a formula in which to
calculate the component values. Stupid aliens!! So I started hollering
and flinging poop at the monolith :)
Luckily he monolith ignored me, but I knew that even if I could get the
differentiator to work, I would end up with both negative and positive
voltages. So after this differentiatior, I would need an "absolute value
circuit" or "active full wave rectifier", I found two on page 222 and
started beating my chest :)
After that, I need to get this positive voltage up to approximately 5
volts, with enough current available to be used as a trigger. Is there a
comparator circuit that anyone would like to recommend?? I'm thinking a
LM339 with a pullup resistor connected to 5 volts would work.
Do they make comparators that will give a positive output regardless of the
polarity of the input voltage?? The table in Horowitz & Hill (pp. 584-585)
leads me to believe that an LM311 can, which would eliminate the need for
an absolute value circuit.
Does all of this monkey business make sense?? Does anyone know how to get
the circuit on in Figure 4.52 so that it will work??
>Tony has stated several times that most DIYers don't have the
>equipment to do this.
I certainly don't!!
>I haven't programmed any EPROMs for 15 years, so I am
>not up-to-date in this area and what geeks like us may have sitting
>around at home...
>
>It looks like all of the incoming data is available from all of the
>switches and you can program the output of each of the
>jacks--in particular, the TRIG OUT jack. You can check for LOOP ONLY mode.
>When in this mode, you could use one of the settings on the unused
>STEP/TRIG LOOP/RELEASE switch to turn on the "trigger out at the
>beginning of each step" mode. The location to check for this should be
>very obvious is the source code. And it should take too many extra lines
>of code to add:
>
>At the beginning of each step--
>
>Check for LOOP ONLY mode.
>
>Check for TRIG mode.
>
>Send trigger pulse to TRIG OUT.
>
>If anyone can read and burn these chips, I will be glad to help disect the
>code.
Thanks :) Does anyone know how to read and burn these chips?? Regardless,
building an edge detector might be easier than trying to re-write the code,
which could introduce a bug. Also, an edge detector circuit might be
useful with other things besides the UEG.