R.G.'s sequencer

[Paul Perry (Frostwave)]

Maybe at slow speeds the shape of the output of the oscillator is bad? you could try toggling it with a switch & see how it behaves. unfortunately digital isn't my strength..

[Arno van der Heijden]

you could try toggling it with a switch & see how it behaves.

Hmmm... I'm not sure I understand that. Do you mean replacing the oscillator by a toggle switch?
How much does the oscillator put out? 9V?

[Arno van der Heijden]

bump

[The Tone God]

Hmmm... I'm not sure I understand that. Do you mean replacing the oscillator by a toggle switch?

Yes I belive that was the idea. The purpose is to figure out if the clock is driving the logic properly or if the is another issue with the logic itself.

Andrew

[Jason Stout]

I'm in!

Last night I breadboarded the Geo sequencer with Tim Escobedo's CMOS inverter twin T wha filter.  That was a mouthful!

I have a question...

Even though I had a blast adjusting pots while the filter was oscillating, I would like to know the best way to dampen the response of an inverter based twin T.

Arno van der Heijden, I haven't had a chance to listen to the random mode yet, when I can I'll let you know how mine performs.

[Jason Stout]

...Stole some time! My circuit works fine in up/down modes, and like Arno van der Heijden's it locks up(or is it down?) in random mode. I had time to toggle it myself, it works fine that way. next time i'm in the basement I'll have a look at the rate oscillator with the oscilloscope.

I haven't been this interested for a while, thanks to R.G. and Tim E. for the circuits!

[Arno van der Heijden]

The random mode works fine for me at higher speeds....

[Jason Stout]

The random mode works fine for me at higher speeds....

Me too, I still haven't had a chance to scope it out.

[Paul Perry (Frostwave)]

A lot of logic needs a "fast" enough rising (or falling) edge to trigger it. Maybe the LFO isn't shaarpening up enough.

[Jason Stout]

Thats what I think the problem is, I had a look on the scope and from what I can see (just watching the dot slowly cross the screen) mine is not very square at ~1 Hertz.

[Arno van der Heijden]

Does it have anything to do with the RC/diode combination?
Maybe this thread is of use:
http://www.diystompboxes.com/sboxforum/viewtopic.php?t=22978

[Jason Stout]

I'm stumped! The output of a Schmitt trigger oscillator should be nice and square, maybe my scope was fooling me, if I remember correctly Schmitt inverters can’t drive capacitive loads. Is this correct? if it is that might explain what I was seeing on my scope. Maybe tomorrow night I'll have another look, this time DC coupled. Frequencies this low are hard to watch with my old scope. I

I’ll try to look at the load input tomorrow as well.

R.G. what else should I look at/for?  All else works fine. Like I said I’m stumped.

[Jason Stout]

Ok, I DC coupled the oscillator output yesterday and it is indeed square! I then had a look while still DC coupled at the load input and I saw no pulse. OK so that’s my problem! I had a feeling that it was a loading problem and tried a 47 pF coupling cap instead of the 100pF in the Geofex schematic, nothing. I replaced the 100pF cap and then went to the 0.01µF cap, thinking if I made the pulse wider it would get through, replaced 0.01µF with 0.1µF, nothing still. I then made what I felt was a minute change to my breadboard layout and bam I have a clock pulse!

Component values are exactly as R.G. advised and random mode now works fine regardless of clock speed, with one exception, I have much more switching noise in random mode than I do in up/down modes. Is it my layout,  or is it inherent to the circuit?(I can’t see why it would be) ….I don't know, R.G. what do you think?

And…how possible is the addition of a glide circuit? I think can see the circuit required if we were dealing directly with voltages, but…???

I think gez just spoke of character building circuits; this one has been perfect for me!

[Arno van der Heijden]

I then made what I felt was a minute change to my breadboard layout and bam I have a clock pulse!

Jason, I don't understand what you are saying. What exactly did you change? Did you leave the 100pF cap in?

[Jason Stout]

Did you leave the 100pF cap in?

Yes, I did. The circuit components are exactly as R.G. specified.
The only change that I made was to my breadboard layout. I’ll check back in a bit -------- gotta go.

[R.G.]

Ok, I DC coupled the oscillator output yesterday and it is indeed square! I then had a look while still DC coupled at the load input and I saw no pulse. OK so that’s my problem! I had a feeling that it was a loading problem and tried a 47 pF coupling cap instead of the 100pF in the Geofex schematic, nothing. I replaced the 100pF cap and then went to the 0.01µF cap, thinking if I made the pulse wider it would get through, replaced 0.01µF with 0.1µF, nothing still. I then made what I felt was a minute change to my breadboard layout and bam I have a clock pulse!

Component values are exactly as R.G. advised and random mode now works fine regardless of clock speed,

Hmmm... that's weird. What minor change did you do, exactly?

Looking at it, I wonder if I made the load pulse too short. What happens if you just short the 100pF capacitor feeding the -Ld signal inverter?

with one exception, I have much more switching noise in random mode than I do in up/down modes. Is it my layout, or is it inherent to the circuit?(I can’t see why it would be) ….I don't know, R.G. what do you think?

I think layout. I would expect them to be equally good or bad. But Mother Nature may be trying to tell us something we haven't discovered yet. 8-)

And…how possible is the addition of a glide circuit? I think can see the circuit required if we were dealing directly with voltages, but…???

Yeah, glides are harder. To do it right, you need to build a little memory into the thing, possibly converting the output of the '193 into weighted currents into an LED/LDR for the wah. Then the glide could be how fast you let the LED current change.

[chumpito]

I have a schematic for the a "Morph-Lag" circuit for CV by Harry Bissell.  I thought I got it from here but if you want I can email it to you.

Found this also:


This also and has a pcb layout.
http://home.comcast.net/~sbernardi/elec/og2/og2_lag.html

[R.G.]

I have a schematic for the a "Morph-Lag" circuit for CV by Harry Bissell.

Wow! That's impressive! I'd have just used a resistor, a cap, and an opamp follower. I guess the ability to do independent up/down lags is important - that would have taken an additional two diode.

[chumpito]

Wow! That's impressive! I'd have just used a resistor, a cap, and an opamp follower. I guess the ability to do independent up/down lags is important - that would have taken an additional two diode.

Like the 3rd one listed :wink:

[Arno van der Heijden]

Mine still doesn't work right. If I short the 100pF cap the randomness gets worse.

BTW, the randomness could be a bit better at higher speeds as well.

I used the specified part values. Could it have anything to do with exact frequency of the 3 high frequency oscillators? Or the resistor values used for that? I used 1k, 680R and 560R. :?  :?