multiple hysteresis oscillators

[dr.benway]

Just built the hysteresis oscillator and while I find it pretty cool I was looking for a way to get more bell-like tones and resonance. For now I've just put two circuits in parallel (signal splitter eventually) and while the sound is a little more dissonant it's not as interesting as I hoped. Will changing anything (cap values for instance?) on one of the circuits allow to alter the tonal range and increase the interaction between the two oscillators? 


Thanks for reading and I hope someone's got some ideas.

[sean k]

Got a link there Mr?

[dr.benway]

http://i49.photobucket.com/albums/f295/choklitlove/worthekik%20layouts/hysteresisschematic.gif

http://www.aronnelson.com/gallery/main.php/v/Choklitloves-album/album16/hysteresisoscillatorlayout.png.html

[sean k]

Looks kinda weird to me but I don't know enough about 555's to really say.

In monostable mode, which is how I usually use them, pin 7 goes to power through a resistance and then pin 7 also goes through a resistance to pin 6 and 2 which then have cap to ground. Pin 3 is the modulation input, if I remeber anything at all, or is it 5 and the output is pin 3?

But I'm just thinking that it doesn't seem quite right so I suppose I'll have to make one and see what happens then get entirely confused when I try to understand it while looking through my 555 book and still not getting the concept of flip flops... Sorry.

[earthtonesaudio]

The oscillators themselves will not interact unless you do something drastic.

For instance, use a third (low frequency) oscillator to light two LEDs.  One points to a photocell that makes signal oscillator A go faster, the other points to another photocell that makes oscillator B go slower.

[dr.benway]

The oscillators themselves will not interact unless you do something drastic.

For instance, use a third (low frequency) oscillator to light two LEDs.  One points to a photocell that makes signal oscillator A go faster, the other points to another photocell that makes oscillator B go slower.

Sounds good
Will a 40106 do ? If I understand correctly, the third oscillator powers two LDRs, but how is each photocell connected to its 555 ?

[Taylor]

If you want bell-like tones you should try putting them into the 2 inputs of a passive ring modulator:

http://www.asciipr0n.com/4096/ringmod/schematic.jpg

Though I'm assuming this is a noisy oscillator, so it's not going to sound pretty like nice bells.

[earthtonesaudio]

Sounds good
Will a 40106 do ? If I understand correctly, the third oscillator powers two LDRs, but how is each photocell connected to its 555 ?

Well, for starters you could use one of the gates from the 40106 in place of each 555 oscillator.  The pin 7 output on the 555 is an open collector/drain so you can duplicate that by adding on a single transistor for each section. 

To make the oscillator frequency increase with more light, put the photocell in parallel with the frequency-setting resistor in the hysteresis oscillator.  To make the frequency decrease, it's a little more complicated but can be done several ways.  The simplest I can think of is to use a second timing cap for that oscillator, and put the photocell in series with this extra cap.

[dr.benway]

Thanks earthtonesaudio! Will try that out and get back shortly if anything interesting happens. I'm a beginner so it might take me a while.
Perhaps what I'm after already exists elsewhere on the forum. Will keep digging.

[PRR]

Ug. It's a metal-beak woodpecker attacking your sound.

The "100 ohms" is clearly meant to be 100K; 33K there and 250K out-pot might give less loss. The 0.33u caps could be smaller, try what you have handy.

Two or three 555 choppers would be different from just one, but I don't think more 555 is really going to be "more mojo". And it will literally be less guitar.... at some point you are no longer in the picture, replaced by a buck of chips.

It gives 20% of the effect of a real ring-modulator for 2% of the cost. Good clean fun. But asking for "more bell-like tones" is asking the silk purse from the sow's ear. 

[dr.benway]

You're right. I was kidding myself about the bell tones, but hoping to get some more dynamic interaction.
Not really mojo I know. I was looking for something to use to play along with a dual oscillator...drone sounds.
I'll make the changes you suggested...could you just explain what the "discharge" in the schematic means ?


Thanks

[PRR]

> explain what the "discharge" in the schematic means ?

I never memorized 555 pin numbers, so I made a note of the key pins. Altho most are obvious by where they go and what it does.

"Discharge" pin is intended to DUMP the charge on the timing capacitor. A transistor to ground goes dead-short at the end of the cycle. That's why I thought "metal-beak woodpecker". It's clever, but brutal.