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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
CMOS Wave Shaper
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Cynosure
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PostPosted: Sat Mar 03, 2012 5:15 pm    Post subject: CMOS Wave Shaper
Subject description: Schematic
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I am sure that there are similar schematics floating around the web and some people might have posted them here already, but I drew this up for myself and figured I would share it just in case someone else could use it.

The source sqaurewave could come from anything, but in my schematic it is a 40106 oscillator. It runs a little high and is used as the clock frequency for the shift register. The same signal is also divided with a 4040 and used as the base input for the shift register. I do this dividing so that the spacing of the steps changes along with the pitch.

I added a couple of option at the output for more shaping. A cap to ground rounds it off into a nice sine wave. Passing the sound through a low value cap acts as a highpass filter that turns each edge of the step into a spike.

You could probably do some really weird wave shaping by using separate low or highpass filters on each output from the 4006. This might almost allow you to draw the desired waveform with a bit of practice.


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Standard stepped triangle.
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waveshapersine.jpg
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Sine wave.
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waveshaperspikes.jpg
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Spiked steps.
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cmosWaveShaper.gif


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bubzy



Joined: Oct 27, 2010
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PostPosted: Sun Mar 04, 2012 1:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

well, if this works, then its very interesting.
might breadboard it up tomorrow. Very Happy
nice work

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Sodium



Joined: Feb 11, 2012
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PostPosted: Sun Mar 04, 2012 1:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

Cynosure, that looks very nice, especially those spikes Smile. Does it perform with other input signals as well, or is it square in only?
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Sonic



Joined: Dec 02, 2010
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PostPosted: Sun Mar 04, 2012 2:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

This is very interesting indeed, Jake. I will try it out. It would be great to have an adjustable wave shaper module to accompany my 40106 VCO.
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Cynosure
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PostPosted: Sun Mar 04, 2012 5:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sodium - It might work with other waveforms if the peaks go over the CMOS threshold, but I think for optimal performance you will want to use a comparator to create a squarewave if you are using a different wave as the source.

Sonic - I was actually thinking about your vco when I was making it. It would be a cool module.

I was playing around with it today adding more or less of the shift register outputs, and changing the mixing resistors for diodes or small caps. You can make some very unique waveforms, but it is kind of difficult to predict how it is going to look and sound until you test it out.
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Sonic



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PostPosted: Sun Mar 04, 2012 5:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Cynosure wrote:
Sonic - I was actually thinking about your vco when I was making it. It would be a cool module.


Wow! Thanks so much!
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Cynosure
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PostPosted: Sun Mar 04, 2012 7:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

I also just created a similar stepped saw wave. I will make the schematic and post in a couple of days, but it is just a 4017 that has a different valued resistor on each output. Q1 has low resistance, Q9 has a lot of resistance, and Q10 isn't connected.


waveshapersaw.jpg
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waveshapersaw.jpg


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JingleJoe



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PostPosted: Mon Mar 05, 2012 3:11 am    Post subject: Reply with quote  Mark this post and the followings unread

Isn't it easier to get that saw wave from an R2R ladder and a 4040? Acctually probably about the same effort/parts are required for each.
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Cynosure
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PostPosted: Mon Mar 05, 2012 6:46 am    Post subject: Reply with quote  Mark this post and the followings unread

JingleJoe wrote:
Isn't it easier to get that saw wave from an R2R ladder and a 4040?

Maybe, but this is the idea I came up with. If you have another method, then please share.

I think it might be useful to put sliding pots on each output of the 4017 instead of fixed resistors. Then you could literally draw out any 10-bit waveform on the sliding pots.

Then add switchable highpass and lowpass filters to either smooth it out or make spikes.
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JingleJoe



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PostPosted: Mon Mar 05, 2012 2:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've seen that once before Smile used some different chips though if I remember rightly, you've come up with some good ideas here nevertheless Wink I look forwards to hearing some of these circuits Very Happy
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concretedog



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PostPosted: Tue Mar 06, 2012 6:51 am    Post subject: Reply with quote  Mark this post and the followings unread

Cynosure...this looks brilliant...I didn't realise I hd any 4006 but just found one...will breadboard this when I get chance...that sine wave image has me tempted!
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Nardu



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PostPosted: Wed Mar 07, 2012 5:59 am    Post subject: Reply with quote  Mark this post and the followings unread

128 steps staircase generator ; an R/2R ladder network and a 4024 .


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1.7b ramp.jpg


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Cynosure
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PostPosted: Wed Mar 07, 2012 11:19 am    Post subject: Reply with quote  Mark this post and the followings unread

Wow Nardu! That is amazing. Thanks for sharing.
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Nardu



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PostPosted: Wed Mar 07, 2012 2:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

4024 7b ramp oscillator stripboard (veroboard):


osc ramp 4024 discreet network.jpg
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osc ramp 4024 SIP network.jpg
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Cynosure
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PostPosted: Wed Mar 07, 2012 2:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

Can I substitute different resistor values? 150k and 75k are odd values that i do not have in quantity.

Would 47k and 100k work?
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corex



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PostPosted: Wed Mar 07, 2012 4:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

Cynosure wrote:
Can I substitute different resistor values? 150k and 75k are odd values that i do not have in quantity.

Would 47k and 100k work?

The ratio is important: R/2R. 47K is half of 100K, minus 6%. With an error of 6%, your error term is as large as your fourth bit (1/16th == 0.0625, ~6%). That means that you may as well only build a three-bit R/2R ladder.

See https://en.wikipedia.org/wiki/Resistor_ladder#Accuracy_of_R-2R_resistor_ladders
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fluxmonkey



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PostPosted: Wed Mar 07, 2012 6:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

but 47k and 94k (ie, 2 x 47k in series) would work...[/left]
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Nardu



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PostPosted: Thu Mar 08, 2012 3:51 am    Post subject: Reply with quote  Mark this post and the followings unread

Consider to use only 100k resistor. 2x100k in parallel = 50k.
Accuracy of R-2R resistor ladders for 7 bits is 1/127=0.79%
Discrete resistor should be 0.5% tolerance.
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Cynosure
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PostPosted: Thu Mar 08, 2012 6:42 am    Post subject: Reply with quote  Mark this post and the followings unread

Ok, so if I were to make it i would need to by resistors with better tolerance anyway, so i can get the same values.

Thanks!
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corex



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PostPosted: Thu Mar 08, 2012 11:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Nardu wrote:
Consider to use only 100k resistor. 2x100k in parallel = 50k.
Accuracy of R-2R resistor ladders for 7 bits is 1/127=0.79%
Discrete resistor should be 0.5% tolerance.


Yeah, this is the way to go. Especially easy if you've got a bin full of 100k 1%'s.
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JingleJoe



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PostPosted: Thu Mar 08, 2012 1:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

For an R2R ladder, unless you want to be precise and accurate, almost any value will work. I think I used resistors near 220k and 100k in my Lunetta death pipes from outer space. I didn't have enough you see? So I just put in any near values. Everything still worked fine, things were just a bit non-linear.
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Nardu



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PostPosted: Thu Mar 08, 2012 2:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

An R/2R ladder resistor network ... it's about a simple precise and accurate D/A converter.
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dougseidel



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PostPosted: Fri Mar 09, 2012 2:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

sometimes accurate and precise is either difficult to achieve, or just not as interesting. anyway, the ladder-shaped thing can be used to do all kinds of interesting translations of information.
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corex



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PostPosted: Mon Mar 12, 2012 5:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

dougseidel wrote:
sometimes accurate and precise is either difficult to achieve, or just not as interesting. anyway, the ladder-shaped thing can be used to do all kinds of interesting translations of information.

This is an excellent point, especially regarding Lunettas. Imprecision is part of the fun.
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Draal



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PostPosted: Tue Mar 13, 2012 9:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Nice info Smile . I approach the lunetta as a free form type of instrument, therefore precision isn't so important to me. I've done many versions of wave shapers, filters, adsr's, vco's and some of their complexity rivals that of modulars. Those machines rely on precise tolerances and ain't what I'm looking for in lunetta building.

Mosc clued many of us "in" long ago in reiterating the importance of keeping it simple with these circuits. Go ahead and make complicated modules but keep in mind they may not work the way you hoped. That is the Tao of Lunetta Very Happy

But by all means experiment; us ol timers enjoy the newly initiated and their zeal Twisted Evil .

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