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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
RGB Shroom Synth
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PHOBoS



Joined: Jan 14, 2010
Posts: 1807
Location: Moon Base
Audio files: 351

PostPosted: Sat Oct 19, 2013 7:46 am    Post subject: RGB Shroom Synth
Subject description: it bleeps and blinks
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RingMad uploaded the following video:



which inspired me to do two things:
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
1st I wondered if the use of different colored filters in combination with the LDR's could produce a wider range of signals. So I made a little box
with 3 LDR's and a red, green and blue filter:
Posted Image, might have been reduced in size. Click Image to view fullscreen.
[note: the photo is taken before closing it]

and I tried making some comparators with NAND gate to get low/high signals from each LDR. Because of the hysteresis of the NAND gates
(4093) this didn't work too well so I ended up using opamps instead. As a light source I used a small 3.5" TV which seemed to work but I had to put
the LDR's pretty much on top of the screen. I also noticed that the blue one didn't work very well, and it reacted to green light almost the same as
blue light. This has to do with the spectrum the LDR is sensitive too which you can find some info on here of course it will also depend somewhat on
the type you use.

Because I had to put the LDR's so close to the screen, it would probably give a similar result without the colored filters. Also LDR's do react pretty
slow so you won't get any audio frequencies from them, so a photo-transistor might word experimenting with. I also did a test using the LDR's
directly to control the pitch of some oscillators similar to what RingMad did. Which pretty much sounds as you would expect.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------
The 2nd thing the video inspired me to do is pretty much unrelated to the previous experiments. I happen to have some LED mushrooms myself
which I've been wanting do something with. They're larger then the ones RingMad has and have bright white LED's powered by 4AA batteries. My
initial idea was to install some colored LED's and make it so I can control it with a lunetta patch to have some extra lights to go with the sound.
I found out that you can get some pretty random effects by clocking a shiftregister with an LFO and feeding a high frequency signal to the
data input. (It shouldn't be random but it's most likely caused by drifting of the used oscillators). A nice bonus with a using a shiftregister is that you
can link it to another one which is useful since I have 2 of those mushrooms Very Happy

To make them usable as blinking shrooms without the need for external control signals I added 2 oscillators. The CLK is provided by OSC A the
'data' by OSC B. I used the original on/off switch (which is mounted in such a way that it works by pressing the mushroom) to turn both
oscillators off, which is what the diodes on the inputs are for. Because turning them off results in a high output they are also both inverted (U1b, U1e).
To be able to use external signals as well without creating shorts I added OR gates using diodes and a pulldown resistor.

When the switch is closed there's also a pulse generated (1M resistors + 1nF cap + U1d) which resets the shiftregister, so It works like an on/off
switch when there are no external signals connected. The CLK output is buffered to prevent any problems when linking it to something else.
(It's also necessary for the ENV. GEN.)

This worked nice, but as usual you can always add moooore! Laughing
So besides LED's I added an R2R to the outputs of the shiftregister to create a CV for a VCO. At first I had them connected to the same outputs
as the LED's but I noticed on my scope that the LED's affected the voltage. The 4M7 resistor connected between the R2R and the (inv) CLK
causes a small pitch change after each note, and the 10nF capacitor creates a (very short) glide effect. Both are added to give the sound a bit
more shroom Wink

The VCO is just a CD4046 with a (de)range pot to have some control over the frequency. The 2M2 resistor attached to pin 12 makes sure it doesn't
go too low which I didn't like for this synth. The XOR gate inside the 4046 is used to create a ringmod signal from the VCO and the signal that is
used to control the data input of the shiftregister (OSC B or external). This creates a nice metallic sound. The frequency of OSC B is controlled
by an LDR mounted near the RGB LED's for even more shroominess.

The signal then passes through a simple env generator and 1 transistor VCA to create short sounds. In Step mode it produces a sound on every
CLK pulse in Funk mode it is controlled by the shifregister and is more random. Because the output of the shiftregsister often stays high for
several CLK cycles I added the diode and 1K resistor, so even if the output of the shiftregister stays high it will go low when the CLK does.

And by this point I pretty much reached the limit of what I could add in the available space. Actually it was quite a challenge to get everything in Shocked
I managed to make the PCB small enough to fit it inside the battery compartment. and had just enough room for the pots, connectors and
switches. I also had to keep the wires short because they take up space too, but with a bit of patience I got it all in and closed up Cool


I'm going to turn the other shroom into a little drumsynth. I allready got something breadboarded (demo below) but I'm not really happy with the
hi-hat yet. I might have to leave it out anyway because I only have limited space, and it also needs a control circuit. Probably something with a
shiftregister like the other shroom in combination with a divider (4040).


RGB Shroom Synth schematic.gif
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RGB Shroom Synth schematic.gif



RGB Shroom Synth - 01.jpg
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RGB Shroom Synth - 02.jpg
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PHOBoS - RGB Shroom Synth (Oct 19, 2013).mp3
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RGB Shroom Synth demo

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PHOBoS - RGB Shroom Synth & Drums (Oct 19, 2013).mp3
 Description:
RGB Shroom Synth and breadboarded drums

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 Filename:  PHOBoS - RGB Shroom Synth & Drums (Oct 19, 2013).mp3
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PHOBoS



Joined: Jan 14, 2010
Posts: 1807
Location: Moon Base
Audio files: 351

PostPosted: Sat Oct 19, 2013 7:49 am    Post subject: Reply with quote  Mark this post and the followings unread

and here's a demo of the RGB shroom synth together with the Lun-A-Key.


PHOBoS - RGB Shroom Synth & Lun-A-Key (Oct 17, 2013).mp3
 Description:
RGB Shroom Synth & Lun-A-Key

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 Filename:  PHOBoS - RGB Shroom Synth & Lun-A-Key (Oct 17, 2013).mp3
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RingMad



Joined: Jan 15, 2011
Posts: 233
Location: Montreal, Canada
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PostPosted: Mon Oct 21, 2013 3:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Well I'm glad my silly little video inspired a PHOBoS build! And I can't wait to get done with some must-be-done home improvement projects so I can finally finish my electronic box so I can clear the breadboards and try that random shiftregister circuit for myself.
I've seen those same mushrooms you used in the Dollarama here too.

James.
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jcintheus



Joined: Oct 16, 2011
Posts: 58
Location: Colorado

PostPosted: Mon Oct 21, 2013 7:02 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
The XOR gate inside the 4046 is used to create a ringmod

Wow!
Did you use pins 3 and 14 for the inputs and 2 for the output?
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PHOBoS



Joined: Jan 14, 2010
Posts: 1807
Location: Moon Base
Audio files: 351

PostPosted: Mon Oct 21, 2013 2:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

jcintheus wrote:
Did you use pins 3 and 14 for the inputs and 2 for the output?

yep. (see colorful schematic Wink)
it can also be used to create odd divisions.

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jcintheus



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Location: Colorado

PostPosted: Mon Oct 21, 2013 2:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

jcintheus wrote:
Quote:
The XOR gate inside the 4046 is used to create a ringmod

Wow!
Did you use pins 3 and 14 for the inputs and 2 for the output?


I've been thinking about this all day. I just got home from work, and tried it out on a breadboard.
It works like a charm.
To be sure, the rest of the 4046 is being used only as a VCO.
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PHOBoS



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Audio files: 351

PostPosted: Fri Oct 25, 2013 7:11 am    Post subject: RGB Shroom Drums Reply with quote  Mark this post and the followings unread

I finished the RGB Shroom drum and had some fun with it yesterday Very Happy (will post a part of that later). I left out the hi-hat and had just enough
room for 3 drum circuits and a shiftregister. So it doesn't have it's own oscillators, but I have the other shroom for that. The drum circuits I used
came from an old elektor magazine, which can also be found here.

I first tried a 4011 as used in the original schematic, and although it worked the output level was pretty low and there was some humming.
That's when I found that thread where bugbrand mentions using a CD4069 instead, so I gave that a try and it worked a lot better. I
experimented with some different capacitors until I had some sounds I liked and I also added a tuning options to 2 of the drums (I couldn't fit 3
pots in the mushroom). With the current values there is some self oscillation at certain settings. The bass drum actually kept oscillating
once I transferred it from breadboard to perf so I had to reduce the feedback resistor a bit (from 1.2M to 820K). I also noticed some clicks
which I got rid of for the most part with the added (shottky) diodes to GND.

The control circuit is just a shiftregister as I used for the other shroom to which it can be linked. But the drums can be triggered directly as well.
There are switches to turn each of the drums on/off but I did notice that even when they aren't triggered they still make a soft sound, which is
probably due to some noise on the power lines caused by the LED's. It would be better to use some (transistor) drivers for the LED's especially
the red one, but I simply didn't have room for it.


When I put it together it seems to work at first but I started to notice that the Synth Shroom was actually flashing a lot more then the Drum Shroom.
Which doesn't make sense because with the shiftregister linked they should behave the same although delayed. I breadboarded another
shiftregister with 3 LED's attached and that worked fine. So I tried swapping the chips but no success. I also tried pullup/pulldown resistors
and at some point I had my scope attached to it and that made it work Shocked So I managed to solve the problem with a small capacitor connected
between the data input and GND. I'm not sure what caused it, it might be a combination of noise on the power line and the voltage drop on the output
caused by the LED, but it works now Cool


RGB Shroom Drums - 01.jpg
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RGB Shroom Drums perf pr0n
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PHOBoS



Joined: Jan 14, 2010
Posts: 1807
Location: Moon Base
Audio files: 351

PostPosted: Fri Oct 25, 2013 7:13 am    Post subject: Reply with quote  Mark this post and the followings unread

here's a short video of both RGB Shrooms together.


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dougseidel



Joined: Feb 10, 2010
Posts: 63
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PostPosted: Mon Oct 28, 2013 4:57 am    Post subject: Reply with quote  Mark this post and the followings unread

those are perfect mushrooms
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