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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
Encoder + Frequency Modifier Idea
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dk



Joined: Feb 12, 2019
Posts: 26
Location: Europe

PostPosted: Fri Nov 08, 2019 3:44 pm    Post subject: Encoder + Frequency Modifier Idea Reply with quote  Mark this post and the followings unread

Hello all,

I had an idea that I haven't come across here before, and thought I'd share with the class. I don't have the ability to breadboard it, but perhaps someone will chip in who understands things a bit deeper than I do to say whether it's utter bollocks or possibly a decent idea?

The thought occurred to me while drooling over frequency shifters and the like on youtube (as do most good ideas), that we could take our beloved 4089's and feed them a shifting binary code dependent on a CV or analog source. I thought of making a simple ADC feeding a priority encoder, which in turn would feed the 4089. Theoretically, you could stick pretty much any type of waveform or CV into it, and it doesn't have to exclusively feed a 4089... it could be anything with a binary input.

I made a quick block diagram below.

Any thoughts? A simpler way of doing this? Or maybe it's not worth the trouble?


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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Fri Nov 08, 2019 5:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for sharing Very Happy

yep, that should work.

I was actually wondering myself what would be an easy way to turn an analog signal into a binary one, like is there a single chip* solution ?
(no cheating with microprocessors Wink) That also came up after watching a youtube video, but it was about the Analog Solutions Generator
Sequencer which has a simple but neat way to control the gate output. It has 16 steps which are divided into 4 sections of 4 steps, and for
each section there is a knob that turns on the gate in a binary way. So the first knob controls the gate for steps 1,2,3,4 and if you rotate it
CW it goes from off, step 1, step 2, steps 1 & 2, step 3, steps 1 & 3, etc,.. up to steps 1 & 2 & 3 & 4.


* to clarify,. a single chip would of course be an ADC but is there in an easy to use one ? or maybe a rather different method.

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dk



Joined: Feb 12, 2019
Posts: 26
Location: Europe

PostPosted: Sat Nov 09, 2019 3:09 am    Post subject: Reply with quote  Mark this post and the followings unread

Gut feeling says there isn't much of a need/market for 4-bit ADC chips anymore Very Happy The smallest I can find is 8, although I guess it could just be hooked up partially?

Keeping things separate, though, I was thinking a 4532 could be used for a 3-bit encoder, or a 74HCT147 for a 4-bit. The latter only turns on it's last bit when everything's high, so it wouldn't need 16 but just 10 comparators on input. Obviously a purpose built chip would have a way more accurate comparator section (would a resistor array help here?), but this is still lunetta, right? Wink

Quote:
It has 16 steps which are divided into 4 sections of 4 steps, and for
each section there is a knob that turns on the gate in a binary way. So the first knob controls the gate for steps 1,2,3,4 and if you rotate it
CW it goes from off, step 1, step 2, steps 1 & 2, step 3, steps 1 & 3, etc,.. up to steps 1 & 2 & 3 & 4.


Oooh, interesting. Wouldn't feeding DC into this essentially act the same, though? (with the exception of bit 4... we'd need the encoder to actually be 16-into-4, which the 74HCT147 isn't)
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PHOBoS



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PostPosted: Sat Nov 09, 2019 5:48 am    Post subject: Reply with quote  Mark this post and the followings unread

dk wrote:
Gut feeling says there isn't much of a need/market for 4-bit ADC chips anymore Very Happy The smallest I can find is 8, although I guess it could just be hooked up partially?

yep, an 8-bit ADC would work fine, just ignore the lowest 4 bits. But a lot of them have a serial output and/or run at a certain frequency.
I actually used one of those for an 8-bit random generator. A flash ADC (which functions like the circuit you drew) would be much more convenient to use,
but I haven't really looked hard enough to find one.

Another method is using a folding ADC which is a bit like the equivalent of an R2R DAC. An example of that is the PAiA 4 Bit Digitizer at least I believe that
is a folding ADC. I did actually test it but if I recall correctly it had some problems with accuracy and I only got it to work up to 3 bits. I still have the circuit
so should be able to check that.
edit: found an easier looking one here but it would require some parallel/serial arrangements to get the correct resistor ratios.

Quote:
Obviously a purpose built chip would have a way more accurate comparator section (would a resistor array help here?), but this is still lunetta, right? Wink

You could use an LM3914 to replace the comparators and resistor network. It does need some inverters on the outputs but it might work
nicely with the 74HCT147. Resistor arrays would probably help with accuracy. Even if there is some tolerance in the overal resistance the
values themselves are likely to be close together which is the only thing that matters for this.

Quote:
ooh, interesting. Wouldn't feeding DC into this essentially act the same, though? (with the exception of bit 4... we'd need the encoder to actually be 16-into-4, which the 74HCT147 isn't)

yep, just a 4-bit ADC controlled with a DC voltage and some way to actually step through the bits. I was just thinking of doing similar but in a
different order which increases the number of steps that the gate is on instead of counting in binary. For example with 4 steps you'd get:
0000
0001
0010
0100
1000
0011
0101
1001
0110
1010
1100
0111
1011
1101
1110
1111

However that is not really easy to spread out over a couple of knobs (CV inputs) and for 8 steps you'd already have 256 variations which might
get a bit hard to set with a single knob, let alone 65536 variations for 16 steps. The analog solutions sequencer actually seems to have this funcion
to control all 16 steps with 1 CV labeled intensity.

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