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dk
Joined: Feb 12, 2019 Posts: 115 Location: Europe
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PHOBoS

Joined: Jan 14, 2010 Posts: 5810 Location: Moon Base
Audio files: 709
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Posted: Fri Nov 08, 2019 5:30 pm Post subject:
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Thanks for sharing
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 ) 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. _________________ "My perf, it's full of holes!"
http://phobos.000space.com/
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dk
Joined: Feb 12, 2019 Posts: 115 Location: Europe
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Posted: Sat Nov 09, 2019 3:09 am Post subject:
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Gut feeling says there isn't much of a need/market for 4-bit ADC chips anymore 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?
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.
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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

Joined: Jan 14, 2010 Posts: 5810 Location: Moon Base
Audio files: 709
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Posted: Sat Nov 09, 2019 5:48 am Post subject:
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dk wrote: | Gut feeling says there isn't much of a need/market for 4-bit ADC chips anymore 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? |
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. _________________ "My perf, it's full of holes!"
http://phobos.000space.com/
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