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### Topic: Help with options isolation (Read 413 times)previous topic - next topic

#### Grumpy_Mike

#15
##### Jan 14, 2019, 09:39 amLast Edit: Jan 14, 2019, 09:45 am by Grumpy_Mike
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Also to add. This device does not actually have any audio involved. It controls say the pitch of the audio or the rate of an lfo in the modulation of the audio. So it's all DC right? Not sure if this matter.
Yes it matters. It means you can't use the simple circuit I showed to give a DC bias.

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The synth operates at -5 to +5
So are you expecting the Arduino to output voltages over the range -5 to +5? That is a lot more complected.

What sort of resolution do you need?
When you put an analogue voltage into a digital system it turns that voltage into a number. For the Arduino those numbers go from 0 to 1023, to represent an input voltage of 0 to 5V. Is this granularity good enough for you?

When an Arduino outputs a voltage it only has a granularity of numbers 0 to 255 to represent voltages 0 to 5V.

These last two factors can be changed but only by adding external hardware.

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After the Arduino it gets put into an attenuverter which attenuates and inverts the 5v signal from the Arduino. Back to -5v to +5v. Then goes back to the synth for control.
So you have one of these attenuverter already or are you hoping to build one?

#### couka

#16
##### Jan 14, 2019, 09:44 am
When an Arduino outputs a voltage it only has a granularity of numbers 0 to 255 to represent voltages 0 to 5V.
... but even for that we need at least an RC-filter.
Don't send me technical questions via PM. They will be deleted unanswered.

#### Grumpy_Mike

#17
##### Jan 14, 2019, 09:49 amLast Edit: Jan 14, 2019, 09:51 am by Grumpy_Mike
... but even for that we need at least an RC-filter.
Yes indeed but the OP is into a lot of external circuitry as I see it. The input voltage conditioning is going to need op-amps with controlled offset and gain and I don't think the resolution of input or output is going to be high enough for his needs.

He says:-
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This is just something I started a few weeks ago because I need a controller that is not available on the consumer market.
And I think we both know why this sort of thing is not available as a consumer device.

#### dionnaki

#18
##### Jan 14, 2019, 02:27 pm
Yes I have an attenuverter built. It works fine with Arduino outputs. The attenuverter accepts +5v and converts to -5 - +5. Which I scan through with a potentiometer on each stage.

Without adding a voltage input everything works as expected. The Arduino selects the stages and stages output to the synth the way they are supposed to. At the moment I am just using a potentiometer connected to the Arduino. To represent the control voltage stage. I am assuming that if I swap the pot for a jack for a control voltage. It should work.

I just need to protect the inputs of the Arduino from the synth and it's fully functional. If I use a module from the synth that is strictly 0 -5v. Everything is ok. But the main module I want to work with runs on 12v and outputs -5-+5 or 0-5v.

I will get a picture drew up and see is this helps.

The analog voltage is converted to 0-1023 divided between 8 stages selected via a switch statement in the code. I should be fine if I can limit the input voltage to Arduino range I reckon. As I said it works now with no input stage attached.

#### Grumpy_Mike

#19
##### Jan 14, 2019, 03:21 pm
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I am assuming that if I swap the pot for a jack for a control voltage. It should work.