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Thread: Which hardware improvement(s) to reduce noise on Teensy analog inputs?

  1. #1
    Senior Member
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    Which hardware improvement(s) to reduce noise on Teensy analog inputs?

    Hello,

    I have an homemade sensorbox with a dozen of sliders connected to a Teensy 3.2. I want to use the highest possible ADC resolution but I cannot achieve more than 9 bits without filtering. I have tested several filter types (including the ResponsiveAnalogRead library) and I've had the best results with a median filter.

    I would like to improve the the hardware setup. I already have a capacitor between the + and ground on every fader.

    What would provide the best results?
    1. Power the box with a clean, separate power source instead of the USB?
    2. Cover the inside of the wooden box with metal and connect this metal to the ground (shielding)?
    3. Connect the sliders to the Teensy over a PCB instead of wires?

    Thank you.

  2. #2
    Senior Member
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    Trimmed mean will typically slightly outperform median. But post a schematic to show what you are doing with hardware.

  3. #3
    Senior Member
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    Is this a "spare no expense" project, or a "get the best results without going overboard" project?

    The ADCs in the Teensy 3.2 microcontroller can pull enough current during sampling that they appear to produce noise-like results. So a good way to handle that situation is to place an amplifier between the slider / pot / sense circuit and the Teensy's ADC input, though that's quite a bit more work.

    Alternatively given the fact the sliders' motion is controlled by human hands (true? or are they motorized?) it should be possible to use strong averaging or low pass filtering. Note that averaging and low pass filtering limit responsiveness.

    Edited to comment that my company's project uses Kinetis parts and we found that the switching current when starting ADC samples flatly required having a pretty carefully designed front-end.

  4. #4
    This might save you some work/stress/etc: My two cents would be to think about how many discrete steps a person could actually ever move a slider like this. Most midi controls are only 128 discrete steps and that is "enough" for sliders and knobs controlling realtime audio parameters. Granted, I think 128 steps is a bit low - but even with a very large knob or long slider I'm not able to move it in small enough increments to get 128 steps out of it.

    The idea of requiring 14, 15 or even 16 bits of useable steps for the location of a slider could very well be overkill.

    That being said, I've had promising results using the "Responsive Analog Read" library to read the location of potentiometers and it seems like I get an increase in useable resolution from the software side.

    https://github.com/dxinteractive/ResponsiveAnalogRead

    This is available in the Manage Libraries section of the arduino IDE.

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