IFD:Analog Circuits and Interfaces/interface schematics: Difference between revisions

Latest revision as of 15:22, 19 January 2023

This page shows a few ways to sense touch or force and convert it to an analog voltages.

This is a vintage style analog keyboard interface that is used e.g. on the stylophone to convert touches to pitches in 1V/Oct. More sophisticated version with note priority and touch/release detection can be found on music from outer space.

Velostat Pressure Sensor / Moisture-to-Voltage converter

This circuit can be used to detect finger pressure or any force on a surface with the help of a pressure sensitive sheet material called 'velotstat'. You can find a tutorial how to build the physical sensor here.

The same circuit can be used with a different type of physical interfaces as well. Instead of the velostat material as a variable resistor we can use a layout of wires known as a 'moisture sensor'. We can hookup our moisture sensor to the circuit above instead of the velostat sandwiched between two electrodes. Here is a video showing how to build a moisture sensor. Ciat Lonbarde's Tocante instrument might use this simple technique to sense touch.

Frequency Detector

To convert the frequency of a musical signal to a voltage, we can use this relative simple frequency detector circuit. Note that the output is linear in frequency, so it won't match the 1V/oct input of an analog synthesizer. That means pitches will be out of tune. Their might be ways to remedy this by using a logarithmic amplifier instead of the linear amplifier in the schematic. This is shown by the next schematic.

1V/Oct frequency detector

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 [http://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWEAWB0DsZnMwZgEwBsAHAJySkgKRUq5UCmAtGGAFABOITyhy3YdIW7IwwlkKjg4nEWIGSmuEguE0wMrkvw0J4-OnyqpGyLKUq93ArsFrpZrXeMt8xY+s0C3L4rcmejtz4+PxW4c6B5gZG4SFhkQ7mfi4EHklaaVbyVlFcfMassYmmsjnOBblJAObcCGDFivXFPjRmAM7WjeJZBeogAC4cAK4MbJ3lkjl94IMjY52VFWEzEEOj4+ANhdtMq3MbAEpb3SfBCPY0yP1tUNAIbADucuKVyu57-GbPFh9vOtw+k8urpKjFAV9gUxwZ9gqEIVAofEEeEgT9nLDXH9IeifJiUrDvtwCf8EUTtAjpjjwK9+JU0SB6fwimS2ABDcDYYk0UK6FLuMBIFhIUzwWxgaCkKXEPxwVhS0hkbwOeDArBhUjCdXedxE7VYkC8nWI55Gg1mlJ6rmwlmEzZMAkYklfWbrBbGiJ4-Zu+0Yv2Kb3ze3IuLwwmuoOdaGGFwwwMbKM2VIA8NrSPWSwY95kiMJl4uUS0kwHMYAeUN125IFwCFiKQg7CjvASimbObTGx+bcxhdZXaWTV2kTYxx4BRybctUkrrikbXu5jbE6ZJjFMgAHhXxKJDUqlO5mUYAF7DAA67QAkgAZADKAFE2JuQsVKARxPJD+AAGoAelLAGMBnPABBAA7dp-wACwAG2Gdp2kfRlYlwSAkBQ9BrEgIxPwAWwASyA9obwABzZUDQOGUDqgGBg8OghgOHPSiABNz1LUicOI88OAYNloLw9o8IYgZEMICBtAFBAPgIJBPxIsiKKogBHUZoPo0TYjcdR8EoaMMM-ao8IAI0IsAv3PNk4LYIA 1V/Oct analog keyboard interface]
-This is an vintage style analog keyboard interface that is used e.g. on the stylophone to convert touches to pitches in 1V/Oct. More sophisticated version with note priority and touch/release detection can be found on [http://musicfromouterspace.com/analogsynth_new/SINGLEBUSSKEYBOARD2007/SINGLEBUSSKEYBOARD2007.php music from outer space].
+This is a vintage style analog keyboard interface that is used e.g. on the stylophone to convert touches to pitches in 1V/Oct. More sophisticated version with note priority and touch/release detection can be found on [http://musicfromouterspace.com/analogsynth_new/SINGLEBUSSKEYBOARD2007/SINGLEBUSSKEYBOARD2007.php music from outer space].
 [http://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWcMBMcUHYMGZIA4UA2ATmIxAUgpABZsKBTAWjDACgAnEJ4wqb3iEFUw8SGzAYaAvixrSmeKkxp5wyMVFiQkAMQCWAOwDmDLgAUODAM7WArlbYB3GfxZ8qKNgCUQKFAqC-gqSHvw0Iij8VDAIEoRRwa5J7n4gACYMAGYAhnYANgAuTPkM6eoxWpDsXElgfEnCfvBsxn4BQg0d9ZXiLin1fhhRqV6F4MRRnh2VEDzQCCgIYAQIZLxgNKxaCAh4xAhYNGtgaIR0GhnZeUWcE1Od0Rpwzo-KgzGvPHxBHcKvKUEimU-wAHtxsLJTkhsGoWP5aOAojl8vl9MYcoUAPYcAA61gAxmiAA5scEsPBzC4sSDkFRUaSnEAotEY7F4wkksl+bDEcDYaTYMD0YXkRnI1HozE4-FE-Sk8EBEbC+hCqG4RFMllS9myrnkyRw+pGyB89xIRl8YlWWwOBhfIGqVyfA2EOmnEKbbinCCWkDWBiGaw47lLOa7PwEbiLTV8AAyAFEACLcphoZU0d2ib3yWMgGXWAC2WP01kKdrYQA Velostat Pressure Sensor / Moisture-to-Voltage converter]
+This circuit can be used to detect finger pressure or any force on a surface with the help of a pressure sensitive sheet material called 'velotstat'. You can find a tutorial how to build the physical sensor [https://learn.bela.io/tutorials/pure-data/sensors/diy-pressure-sensor/ here].
+The same circuit can be used with a different type of physical interfaces as well. Instead of the velostat material as a variable resistor we can use a layout of wires known as a 'moisture sensor'.
+We can hookup our moisture sensor to the circuit above instead of the velostat sandwiched between two electrodes.
+[https://www.youtube.com/watch?v=DT6nZsixP0M Here] is a video showing how to build a moisture sensor. [https://ciat-lonbarde.net/tocante/index.html Ciat Lonbarde's Tocante] instrument might use this simple technique to sense touch.
+[http://www.falstad.com/circuit/circuitjs.html?ctz=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-dAwN6mN7hN6wNBgf74z6fbCkxVHZx8NmJLK0I5PSBML7k0GQz7wzAozG4wmM96S2nYBmHZBaHgZm7hJh6kWo9MyxgqZWI1jMARkuHa-Hk1Hm5FQfjlzFkP72HSCdhnAwEDZQWr6pAANY6AD8LGoEhsADEILQxrzFRAb7JFCoNCwgA Frequency Detector]
+To convert the frequency of a musical signal to a voltage, we can use this relative simple frequency detector circuit. Note that the output is linear in frequency, so it won't match the 1V/oct input of an analog synthesizer. That means pitches will be out of tune. Their might be ways to remedy this by using a logarithmic amplifier instead of the linear amplifier in the schematic. This is shown by the next schematic.
+[http://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWEBmAHAJmgdgGzoRmACzICcpkORIC1SJNApgLRhgBQAHiM8glj3SpIPMoKwDq6amABqAegDyAYwAuAHQDOAMwBOjAI4BXRgDtlATy0ATRqsZqA9rvYBDceh7CeYHCObeqOBIrEhg8PBQ0KSoWDFYyFioCMiQRHA4UfHkWPio6URgqDgQ4RHsAO4ePkTUzOi5PKSZkJU+fjV1vv7erVX1jay17f7E1K1gpHW1QcxUPOn+8yLargA2moxR8AjsAEo8CGCec3UIpCfL4CCLIJhI91BRu8oLRLPzzEeX49sREMwsNAqJBcmA0KgLul0GAWMc-hxXvVUB86kJZr4njAIpByHj8QTyFlYjk8gUiiUEewAOaCFHtOlBETM9i6UQIH6MnhXMpwNrI1HVU5Qfl8Tm8DlNFpcBaNeG8NDBG7gTwAW0cpkcmlUrgARmtGFp5FoNYbNJoABaOVTsdLIN5Bd6idAiNieV3oAD6qE9kE9nFQqXBnoQvugYE9rE9XrA0Hwvs9x09yDDkHjrTt3OkN1mRGa4HhIhw3oTAaDKdDMAjUZjccrnuLKex6Zl9VIAgCJ3QOBCcWV8PCAGstAB+NqYoYyTLCvpSzpzgIs9zMfPCifzIJgEJb8A45mwCK1OJEBA4OIEdKkcFPXl8l0CdDZ5hOhonJ3URxGVQABy-NIXTortOyDuiKbJAV4owdIuN7wOw1gLmM4DTkhni2KsRhrDamYQU6IEFqBYBYA2RAJpepBhnglYHluVGRhGMbEcgtqQPaAyeIBSFuk8KZUGRuIUfcqbwO2PZ0TWybJm4BELEEj7TEEm7bmEe48Ni8DhDCBCkHwWAkO2aaweUtLcbwnimZiLJsuuMjyjycFVKZ8wWcMrTWfKqFPkhIjdqks7yfOAXPkyLH2scjpyaeMk+X6fF+uR0bQNRESiae8YSS6UnuScSGfN5dwunyBx5cMnGuU86QgKQWLPK2fgdkU-j8A1Ej9p4ACWpi-ja3DPsMrCoACyD9URjoqiAyifqY9i6PItj2E4Li9fgAJFDlFw+H2MgddNjDUroriqM4rZsKM+TgF0g1tSAayONSri6O1qgWqq7XKForiqt+aztdo7WMEtICtQNnjoMNm3VdtICaMo6xmp932-f9uhaAAFEdWhyEoagAJTsIqmQAGIQPaMiRKwICE-oxhmJY7BAA 1V/Oct frequency detector]