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Digital FD-8 pedal

From Just in Time

Revision as of 02:06, 7 February 2014 by Danny (talk | contribs)

In Roland FD-8 Issues: Hall Sensor Modification we described how a ratiometric hall sensor could replace the resistor film to solve reliability issues with the Roland FD-8 high hat pedals. Even though that Hall Sensor hack works, an MCU based approach might have some additional advantages:

  • complete variable resistance to be compatible with other drum modules
  • adjustable sensitivity curve
  • detection of foot-down velocity (which is currently limited to one static velocity)
  • auto-calibration, i.e. no need for pots to set the right trigger points.

We're currently working on a "more digital" version, based on a MCU and a digital potentiometer. We're using the following hardware:

  • attiny13 MCU: 8-pin (6 io), 10-bit ADC.
  • Two MCP41010 digital potentiometers in series (10K each, because when we sourced it, a single 50K version was a lot more expensive on ebay).
  • Honeywell SS490 ratiometric hall effect sensor.

Additionally (and optionally) we're adding:

  • a switch (button) to start calibration
  • an LED, because every MCU project should have an LED

The circuit essentialy does the following: using the adc, the output voltage of the hall sensor is measured. This is then used to determine a corresponding resistance and that resistance value is programmed into the digital pots. Easy.