Slide Mechanism Decisions

A project log for Digibone

A digital instrument with all the flare of a trombone, with the power and flexibility of an MIDI instrument

Craig HissettCraig Hissett 03/26/2019 at 13:481 Comment

Just a quick think-out-loud about how to read the slide positions for my pitch bending shenanigans.

I'm pretty much set on a slide frame with a freely moving handle inside. 30cm of travel would be great, as it would give me the following positions:

1st position - 0cm

2nd - 5cm

3rd - 10cm

4th - 15cm

5th - 20cm

6th - 25cm

7th - 30cm

It's just under half the size or a normal tenor trombone length, but it will be perfect for the compact build I am after :)

So far, I have two options for tracking positions on the slide:

1) encoder, belt & pulley

I like this idea; encoder at one end, handle connected to the belt to rotate the encoder. Would be easily enclosed, plus end switches at position 1 & 7 would help calibrate it.

2) Ultrasonic sensor

Fixed at the top, offset from the handle. The handle would have a small 'paddle' opposite the sensor.

Care would need to be taken to not have the hand on the handle affecting readings. This would make it like a shoulder mounted Theremin. I like theremins, ha ha ha.

I'm open to more suggestions :-)


Craig Hissett wrote 03/29/2019 at 21:50 point

a further note to this regarding the encoder method: rather than monitoring for air input before measuring it should be done the other way round to allow for constant monitoring of the position.

So, if the encoder value changes check the state of the air pressure, and if above the threshold send a note on value.

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