Does anyone know of a source of potentiometers which have a 90 degree rotation? These would be typically used for Pitchbend and Modulation in a MIDI controller keyboard. They’re not for a repair but for a new build so the format isn’t critical, 10k linear is ideal though.
I don’t know how you are going to implement this but usually these just use a part of the 300 degree rotation of a pot. The 90 degree rotation is then achieved by physical boundaries for the wheel.
Most of the MIDI controller keyboards I’ve seen have 90 degree pots for Pitchbend and Modulation - this means that they have the processor Vcc across the pot and this is tapped by the wiper which gives the full range of voltage for the processor to convert.
It also saves the need to have different voltage rails in the design (rather like Shruthi and Ambika)
Erm, it’s rather done using standard pots and just parts of the viper movement, like 1.5V to 3.5V. You can either scale and process this in the ADC/software stage, or use some op-amps for voltage scaling vs the DAC reference.
Doepfer sells a modwheel kit, but it’s what shiftr describes - a mechanically constrained 270° pot, so you only get 30% of the full voltage. I’ve already seen a couple of synths with such a design.
This can be scaled by software, or if you’re scared of resolution loss, with an op-amp. Or if you have a voltage rail higher than the MCU voltage, you can divide it down so that the pot will output something in the correct range.
90 degrees is still the most elegant solution in that you obtain full resolution with the minimum components and only one supply rail.
Someone must make them but who?
I wouldn’t call “elegant” a solution that requires a custom-made or hard to find part. Especially if on the other side of the balance there’s 0.5 dual op-amp and 3 resistors.