Let's Design and Build a (mostly) Digital Theremin!

Posted: 8/19/2016 9:12:58 PM

From: 60 Miles North of San Diego, CA

Joined: 10/1/2014

Posted: 8/21/2016 3:35:02 PM

From: Northern NJ, USA

Joined: 2/17/2012

Panel Layout

Playing around with various rotary encoder layouts:

The left option is obviously the most symmetrical, so it would be best for an ambidextrous controller box, and it would also allow for the smallest physical controller box in the vertical direction.  The center option appeals to me because the LCD has 4 lines, and giving the knobs some vertical association / correspondence with the LCD lines would make the interface more intuitive (I'm strongly considering having the hierarchical UI based on knob per line control) albeit less ambidextrous.  The angle the knobs takes in the center option is also fairly ergonomic for a non-south-paw, allowing tight knob spacing without too much interference between the manipulation of them.  The right option is a blend of the first two.

I'm struggling with which one to do because my inner cheapskate is screaming at me to do the center one so as to not to consume another LED display sized protoboard (I only have two, but I have tons of these smaller protoboards).  But other parts of my brain like the other two options better and dislike the relatively cramped center one.  Knobs that are too close together could be disastrous in a live performance parameter manipulation scenario, but having them close would likely speed up editing.  What to do?

I could just wire the switches and pull-ups in the air, but that might be risky in terms of shorts and stuff.

[EDIT] My inner cheapskate won.  Wiring it up now.

Posted: 8/23/2016 2:06:30 PM

From: Northern NJ, USA

Joined: 2/17/2012

I mounted the LED tuner, LCD module, and rotary encoder board in the prototype box yesterday (imagine the middle image above but with the stuff mounted beneath the translucent plastic top). 

Today I'm doing an FPGA pin inventory and am thinking about power distribution as there are only two +5 pins, two +3.3 pins, and four ground pins on the FPGA headers.  There are 80 I/O pins brought out to the FPGA board headers, and the Theremin requires somewhere around 40, so it's not a squeaker in terms of pin count.  Thinking of integrating the SPI Flash, SPDIF Toslink TX, and UART interface on a small board, with multiple power and ground breakout pins.  Once the pins are assigned I can move on to the oscillator interface modules at the antennas, which will mark the end of the hardware integration phase and the beginning of the serious (non-toycode) software phase.

Got a sale email from Electronic Goldmine this morning and strangely they have Toslink TX modules on sale, 25 for $5, so I rashly ordered 50 (one for every serious Thereminist in the world ;-):

I threw in a bag of 100 0.5pF-5.6pF adjustable caps for $5:

Because at some point I may try my hand at making an analog Theremin or two.

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