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

Posted: 10/9/2018 3:55:40 PM
Buggins

From: Theremin Motherland

Joined: 3/16/2017

Dewster, are you going to share / open source for the whole design?

Posted: 10/9/2018 4:59:52 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

"Dewster, are you going to share / open source for the whole design?"  - Buggins

Absolutely!  I already have in most ways, though rather informally.  Let me update the FPGA and firmware links:

- FPGA SystemVerilog code: [LINK]
- HIVE simulator C++ / Theremin firmware HAL (Hive assembly): [LINK]

Posted: 10/9/2018 5:16:18 PM
gerd

From: Germany (Black Forest)

Joined: 11/25/2017

Posted: 10/9/2018 7:15:03 PM
Buggins

From: Theremin Motherland

Joined: 3/16/2017

It's really great!

BTW, why not github or other source control site?

Posted: 10/9/2018 10:40:05 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

"BTW, why not github or other source control site?" - Buggins

Soon, kinda buried at the moment.

================

First Post Index

I finally started an index into this thread that might help those trying to get a quick grip on it.  See what you think: [LINK].

(I'm re-reading a lot of my own own words and fear I've come off as a bit of an arrogant old fool - so sorry!)

Posted: 10/10/2018 12:44:13 PM
pitts8rh

From: Minnesota USA

Joined: 11/27/2015


I'll add another post(s) with more information and a parts list as it develops.  If you want to get started you should order the FPGA board, and FPGA programmer, the encoders, the LEDs, the LCD, the EEPROM, and the other ICs.  I can provide you with coils and the SPDIF TX LED if you like, though the coil values might have to change if you go with traditional antennas.


Eric,

Can you recommend a specific FPGA board and programmer to order?  Remember, zero FPGA experience here...

Do you have schematics or PLs to identify the remaining parts that you described above so that I can get at least these ordered?  I can do the coils, and I would start with plates until things are working and I can work backward, if necessary, to adapt to rod and loop.  Not sure what the SPDIF TX LED is either, although if it is documented I can make that too.

My biggest question right now is where to find the basic design information (schematics and/or photos and parts list) for your current configuration.  I can hunt around a bit, but there is a lot of design evolution so I need to know where to start.  Any specific information on a few things to get ordered would be helpful.

Roger

Posted: 10/10/2018 2:43:15 PM
Buggins

From: Theremin Motherland

Joined: 3/16/2017


I finally started an index into this thread that might help those trying to get a quick grip on it.


Index makes this topic REALLY useful!

Posted: 10/10/2018 10:07:36 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Prototype Parts List

OK, spent the day trying to figure out what's in the prototype and where I got it from.  Amazon purchase history is excellent, eBay purchase history is almost worthless.  The 74LVU04N is unfortunately gone, and after looking at datasheets for a while (actual data in TI datasheets is really sparse) I believe the SN74AHC04N is likely similar enough.  Do socket it, if only for ESD purposes.  

I've got tons of Toslink TX modules if anyone needs one, but you can also just stick a red LED inside the converter if you are going the electrical RCA route exclusively.  I did this during testing and it worked fine.

On eBay the 7 segment display has conflicting critical info (common anode or cathode?) so buyer beware.  I did purchase this item from that seller, but it was quantity 5 rather than 10, so who knows.  You want common anode for the LED serial driver ICs, and you also want single diodes in the segments, not two diodes, which is common for larger displays, but raises the forward voltage too high for anything but red.

Also on eBay, the LCD was listed as 3.3V, they sent me a 3.3V logic / 5V panel, so they had to send me the level shifting parts to make it full 3.3V as advertised, so ditto.

I've got those questions into the eBay sellers, but haven't received any response yet.

As I believe I've said before, the ultra inexpensive rotary encoders from China seem to be better, from a contact bounce perspective anyway, than the more expensive encoders I bought from Adafruit.  If anyone knows where to get higher quality encoders for not too much, please let me know.

Next up: schematics.

--------
- GUTS -
--------
ITEM:   EP4CE6 EP4CE6E22C8N FPGA ALTERA Cyclone IV Development Evaluation Board Core Kit
SELLER: waveshare on eBay
LINK:   https://www.ebay.com/itm/251194059567
PRICE:  $28.20
QTY:    1
NOTES:  n/a

ITEM:   USB Blaster V2 Download Cable ALTERA FPGA CPLD EPCS16 EPC1/4 Programmer Debugger
SELLER: waveshare on eBay
LINK:   https://www.ebay.com/itm/251150460146
PRICE:  $20.23
QTY:    1
NOTES:  I have no experience with this as I have an old genuine Altera USB Blaster (with all of its board destroying faults).

ITEM:   Microchip 25LC1024 1 Mbit SPI Bus Serial EEPROM
SELLER: joaoccabral on eBay
LINK:   https://www.ebay.com/itm/123394475225
PRICE:  $3.05 + $3.80 s&h
QTY:    1
NOTES:  I bought 2 for some reason (probably to amortize the postage).

ITEM:   SN74AHC04N (hex inverter)
SELLER: mouser.com
LINK:   https://www.mouser.com/ProductDetail/Texas-Instruments/SN74AHC04N?qs=sGAEpiMZZMutVWjHE%2fYQw%2fPEs7KMKRQq6RY9CbibEkY%3d
PRICE:  $0.48
QTY:    2
NOTES:  One for each axis.  This should replace 74LVU04N which is unfortunately EOL.

ITEM:   SP721APP (ESD clamp array)
SELLER: mouser.com
LINK:   https://www.mouser.com/ProductDetail/Littelfuse/SP721APP?qs=%2fha2pyFadugLGwurnh9rv0x%252bpEqosLOt5%252bztt5r57Oc%3d
PRICE:  $2.40
QTY:    2
NOTES:  One for each axis.  Perhaps omit if antennas are insulated.

ITEM:   LP2950-33LPRE3 (LDO 3.3V voltage regulator - or equivalent)
SELLER: mouser.com
LINK:   https://www.mouser.com/ProductDetail/595-LP2950-33LPRE3
PRICE:  $0.46
QTY:    2
NOTES:  One for each axis.

ITEM:   TLC5916IN (LED serial driver)
SELLER: mouser.com
LINK:   https://www.mouser.com/ProductDetail/Texas-Instruments/TLC5916IN?qs=sGAEpiMZZMsE420DPIasPpR0nm8USuLtmpNyFAt1L4Y%3d
PRICE:  $1.36
QTY:    3
NOTES:  For the display board.

ITEM:   Toslink TX Transmitter Module
SELLER: Electronic Goldmine
LINK:   http://www.goldmine-elec-products.com/prodinfo.asp?number=G16911B
PRICE:  $37.25 / qty 25
QTY:    1
NOTES:  I HAVE TONS OF THESE!  You can also just cram a standard red LED into the Toslink SPDIF converter dog door.

ITEM:   Digital Optical Toslink or SPDIF Coax to Analog L/R RCA Audio Converter Adapter
SELLER: aotoper on eBay
LINK:   https://www.ebay.com/itm/302595988978
PRICE:  $3.89 + $2.99 s&h
QTY:    1
NOTES:  This includes an optical cable.

ITEM:   3.3V High Contrast 20x4 Character LCD Module Display,w/Tutorial,HD44780,Arduino
ITEM:   Manufaturer & part number: Eastrising ERM2004-2
SELLER: buydisplay on eBay
LINK:   https://www.ebay.com/itm/301965686712
PRICE:  $10.82
QTY:    1
NOTES:  Received 3.3V/5V display, had to bug them for the level shifter & solder it myself.

ITEM:   100pcs, 10mm Red Yellow Blue Green White Diffused Bright 5K MCD LED Leds Light
SELLER: colorfulplace888 on eBay
LINK:   https://www.ebay.com/itm/321297296247
PRICE:  $11.95
QTY:    1 batch.
NOTES:  The ones I received are clearly not 5K MCD, but they are bright enough and even.

ITEM:   10pcs 1 inch 1 Digital 7 Segments Led display Red Common Anode
ITEM:   Part number: KYX-1106BS
SELLER: uincelec on eBay
LINK:   https://www.ebay.com/itm/153199522097
PRICE:  $5.50 + $2.50 s&h
QTY:    1
NOTES:  Kinda big, slightly dim compared to 10mm LEDs but really OK.  I HAVE 4 OF THESE!

ITEM:   10 pieces 12 mm key switch rotary encoder switch Q1S3
SELLER: cpthreego on eBay
LINK:   https://www.ebay.com/itm/332747289811
PRICE:  $4.28
QTY:    8
NOTES:  20 detent with PB switch.  I bought from some other seller, these are likely the same.

ITEM:   Armorview PL2303HX USB To TTL To UART COM Cable Module Converter
SELLER: Dualmax on Amazon
LINK:   https://www.amazon.com/gp/product/B008AGDTA4
PRICE:  $6.99
QTY:    1
NOTES:  This provides power, EEPROM SW pump, Hive CLI.

------------
- PHYSICAL -
------------
ITEM:   Sterilite 1805 - Large FlipTop Box
SELLER: ??
LINK:   http://www.sterilite.com/SelectProduct.html?id=702&ProductCategory=249§ion=1
PRICE:  ??
QTY:    2
NOTES:  One for controls, one for pitch axis.  Got mine at Home Depot really cheap.

ITEM:   Sterilite 1803 2.5 Qt. Flip-Top Box
SELLER: Home depot
LINK:   https://www.homedepot.com/p/Sterilite-2-5-Qt-Flip-Top-Box-18038612/203002006
PRICE:  $2.28
QTY:    1
NOTES:  For volume axis.

ITEM:   RAM Mount Plastic Short Open Socket Arm System with Round Base and 1 inch Ball
SELLER: gpscity on eBay
LINK:   https://www.ebay.com/itm/172390522613
PRICE:  $12.49
QTY:    3
NOTES:  One for each axis box, one for control box.

ITEM:   RAM Mounts 2.5" Plastic Diameter Round AMPS Mounting Plate RAP-B-202U
SELLER: gpscity on eBay
LINK:   https://www.ebay.com/itm/201944848041
PRICE:  $6.49
QTY:    3
NOTES:  One for each axis box, one for control box.

ITEM:   Atlas AD11BE 5/8-Inch 27 Thread Surface Mount Female Microphone Flange, Ebony Finish
SELLER: Kellards on Amazon
LINK:   https://www.amazon.com/gp/product/B0002GY10M
PRICE:  $12.99
QTY:    1
NOTES:  Microphone stand mount.


--------
- MISC -
--------
- 2mH air core solenoid for pitch axis:
  - 260 turns single coat AWG32 on 1.5" PVC 40 former, OD 48.26 mm  (I did this) -OR-
  - 232 turns single coat AWG34 on 1.5" PVC 40 former, OD 48.26 mm  (to use same wire as volume side)
- 4mH air core solenoid for volume axis:
  - 295 turns single coat AWG34 on 2" PVC 40 former, OD 60.325 mm
- I buy my coil wire from techfixx: https://www.amazon.com/s?me=A169M3CDF2YEK0&page=1 single coat solderable.
- PVC 40 knockout end caps to mount coils w/ nylon screws.
- 2N3904 / 2N3906 or similar for coil drive (qty: 2 each)
- Handful of misc. passives including 2x 1pF or series equivalent.
- 40 pcs Dupont wire jumper cables 10cm 2.54mm female to female (qty: many, tear apart)
- 40 pcs Dupont wire jumper cables 20cm 2.54mm female to female (qty: many, tear apart)
- 1pc Double Side Prototype PCB Bread Board Tinned FR4 8 x 12 cm 80x 120mm (qty: 1, if hand wiring display)
- 10pc Plastic Round Screw type Knob PN-8F ( PN-38D ) ?15.5x14.2mm h=?6.4mm RoHS (qty: 8)
- 6" Aluminum sheet flashing (or similar) for antenna plates
- CAT5 cable, preferably stranded
- Nylon wire strain relief (several)
- Pin headers, IC sockets (I do DIY sockets from in-line stock)
- Power switch (mini toggle)
- 3 meter USB 2 or 3 extender cable (Amazon basics).
- Stick of wood to mount it all on, the grungier the better (it's a prototype, it's supposed to be ugly!).

Posted: 10/11/2018 12:23:50 AM
pitts8rh

From: Minnesota USA

Joined: 11/27/2015

I've already started ordering. The links are a huge help.  Thanks for this!

Posted: 10/11/2018 5:29:53 AM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

"I've already started ordering. The links are a huge help.  Thanks for this!" - pitts8rh

Sure! I am sincerely looking forward to where this is going.  Let me know if you want a TOSLINK TX part, or one of my 7-segment displays, as I have spares just sitting around doing nothing.

When winding the coils, I suggest cutting the PVC pipe former as long as will fit in the box, then offsetting the windings to one end so as to get them as far away from the plate as possible when the pipe is mounted perpendicular to the center of the plate (the high impedance end of the coil should be on the plate side, the low impedance end away from the plate).  An inch or so between the nearest winding and the plate should sufficiently minimize magnetic coupling (plate looks like a short turn), but the farther the better.  Start winding 5 or 10 mm from one end (the low impedance end) and wind in.  The coil winding height for both is less than 50mm if you're following the instructions above for making duplicates of what's in the prototype.  

I encourage you to check all of this with my spreadsheet [LINK] or the INCA software before you wind or even purchase wire; for your own reasons you may want to explore and use other coil geometries or wire gauges.  A 1:1 coil height:diameter is a reasonable soft target, though height > diameter can give you a bit less self C.  I haven't found significant Q reduction with thinner wire (which should give larger R loss), but really thin wire (36AWG and finer) can be a bear to handle so I avoid it. Use single coat insulated wire to get the turns as close as possible, and get the type of insulation that melts with solder so you don't have to strip it.  I drill tiny holes in the former, solder wire wrap wire to the coil ends, and feed this through the holes, coating it and the end windings in clear nail polish.  Encase the entire thing in thin battery pack type clear heat shrink tubing to make it more durable.  Glue a pipe knockout into the plate end, drill a hole in the center of the knockout, and affix both coil and plate to the axis box with a nylon screw & nut.  I'm using a small coil spring on the plate to electrically attach the coil end wire and the 1pF sense cap to the plate; a solder lug here would be more secure.

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