pressure sensor paddles

[djbr1]

Proof Of Concept Pressure Sensor Paddles using strain sensor and ADC - Arduino Nano / CS1237 ADC implementation

(by HB9TXB)

Goal:

Powerful and flexible keyer with built-in reliable iambic paddle, easily built without specialised mechanical (machining) skills.

Why load sensor:

• Load sensor based paddle is self calibrating, sensitivity is adjustable from command line interface separately for dot and dash.
• In order to reduce backslash, existing mechanical paddle design utilize ball bearings. It is an overkill as angular (rotational) movement is almost non-existent.
• Mechanical contacts prone to bouncing.
• Minimal contact distance (0.1 mm) and minimal force (10 grams) difficult to maintain with mechanical paddles.
• More reliable compared to capacitive touch paddle, behaves like usual mechanical paddle.
• Sensor paddle is an order of magnitude cheaper than mechanical paddles.

Features:

• All K3NG capabilities available.
• Equally suitable for beginners and experts.
• Affordable, off the shelf, load sensor and ADC components. ( total approx. 10 USD for two ADC and two sensors ( ADC 2x1.3 USD, sensor 2 x 2~3 USD ))
• Boards: "compatible" Nano board 2 USD ; "compatible" ESP32 approx. 3-4 USD
• Can be developed as add-on to existing K3NG kits.

Two Prototypes:

1) Implementation based on ESP32 based k3ng keyer - SP5IOU has OLED SSD1306 display and command line interface over Bluetooth, allowing parameter change from Android Bluetooth Seria Terminal . Uses Hx711 ADC.

2. Arduino nano implementation, allows parameter change through USB interface using Android Serial Terminal app . CS1237 ADC is used.

TODO:

• Web Serial API for settings (as additional alternative to Bluetooth or USB Cable)
• PCB design
• BoM for additional components
• physical buttons as required
  • optocouplers and 3.5 mm jacks for PPT and TX line
• RFI/EMI shielding
• "paddle only" output if transceiver builtin keyer is preferred