They're really made to solder to a PCB, so I used a piece of very thin, flexible protoboard. It was proving impossible to solder wires to the number wheel whose pins don't work with any type of connector that I've found. This uses only 4 wires rather than the 12 needed if connecting directly to the LCD board. The LCD uses a "backpack" from Adafruit that communicates with the Arduino using the serial i2c protocol. Here's the back side of the faceplate with the display, button, speaker, speaker switch, LED, and number wheel. These are for the wires from the key, which plug into the connectors soldered to those rows. I think the only change from the wiring diagram above is the jumper wire from pin D2 to row 26 and the 3.3v to row 27. The PCB has power and ground rails on both sides, as in the wiring diagram, making it simpler to ground those pull-down resistors.Īnd here's the soldered board. For the "production" unit I used a PCB that has almost the same layout, making it easy to convert the prototype circuit to a permanent soldered version. Here's my prototype circuit on a breadboard without the LED, speaker, or the number wheel, though the connections are wired for those. (The current-limiting resistor required for the LED is soldered to the LED lead itself, where it is encased in heat-shrink tubing.) Anyway, I still am not certain whether the Nano, and this Nano clone in particular, has those resistors available on all the same pins as, say, the Uno. If I had used the built-in resistors, reversing the logic so that HIGH means an open circuit, I would have had no resistors on the board. My copy of Fritzing is broken, and this is quicker and easier anyway.Ĭoncerning all those pull-down resistors - I hadn't realized that the digital pins on an Arduino have built-in pull- up resistors available until after starting down this path. I came up with my own convention for this, but it should make sense. It's based very closely on the breadboarded prototype I'd been using. Here's the wiring diagram I drew up before starting to solder. It disables the beeping, making the wife happy. There is some leeway built into the code, of course, because hitting those values exactly is near impossible. That gives 0.075 seconds (60/800) for each dit, and 0.225 s for each dah. Dahs are 3x the length of dits, and there is a dit-length pause between letters PARIS is 50 dit-lengths long, so 16 wpm is 800 dit-lengths per minute. Words per minute is an odd metric because word lengths vary, and in Morse code even the lengths of letters vary. I didn't quite catch my hand on the key in the video, but you can see the key move. All other signaling in the video is by me on the key at the bottom of the screen. The wheel is read when the button is pushed, and the speed in words-per-minute is displayed on the LCD screen immediately followed by the sounding out and display of CQ at that speed. The ten-digit wheel centered under the screen selects from a list of expected input speeds.
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