I finally conjured up an electronics project which scratched an itch of mine — while simultaneously allowing my buddy and I to design a custom hardware/software solution.
The Problem: ham folks use morse code ‘keyer’ devices to aid them. It’s basically a tiny computer that plays a morse code message in a loop. You program messages into a few memories on the device, then tell the device to play “CQ CQ CQ DE NN9S” in a loop while waiting for someone to hear your hail. Or maybe you program the device to give standard canned responses when you’re participating in a radio contest. Either way, I had this realization that the smartphone in my pocket was essentially a supercomputer; why on earth was I bothering to assemble little IC devices with 5 or 10 flash memories to do this job? My phone was infinitely more powerful.
So really, the question boils down to this: assuming we can write a phone app that plays any morse code we want, how do we convert a ‘beep’ sound into a signal that my radio thinks is equivalent to “pressing the straight key”?
The radio’s connector is quite simple: it sends a small current out of a jack. If the current comes back to it, it thinks you’re pressing down on the straight key (closing the circuit). The straight key is just a physical switch.
So Jack AI4SV (my mentor/elmer) designed a circuit below which uses a common NPN bipolar transistor as the switch; we simply need to tickle the transistor’s base with a bit of current from the phone’s audio, and poof, the transistor closes the radio’s circuit and the radio sends a ‘beep’ out the antenna.
Make a robot friend with Adafruit’s CRICKIT – A Creative Robotics & Interactive Construction Kit. It’s an add-on to our popular Circuit Playground Express, FEATHER and other platforms to make and program robots with CircuitPython, MakeCode, and Arduino. Start controlling motors, servos, solenoids. You also get signal pins, capacitive touch sensors, a NeoPixel driver and amplified speaker output. It complements & extends your boards so you can still use all the goodies on the microcontroller, now you have a robotics playground as well.
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