Using A Touch Sensor As A Telegraph Key

[Sebastian] is learning Morse code and CW radio, and of course he needed a telegraph key. Instead of using the terribly unergonomic paddle style key, he built a capacitive touch iambic key over the course of a few evenings.

An iambic key usually has two switches. When one switch is closed, it will transmit a ‘dit’. When the other switch is closed, it will transmit a ‘dah’. Instead of using mechanical paddles, [Sebastian] brought his iambic key into the 21st century by using a touch sensor. An ATtiny45 measures the time it takes for a single metal plate to fully charge. It’s the same idea behind the wonderful Arduino CapSense library.

This isn’t the first capacitive-touch iambic key we’ve seen; this little guy is just a pair of metal contacts and resistors that plug right into an Arduino. With an ATtiny45, [Sebastian]’s build is a full-blown iambic telegraph key that plugs right into his CW rig. You can check out the walk through of the project along with [Sebastian] trying out his iambic key after the break.


14 thoughts on “Using A Touch Sensor As A Telegraph Key

    1. Never heard of gmail tap. In the past when I have ever suggested in hacking or DIY forms, that texting could be enhanced is phone makers would include a “key” and morse code decoding/encoding software, that idea was derided. Perhaps I should looked into if the idea was patentable? With the advent of smart phones I wouldn’t be surprised that a amateur radio operator hasn’t already created an application that does this. Now that google has the idea I guess it’s cool, but not as cool if Apple done it first ;) Most likely its’ dead already because it requires an extra effort to learn morse in a word that’s addicted to plug and play. I can’t here it now. George are you playing packet pool? A red face George answers no I’m just texting.

  1. While this is a set of capacitive touch paddles that could be used with an iambic key/keyer, the project isn’t an iambic keyer. In the event it does automatic dot insertion I ,missed it here. Sebastian doesn’t mention mention iambic in his write up.

  2. Bah. If you’re going to talk ergonomics, you should also mention how the ‘pulp pinch’ (the motion being used in the picture) is also not that great over long periods. This will certainly increase your CTD Risk Index.

  3. Nice work, Sebastian. Just a quick note; most paddles use the old “bug” convention of the dit on the thumb and the dah on the index finger. Not everyone follows that convention, and many keyers let you swap. Many paddles go out of their way to add weight so they don’t skip around on the desktop. Keep practicing, and good luck!

    Hojo – the traditional key is good up to about 15-25 wpm (words per minute) for most hams. People using bugs and paddles can go faster still, with some doing upwards of 50wpm. I don’t recall what the top speed is, but it’s a lot faster than I ever will.

  4. Nice project ! I do it in less than 5 minutes…
    Got my ticket for 38 yrs ago and love a well done speedy CW ( but by ears – two of course… hi )

    Best 73/DX !


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