A couple of months ago, I realized that I hadn’t really built anything in a while. About that time, there was yet another discussion about whether to use a straight key or a paddle. The difference this time was that someone mentioned the Touch Paddle. These are devices that sense when someone touches a metal pad and electronically switches an output. There are two outputs, one for the dit and one for the dah.
The company that makes these devices, CW Touch Keyer, have a whole range of different products. Some have a built-in keyer. Some are just the paddles that you then have to connect to a keyer.
They even have a kit, the P3, which is what I opted to buy. At $20, it seemed a little steep, but what the heck. If it worked, it would be worth it.
What I received is different from the kit shown on their website. Mine uses surface-mount caps and resistors that were already soldered to the board. Assembly was really easy as I only had to solder in the two, eight-pin ICs; two transistors, a diode, an electrolytic cap, and a voltage regulator.
The hard part was figuring out how to make the dit and dah contacts. As shown in the photo above, I cut out a hunk of PC board material, and used a Dremel tool to file off some copper down the middle, creating two contacts. I hooked up 9 V from my bench power supply, and I had a working touch paddle.
Sort of, anyway. The problem with the setup as it is is that the touch pads are just floating. To work really well, I’m going to have to figure out some way to mount them somewhere, so that they don’t move around.
One funky thing about this kit is that the company has painted over the markings on the ICs. I guess he figured that since the circuit is so simple that someone would steal the design. I tried scraping the black paint off one of the ICs, but didn’t have any success with that.
A little Googling did the trick. I found the article, Touch Paddle Keyer, published in the March 2007 QST. The circuit shown in this article is almost identical to the circuit of my P3. The chip used in the article is the Atmel QT113-G, and while that part is no longer manufactured, DigiKey carries various types of the QT110, which would also work, if you wanted to roll your own.
I plan to figure out a good way to mount the paddles and then use this for the CW demo at the upcoming Mini-Maker Faire here in Ann Arbor. Kids should have fun playing with it.