Saturday, 13 May 2017

Building the DL4YHF Keyer

Having got the DL4YHF PIC CW Keyer working on breadboard, the next step was of course to make it a permanent build. I had already decided on the box I wanted to use, a small beige plastic one i'd picked up somewhere, and decided to use perfboard and hard wire the circuit, rather than muck about trying to design a PCB or waste my stock of Veroboard.

My first task then, was to size a piece of perfboard to fit the box. To do this two rows of holes needed to be removed, and the sides filed, plus the corner cut-outs. This allowed the board to fit easily down in the bottom of the box. I also decided to use a socket for the PIC chip, but couldnt find any 18pin DIL sockets, so had to bodge one from a couple of the 14pin sockets ive loads of. But probably the most important task was to search my junk boxes to find a holder for a 3v coin cell! The one I found was surface mount, but a few spare PCB pins soon had it in place.

Of course, after the build was complete, and while looking for something else entirely, I happened to find a load of 18pin DIL sockets!
The wiring on the underside is all point to point, mostly using the legs of the components themselves.

 With all the components installed, I checked it fitted the box, then drew out the circuit from the board, to make sure I hadnt missed anything or got anything wrong. This is well worth doing, but only practical for small projects. In the event, I'd missed a critical connection - the Vss line to the PIC!

 The final underside wiring is shown below. Im quite pleased that I managed to find a layout that had all the components on one side, as that meant the board would fit as low in the box as possible, giving me more space to work with. At this point I connected the board up to the speed control pot using croc clip leads and tested the keyer to make sure it was working.

So next came the work on the box itself. I was making the layout up as I went along, and the case and controls layout was no exception. A lot of work with files was needed, as I wanted to add a slide switch to allow me to turn off the sidetone. I also had to be careful where the output connectors went so as not to short the battery!

The 3.5mm stereo jack socket for the key caused trouble. The cheap ones i'd got proved that you get what you pay for! The act of tightening it up caused the damn thing to distort out of alignment such that I couldnt get a plug in! It took me quite a while to figure this out and correct it!

So with the board in place and the wiring ready, I turned my attention to the top panel. Initially I thought I would have to leave the project only part finished as I could only find one panel mounting push button. But I then decided to use a pair of very nice looking but PCB mounting square tactile buttons. This meant a lot more file work to create the square cutouts!

The buttons themselves had to be secured with hot-melt glue - trouble is, ive run out! So, I searched the workshop, salvaging little bits here and there, until I had enough to secure the two buttons. The speed control pot is also secured using its anti-slip stud - this involved some very careful drilling of 1.5mm blind holes!

The filed cutouts are not the neatest but are reasonably square and with the buttons in place dont look too bad. The light blue caps of the buttons go nicely with the beige colour of the box.

The final component to fit was the LED, which is used by the chip to indicate various special states. Everything was then tested again, before finally screwing up the box and adding a control knob.

And here it is, connected to my Hi-Mound paddles. The volume level of the sidetone is rather low, even with the sound holes drilled in the side, but its adequate.

I now need to build the cables to connect it to my radios! The speed range is a bit wide for my purposes, but thats something to sort out at a later date. Ive found a spot which gives around 8-12wpm, which is where I want it.

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