Monday, 1 May 2017

DL4YHF CW Keyer prototyped

With a bit of spare time this afternoon, and with Bob M1BBV sending 'do it!' messages to me, I got the CW Keyer prototyped onto breadboard. It would have been easy to go straight to PCB with this, but I wanted to prove the PIC chip had programmed correctly first.

video

Ive tried it on both 5v and 3v supplies with no issues, so due to the extremely low current drain, I will probably fit a holder for a 3v lithium coin cell in the finished, boxed keyer. My only issue with it is that there is a large part of the potentiometer track that seems to have no effect on the speed adjustment, meaning that the speed, especially slow speeds, is a bit tricky to set. Im sure i'll find a way around that though. I even managed to find a genuine old 2N2222A in a TO-18 package for the keying output!

The project is so simple that I will probably build it on a simple perforated prototype board, even Veroboard is a bit overkill for this! I have a nice little beige-grey plastic box to build it into. Extra to the schematic parts will be the coin cell holder, and connectors for the paddle key and radio. Both connectors will be common 3.5mm stereo jack sockets. The PIC will go in a DIL socket.

If your wondering what the extra parts to the left are for - thats another project! I also have an IR remote control tester prototyped on the same breadboard!

DL4YHF PIC CW Keyer using 16F628A with Semi-QSK Firmware


Following on from the above prototyping, Ive removed the 330pF and 3M3 resistor, as these are not needed by the firmware version im using, which uses internal settings for the clock. However, I still need to add in another 22k and 2N2222A to provide the QSK output (used to give a PTT to radios without their own in-built QSK, the FT-290Rmk1 being just such a set). A switch will also be added to turn the sidetone on/off as required.These are shown in the circuit diagram above.

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