Morse Code Touch Keyer/Autocoder

Step 5: The Big Box

For the main circuit board I used a piece of stripboard which works well to connect the keypad to the pins on the Stamp.   Inputs from keypad are to PINS 0 to 11 and inputs from the touch keyer are to PINS 13 and 14.  The ground from the keyer goes to the ground rail.  PIN 12 is unused but should be buffered to ground anyway.  Output to relay is from PIN 15.  Connect the power (+ and – 9 volts) in to a couple of tracks, the DIT input to PIN 13 and the DAH input to PIN 14.  Note that these inputs are normally HIGH so connect 10K resistors to the +9V rail and the BS2 pins to buffer the inputs for each.  Use small gauge (24 or 26) stranded wire to connect the keypad to the PCB.  I used 22 gauge which made it kinda difficult to bend the mass of wires into the box.  Connect the common on the keypad to the +9 volt rail on the PCB and then all the keys to the stripboard (see my wiring diagram showing the BS2 I/O pins and inputs from keypad.)  The horizontal lines are jumpers (for #,9,6,3) to the opposite side of the BS2.  Your wiring diagram may be different, of course, and make sure you save it somewhere for future reference.  Inputs from the keypad are normally LOW so connect 10K resistors to the Ground rail and each INPUT PIN to buffer these inputs.

PIN 15 goes directly to the coil on the 5 volt relay (I know this is wrong and you should use a transistor to drive the relay according to BS guidance, but with a 5 volt relay it works fine.) The other pole of the coil is -9V, of course and don’t forget the anti-reversing diode across the coil.  I used a DPDT but a SPST would work too.  I used a DPDT because I added a small piezo beeper (to give me some feedback on my keying and to be used for practice) and two of the NO contacts fire the beeper.  The other two run to the jack that goes to the transmitter key.  OK, that’s all there is to the main board so on to the program.