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The frame

I designed the PCB to mount in a frame that I also designed. It was to be milled out of Medium-density fiberboard (MDF). MDF is smooth, easy to cut and shape, and paints well. I have a friend, Denny, who is a retired cabinet maker who agreed to make the frame for my project free of charge! I was going to hire him to make more if I decide to start selling the clocks. That was becoming a real possibility since the clock was generating a lot of interest in those that I showed it to. However, after Denny made the frame for the Senior Project clock, he said he was not interested in making more! I guess it proved more difficult than he had thought. If I do sell clocks, I’ll have to either find someone else to make the frames or figure out how to do it myself.

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The board has been assembled

I assembled the board. Whew, that’s a lot of LEDs to solder! I adjusted the code for the test circuit to work on the new clock. However many of the LEDs refused to light!

At first, I thought I had a bad connection on one of the I/O lines, but then discovered what the actual problem was. Early on, I realized that the processor’s RA4 output was not suitable for driving the LEDs. This pin could only sink current, but not source it. The LED matrix required pins that could both source and sink current. Therefore, I had assigned this pin to drive the buzzer. All the buzzer needed was a current sink, so RA4 was dedicated to it. However, somewhere along the way, probably while laying out the PCB, I decided to switch some I/O lines around, and RA4 was connected to the LED matrix instead. So the LEDs that required a current source from RA4 were not lighting!

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Full schematic is complete

The full schematic for the clock is complete. Now I’m starting the layout of the PCB. This is going to be fun! Nearly 200 components to place, most of them in precise locations. I’m using a spreadsheet to calculate the exact coordinates and angles of the parts. And I’m going to manually route the traces myself. I’m hoping to put all the traces on the back side of the board except the 14 I/O lines for the LEDs will be on the front side in concentric circles among the LEDs.

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Test schematic

I created a test schematic to run 12 LEDs, the buzzer and three pushbuttons and monitor the 60Hz frequency. The LEDs and pushbuttons will be interfaced with just four I/O lines of the microcontroller This will allow me to test the concepts that will enable me to make the full circuit consisting of 182 LEDs and four pushbuttons interfaced to 14 I/O lines. For both the test and final circuits, the buzzer and 60Hz will each have a dedicated I/O line. Six I/O lines for the test circuit, and 16 I/O lines for the final clock circuit.