Some Old Works of Mine

I was doing some clean up and found some old works from years ago…

The one above is a multi-purpose PIC pad using PIC16F627. This was an exercise of multiplexing 7 segment LEDs and button matrix using the same set of I/O pins. I wrote code to make it work as a timer and organ (more like a beeper with notes). 2 AA battery holder was connected to it, but obviously lost.

This was done in April of 2003. Before Arduino and all that good stuff was available. Home etched and hand drilled PCB. What’s amazing to me now is that I designed the PCB in Adobe Illustrator! I did not have a CAD software.

> PCB Layout

Next up is my very first LED project using PIC microcontroller, which was done right around the same time as the pad above.

> Schematic
> PCB Layout

I used four microcontrollers on this one. three controlling LEDs, and another one controlling them. The center one is the “master”, sending command to the other controllers to orchestrate the animation. The three “slaves” are just controlling the LEDs as they are commanded. The setup seems more complicated than my recent projects, but back then I was literally applying “divide and conquer” method to the circuit design.
When I first envisioned this one, I had no knowledge of microcontroller. I had some electronics experience and knew how to use logic ICs, however it quickly became clear that what I wanted to do was too complicated to accomplish with logic ICs. So that prompted me to look around, which led me to BASIC Stamp. BASIC Stamp, for those who never hard of it, it’s kind of like a pre-Arduino. You can write the code in BASIC language and upload it to the chip over serial cable. It was easy to use, but the processor was very slow.
Faced by the limitation I decided to learn to code PIC microcontroller directly. It took me a while to get into, but I managed.

I made a revision of the same circuit, multiplying the number of LEDs by using a complementary drive approach. (July 2003)

> Schematic
> PCB Layout

After this prototype, I decided to move on up to manufactured PCB. Found a free PCB design software (called Osmond PCB – which I still use), and start having my PCB made by a factory. This enabled me to design with fine traces and more precision.

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