Circuit and PC Board Design
This month we had a special treat as William Kommritz gave a presentation on “Choices in Circuit and PCB Design”; basically a peek at his electrical engineering technology education at Rochester Institute of Technology. [I mistakenly said he was a computer science student in the meeting preview.]
Will’s presentation was in two parts: first he showed us his senior project and discussed its design; then he took us thru the process of designing a very simple project and the steps to convert a breadboard prototype circuit to a printed circuit (PC) board that can be manufactured and soldered into a completed project.
Will’s senior project was a “Temperature, Light and Sound Meter” consisting of an Arduino, sensors, a 2-line screen, LEDs, control buttons, plus a few resistors mounted on a custom printed circuit board. Will used Fritzing, an open source application, to design the circuit board. More on this later. All of the components are housed in a small plastic case produced using a 3-D printer. The meter displays control menus and results on the two-line screen using software running on the Arduino.
The presentation now moved to the design process used to create the meter. To illustrate this process, Will used a simple timer circuit as an example. First we need a circuit, and Will showed us a typical breadboard prototype using a 555 integrated circuit to blink two LEDs. The goal is to produce a printed circuit board that does the exact same thing. To start, the circuit is transferred manually into Fritzing. Fritzing has a graphical representation of a breadboard. Very much like a CAD program, you place the electrical components on the breadboard exactly as they are on the prototype. Then you draw traces from point to point to create the circuit. When complete, it will look exactly like your physical breadboard except neater. Now Fritzing has a function that takes this circuit and makes a “rough cut” at a PC board layout. Again, Fritzing show the PC board on screen in the same colors and size as the final board. Now comes the tricky part, where you must unjumble the mess that Fritzing created automatically. While doing this, you must take design factors cross talk between traces and current loads into consideration. Fritzing has another helpful function that searches the layout for traces that cross or run too close. When you are satisfied with the design, Fritzing can then produce the files needed to have the board manufactured by several firms that provide this service to hobbyists as well as commercially.
The last step is to upload the design file (think of this as a CAD file) to the board manufacturer. The website Will used in the demo interpreted the design file and showed the board as it would be manufactured along with the cost for various numbers of boards. I was surprised at how low the price was for three copies of this very simple board. Will discussed several of these board manufacturers with their pluses and minuses.
Thank you to William Kommritz for his exceptional presentation. All in all it was a very informative meeting.
As of this writing, there is no topic for August. It would be nice to look at the world of Arduinos and similar microcontrollers. If anyone has a project you would like to share, even if it is not complete, please let me know. We could easily combine more than one project and discuss both trials and successes.