Last night was the start of another round of my cycle of electronics and embedded programming classes at the Columbus Idea Foundry. It begins with basic electronics, covering the fundamentals of DC electricity and simple lights-and-switches circuits, then on later nights, the follow-on classes add a programmable component, Arduino or Raspberry Pi. Students are free to sign up for individual classes or the whole series. For the first night, we begin by going over current flow, batteries, resistors, and LEDs, then build our first circuit:
The simplest complete circuit is a battery and a resistor (a power source and a load), but it’s not exciting to watch. Because the focus of the class is digital electronics and interfacing to microcontrollers, the simplest “interesting” circuit is a battery, an LED, a current-limiting resistor (to protect the LED) and a switch to make and break the circuit, pulsing the light on and off.
One step up from the simple switched LED circuit is a transistorized LED circuit. A 2N2222 general-purpose NPN transistor takes the place of the pushbutton from the previous circuit, then the pushbutton moves back a step to activate the transistor through its base leg. While the circuit seems to be the same on the surface, the identical behavior belies the princimple at hand, which is a small current switching a secondary current. If that secondary current is similar to the first, we call it “switching”. If it’s larger, we call it amplification. This simple circuit is powered by a single 6V power source and the pushbutton is capable of handling far more current than the LED, so it would be considered an application of switching. With an additional battery and a slight rearrangement of the wires, it’s easy to turn this into a demonstration of amplification.
The final circuit is an LED blinker based on the venerable but versatile 555 Timer IC. This circuit has enough connection points that building and debugging it takes almost 1/3 of the total class time, but it gives a great amount of satisfaction to put it all together and see it blink. The biggest challenges are getting all the right parts in the right breadboard holes and not bumping parts during the construction. Twisting the variable resistor changes the blink rate, and that leads into a quick preview of the Introduction to Arduino class, describing how the Atmel microcontroller takes the place of the 555, but rather than change hardware to change the rate, they will change software to change the rate (or to respond to buttons or to read a variable resistor, etc.) After spending the time to build a blinker from hardware, the students definitely begin to appreciate how much quicker it is to change a line of code than to swap out components, and why most devices made these days have a microprocessor instead of being hard-wired. Half of this class is already registered for the next one, one of the best indicators of success I could wish for.
As of this writing, there are still seats available for both Arduino and Raspberry Pi classes in November
Here’s the Student Kit:
- Battery-powered handheld Digital Meter
- Wire cutters
- 170-pin solderless breadboard
- Quad AA-battery pack (6VDC)
- Pushbutton switch
- Red LED
- Green LED
- 1K resistor
- 10K resistor
- 100K resistor
- 10K variable resistor
- 10uF capacitor
- 2N2222 NPN transistor
- 555 timer integrated circuit
- Assorted breadboard wires