Steps

You are highly encouraged to do this with one or two other people who are simultaneously working on their own toolkits. One person should do the work hands-on while the other(s) observe, work to identify yet/not yet moments, and do explorations to help facilitate failing forward. After the first person reaches a certain point as agreed upon by the collaborative, then the other(s) will work through those same steps with support from the first person. In this way, pair programming will be implemented.

1. Remove the three resistors previously used with the LEDs from the breadboard. Leave the LEDs and jumper wires connected to the breadboard as is.
   
2. Add in three new 6 inch jumper wires as specified in the diagram.
   
3. Add back in one of the 560 Ω resistors into the location specified in the diagram.
   
4. Optionally, use pliers to straighten the four legs on a momentary switch.
   
5. Carefully insert the momentary switch into your breadboard in the specified pins from the diagram.
   
6. Use “Yet/Not Yet” troubleshooting to determine if:
   1. The LED in columns 27 and 28, row H comes on after connecting the switch to the breadboard.
   2. The LED in columns 27 and 28, and the LED in columns 36 and 37, both in row B, come on after the push button is pressed down.

• If “Not Yet” for either check, proceed to fail forward using our troubleshooting strategies:
  
  

Key Takeaways

The flow of an electric current through a circuit occurs in a predictable and controllable fashion and deductive reasoning serves exceptionally well in the exploration of these. As we saw in this exercise, no matter the physical change we make with the momentary switch push button, current always passes through the resistor and one leg of the momentary switch. Current then continues on to the lower LED on the breadboard before arriving at ground. The current will continue to flow through the circuit, as long as:

• The electrical components remain physically connected to the jumper wires and the metal conductors within the breadboard with sufficient magnitude.
• The five volts of power and ground remain connected to appropriate sources.

We also saw that when the push button is sufficiently pressed, current also flows to the other two legs of the switch. This incorporates the other two LEDs in series with the circuit.

We also compared the view of a circuit using schematics and diagrams, each seated next to the physical, constructed prototype. As we seek to demystify technology, we’ll continue to see how multiple points of view help to fill in gaps in our understanding of what is actually happening “beneath the hood,” and how we might implement it in our own works to shape its impact in our daily lives.

We’ve already discovered that if you increase the size of the resistor from 560 Ω to 10,000 Ω, the brightness of our 3mm white LED is reduced considerably. Indeed, the increased resistance dims the LED more than a reduction in the voltage of our electrical source from 5 volts to 3.3 volts.

When working with electrical conductors, there is a proportional relationship between three measurements influencing the passage of an electrical charge:

• Electromotive force, listed in volts (e.g., 5V, 3.3V)
• Electrical resistance, listed in ohms (e.g., 560 ohms, 10K ohms)
• Electrical current, listed as amperes, or amps

Recall earlier, we tested the influence of different voltages and different ohms on the brightness of an LED. As we increase voltage, we also increase brightness. On the other hand, as we increase the ohms of resistance, we decrease brightness. This is because voltage increases current, while resistance decreases current.

And it is current that is used by an LED to make light. More current, more light.

A fourth measurement, watts, is a comprehensive measurement of power as influenced by the above three measurements. You may recognize the term watts in relation to lighting, as in a 60 watt incandescent light bulb. An equivalent LED light bulb, in brightness, would use about 8.5 watts of power. Our little white LEDs use closer to 75 milliwatts (mW) of power.

Like lights everywhere, they dissipate power in a predictable physical manner, such that at a certain point increasing the number of LEDs within a defined circuit decreases the brightness of those LEDs. It is for this reason that we see the dimming of all three LEDs when the momentary switch is pressed and current passes through to all three LEDs simultaneously.

As more components are added within an electrical circuit, the flow of current remains the same, to the extent that it is a closed loop between current and ground. Components work in series to direct, redirect, and influence the force and resistance of the current passing through this loop in a range of ways.

Steps

1. Review the breadboard diagram below to identify the columns of the breadboard used in testing.
   
2. For fun, let’s try out two 10mm blue LEDs that came with the kit. For one, we’ll bring 5 volts to a 560 Ω resistor to the anode of the LED. We’ll connect the cathode of the LED to ground.
3. For the other, though, we’ll connect one pair of legs of the switch to 5 volts, and the other pair of legs to ground. In this way, pressing down on the push button will switch the 5 volts directly to ground, completing the circuit. We’ll also connect the 5 volt legs of the switch to the anode leg of the other 10mm blue LED. We’ll connect the cathode leg of that blue LED to ground as well.
4. With the above completed, compare the impacts on the LEDs of pressing the button on the two different circuits that incorporate switches.
5. Further, compare how the pressing of the two switches impacts the brightness of the LED in a standalone circuit.

Key Takeaways

From the Raspberry Pi, 50 milliamps (mA) of current flow from the voltage pins of the General Purpose Input Output (GPIO), which we have connected to the red rail on the breadboard using a jumper wire. In this way, we can connect each circuit to the red rail, thereby passing that 50 mA to the rest of each circuit. If there is only one LED within the circuit, it has access to the total power passing through that circuit. On the other hand, when there are three LEDs in series on that circuit, each draws some of the power from that circuit.

Take a moment to review the schematic below to compare how each of the three circuits establishes a complete and closed path in which current can flow. Compare this to the diagram showing the conductors and components used to form this complete and closed path.

• How did this exercise compare to past exercises in which you were encouraged to watch a video demonstration first and then proceed forward in programming pairs?
• How might you have designed the setup of these circuits on the breadboard to better achieve that which you value doing? Why?
• In what ways are you reconfiguring the layout of the circuit schematic on the breadboard? In what ways are you designing a new circuit?

More on Transistors

Starting in the 1960s, a new term was heard in relation to radios, calculators, and televisions. I remember the commercial that inspired our family to get its first “transistor radio.” I also remember going to the Five and Dime or drug store to purchase a vacuum tube until we finally got that transistor television. Transistors replace those tubes by providing a semiconductor device having at least three legs: a source current terminal; a drain current terminal; and a gate terminal, which controls the output current.

• If the transistor gate is used to facilitate changes up and down in the voltage of the output, the transistor serves as an amplifier, something that can be used to control the volume of the transistor radio, for instance. As another example, consider the value of a transistor amplifier as LED dimmer!
• If the gate is used to control the “on/off” state of the circuit, the transistor serves as a switch. While our momentary switch circuits above required a physical act, the pushing of a button, a transistor switch uses an electrical input to determine the state of the circuit. Sometimes transistors do make use of some form of physical on/off switch or a momentary switch like the ones we’ve been using. At other times, the gate could use a microcontroller or microcomputer program to provide a digital on/off signal or analog low to high voltage signal.

A transistor switch is more straightforward and therefore a better demonstration for our purposes. Here’s an example of a 5V → 560 Ω resistor → 10mm green LED → N-type, or NPN, transistor circuit, in which a 3.3V momentary switch is used to temporarily pass the current through the transistor to ground.

If you glance at the schematic, there’s an arrow symbol at the drain terminal (also sometimes called the “emitter”) of the transistor. The N-type transistor is off unless the gate (also sometimes called the “base”) receives a small current, thereby completing, that is, closing the currently open circuit by passing ground to the cathode LED of the leg.

And here’s an example of a 5V → P-type, or PNP, transistor → 560 Ω resistor → 10mm red LED → GND circuit, in which the ground source also is sent through a momentary switch to another 560 Ω resistor to the PNP Transistor gate to temporarily turn on the current flow through the transistor, this time by temporarily grounding the base of the PNP transistor, creating a closed circuit by adding the current to the anode leg of the LED.

How might you add a NPN transistor remix into the Blue LED Circuit 2 above, the circuit in which the LED is continuously on unless the momentary switch is temporarily pressed?

As one last example, let’s replace the individual LEDs with an RGB (Red, Green, Blue) LED. These are constructed of three different types of crystals, one to make red light, another to make a green light, and a third to make a blue light. Technically, with the right setup we could see a million different colors. But as our electronic components and breadboard are currently configured to provide set voltages of 3.3V or 5V, our rainbow of colors is a bit more limited. Here’s a demonstration of a circuit with three transistor and momentary on switch pairings to provide seven different colors from a switching RGB LED circuit:

Do Something New!

For some, your lived experiences have helped you quickly move through the above exercises and review the associated key takeaways. Perhaps you’ve even repaired or built your own electronic circuits previously. If so, now might be a great time to try an Innovation-in-Use of the circuits we’ve already built to do the exercises above in a new way based on your own design inspirations.

Or maybe you’ve noticed some of the other electronic components included in your toolkit or that you personally have on hand that we haven’t made use of through the exercises in the first two sessions, items that you think would serve to take the circuit prototypes to a new level. Feel encouraged to consider entering into a collaboration with others to Remix through rapid prototyping on your breadboards!

Steps

In pairs, have one run through this test while the other observes. Then swap roles. Provide support to each other throughout, and make use of the videos as a guide.

1. Connect a black alligator clip to male jumper wire to the bottom blue rail of the breadboard. Connect a second alligator clip to male jumper wire (it can be any color of your choosing), to the bottom 3V3 red rail of the breadboard.
   
2. Carefully identify the + and the – symbols on each of the five Sequins.
3. Connect the black alligator clip (the one with the male jumper wire connected to the blue ground rail) to the – symbol on one of the five Sequins.
4. Connect the other alligator clip (the one with the male jumper wire connection to the 3.3 volt rail) to the + symbol of the chosen, grounded Sequin.
   
5. Carefully disconnect the 3.3 volt alligator clip from the Sequin to turn off the light, then disconnect the ground alligator clip from the Sequin. Then test the other four Sequins: connect the black ground alligator clip to a second Sequin, followed by the 3.3 volt alligator clip to that second Sequin. Repeat for the last two Sequins.
   
6. NOTE: If one of the Sequin Integrated Circuits burns out, and I’ve done that a time or two myself, consider fail-forward strategies for the person working hands-on with the electronics to improve their probability of “Yes” in their next lighting of a Sequin.

Key Takeaways

Each Sequin is an integrated circuit comprised of a resistor and an LED. These are incorporated onto a printed circuit board along with conducting material, such that when voltage and ground sources are applied to the + and – strips, the LED is lit.

Take a few minutes to watch this video demonstrating the steps to connect the Sequin Integrated Circuit and reviewing these components compared to other integrated circuits and electronic tools which use those parts.

NOTE: For those interested, there’s a side video showing the behind-the-scenes soldering of the Perma-Proto Breadboard creation shown in the video above:

• In the above schematic, how does the circuit using the Sequin integrated circuit compare with the three previous circuits we have constructed?
• How does the Sequin compare to other integrated circuit components, like the one integrated into a remote door opener as seen in the video?

Comprehension Check