Background Knowledge Probe

Write a list of the electronics that you make use of on a regular basis.

• Who comes to mind as the designers of these?
• What parts, inside and outside the hood, were used to build each one? To use it?
• What have you done with any items that started to work less than optimally?

Example: A Single LED Circuit

An electrical circuit is a path in which electrons flow from source to ground. The source is usually measured in voltage (the force, expressed in volts) or current (the flow, expressed in amps). A resistor (expressed in ohms) controls the flow of this source.

When I water my garden from a rain barrel, a full barrel has more pressure than one that is almost empty. That full barrel is the equivalent of a higher voltage power source, for instance, one that is 240 volts. A barrel two-thirds of the way full may be more like a 120 volt power source, while a nearly empty rain barrel may be closer to a 5 volt power source.

If I have a spray nozzle hooked up to my rain barrel, I can often use a lever to increase or decrease the water’s flow. This is equivalent to the current of the power source. Some of my water hoses are 1/2″ thick, while some are 3/4″ thick. This is equivalent to bigger or smaller ohms of a resistor, respectively, since a thinner hose increases the resistance of the flow of water compared to the thicker hose.

As a side note, in electrical engineering, Ohm's Law provides a basic equation I=V/R. This states that current (I) is equal to voltage (V) divided by resistance (R). And as all Trekkies know from their days with Jean-Luc Picard, resistance is not futile, it’s essential! Beyond this, don’t worry if you are ready to put aside these particular details.

Schematics are commonly used to draw out the path used by the electronic components to complete a circuit.

As an example, the Fritzing image above is a schematic with three electronic components:

• a battery
• a resistor
• a light emitting diode (LED)

The lines between are not electronic components, but rather are some form of conductive material like a metal wire that is used to carry the current from component to component. In the schematic, a positive current leaves the 9 volt battery and passes through a 560 ohm resistor before connecting to the positive charge of a 10mm white LED. From there, it passes through the negatively charged leg of the LED to the ground connection of the 9 volt battery, completing the circuit. Only when this circuit is fully and properly completed and the battery has sufficient charge to dispatch a current will the LED turn on. (Schematics and breadboard diagrams in this book were primarily created using the open source program Fritzing.)^[1]

Schematics don’t tell us anything about how the circuit is actually built, and indeed the visuals for the different components needed are confusing artwork until their interpretation is provided. But with a little bit of practice, schematics become a unique conceptual information source. We can use design thinking and rapid prototyping to physically make the circuit using specific parts on hand or acquired to achieve something we value, even if it’s just good enough to help more than bother us.

Often times, when you look for a plan or pattern to use electronics to perform a certain task, instead of a schematic, you’ll find a physical diagram of the parts as demonstrated in the Fritzing image shown above. This diagram is based on someone’s layout choices using available components to actually implement the circuit drawn in the Fritzing schematic at the start of this example. In the physical diagram, we see electrical components connected using a solderless breadboard, a plastic board with conductive clips under groupings of plastic holes, thereby allowing the passage of current between components.

At the left of this particular diagram, a red wire brings the positive current of the battery to the lower red rail of the breadboard. Another red wire moves it from this rail to row J, column 59. Row H, column 59 then connects the current to one leg of a 470 ohm resistor, which carries that current, now under resistance, to row H, column 55. This brings the current to the positive charge of a 10mm white LED. Row E, column 55 is connected to the negatively charged leg of the LED, which then passes to row A, column 55 where it is connected to a black wire that carries the current to the upper blue rail on the breadboard. A black wire then brings the current to the ground connection of the 9 volt battery, completing the circuit.

As you move forward, you may find yourself exploring and evaluating a variety of online guides, resources, and examples and comparing them to what is shown in the book. (Indeed, take a deep dive through the many examples found at Adafruit Learning System, from which we draw many for this book, for an extraordinarily wide range of electronic systems, along with supporting code.) Sometimes you may find schematics. But more often you’ll find diagrams illustrating how someone or a group have put the circuit into practice. Know that diagrams may be rigid as they tend to focus on a specific task in a specific configuration in a specific environment that suits a specific cohort, community, or culture. Schematics, on the other hand, are found in more professional settings and as such can be applied to a greater range of applications. These schematics, after doing research to define the components illustrated using specific visualizations, will also prove very helpful for problem solving or rapid prototyping for all innovators, regardless of experience.

It may be helpful to think of schematics as standards used for many different applications, projects, and occupations. Schematic drawings are relevant for many users from electrical engineers to K-12 students. For example, circuits and schematics are part of the Next Generation Science Standards (NGSS) Energy Unit for elementary school students in grade 4.^[2]

Underneath the Hood of the Breadboard

A solderless breadboard is a plastic board used to create models or prototypes of an electric circuit. They’re solderless because you can easily push wires into the provided holes and later pull them out to move them into new configurations. They come in different shapes and sizes. The most commonly used “full sized” breadboard is 6 1/2″ long and 2 1/8″ wide.

Below, you’ll note several different images of a full sized breadboard. In the first image, you see the typical working view of the breadboard.

In the next image, we see the bottom side of a breadboard. The left half of the center image has the sticky covering revealed, while the right half has the protective covering installed. If the breadboard is moved around a table or desk, a protective covering remains on the underside of the breadboard (seen in the right half of the center breadboard). You can remove that covering to enable the breadboard to stick to a surface (seen in the left half of the center breadboard).

In the breadboard image below, we see the underside of a breadboard, but this time with the sticky tape fully removed. Breadboards typically come with rails along the edges, with conductive metal clips (two of which are shown at the very bottom of the image) installed so as to carry the flow of current along the extent of each rail.

If you compare this image of the breadboard metal clips to the image of the top side of a breadboard, you’ll note there’s a red colored rail and a blue colored rail on the upper part, and another red rail and blue rail on the lower part of the breadboard. The red rail is typically used to carry a positive source to a circuit or series of circuits, while the blue rail is typically used to carry the circuit or series of circuits to ground. The main part of the breadboard connects together groupings of five holes using 126 conductive metal clips.

Thus, column 1, row A is connected to rows B, C, D, and E of column 1 with one metal clip. Column 1, rows F, G, H, I, and J are interconnected with a second metal clip. Column 1, rows A, B, C, D, and E do NOT connect with column 1, rows F, G, H, I, and J by default. They will only interconnect if a wire or electronic component is plugged into one of the left holes of column 1 and also to one of the right holes of column 1, and is set to pass a current from one connection to the other.

Exercise: Building and Testing an Electronics Prototyping Platform

In the previous example, a circuit was created using a 9V battery, as shown in both a schematic and a diagram. Throughout the rest of this book, we will typically not use a battery to power our electronics. We’ll start by using the USB to TTL cable that comes with the toolkit, allowing us to connect the USB side to a 5-volt power source. The 5-volt power source itself is likely connected to either a 120- or 240-volt power alternating current (AC) source, which it inverts to 5-volt direct current (DC) power. The TTL side of the cable will only be used for now to provide power through the red cable and ground through the black cable. Later in the book, we’ll also use the white transmit cable and green receive cable to facilitate data communications between devices.

The image above provides a diagram of the basic configuration of our prototyping breadboard, in which power is provided using a USB to TTL cable from the toolkit. The basic circuit located on the breadboard illustrates how 5 volts of current pass through conductive material from the USB to TTL cable, conductive material within the breadboard, and jumper wires to an electronic component called an LED, before returning through additional resistors to ground, thereby completing the circuit.

In the above diagram, it is important to note that the only electronic components are the 470 Ω (ohm) resistors and the Red/Green/Blue (RGB tricolor) LED. The breadboard, jumper wires, and USB to TTL cable are not electronic components, but rather are forms of conductive material used to carry the current from component to component.

Another way to illustrate a circuit is with the schematic below, helping to visualize the single physical LED as three separate functional LED chips incorporated into a single package. Each of the three LED chips are themselves small semiconductive materials in which a Light Emitting Diode electronic component can be embedded.

In the schematic, there are several standard symbols used:

• The United States standard symbol for a resistor;
• The symbol for a light emitting diode;
• The symbol for a connecting lead;
• The symbol for a junction of conductors; and
• The symbol for an integrated circuit.

For some, such as an integrated circuit (IC) schematic, IC subcategories are further developed for the specific specialty component being used, as is the case for the USB-TTL Cable from Adafruit.com. Inside the blue USB plug case is a USB↔Serial conversion chip that can work with drivers to provide Universal Asynchronous Transmit Receive (UART) communications which we’ll start using in this exercise.

Together, these standard symbols are a helpful way to view both diagrams and schematics when starting a new electronics project.

In the above figure, you’ll see a range of symbols commonly found within schematics and diagrams. Note that in this chart, the resistor schematic is a bit different from the one found within the Fritzing schematic for this exercise, as the Lumen Learning modules use the European standard. The Fritzing diagram uses the symbols common within the United States. While most are the same, a few, like resistors, do differ^[3].

For the breadboard exercises in the book, we will be using a RGB (red/green/blue) LED. This three-in-one LED makes use of one leg that can either be the common anode with a shared power source for the RGB legs, or the common cathode leg with a shared ground source for the three LEDs.

For exercises throughout this book, we are using the diffused RGB (tri-color) 10mm LED with common anode from Adafruit. The anode (longest) leg can accept up to a 5-volt power source. The anode leg then connects to each of the red, green, and blue LED “chips” (“chip” is another term for an integrated circuit). Each chip connects to its own metal wire, which serves as the cathode leg for that LED. For exercises within this book, we then individually return each chip to ground in parallel through three resistors.

In the image above, you will find the shorter red cathode metal leg at the top, then the long anode metal leg, the middle-length green cathode metal leg, and finally the short blue cathode metal leg at the bottom of the image.

Troubleshooting Essentials

Collective leadership and community inquiry using groups of two or three people to collaboratively test out hands-on work brings together the expertise of multiple individuals.. Failure is common, and generally remains the norm, from iteration to iteration for an extended period.

To positively fail forward, our iterations are an opportunity for us to discover how our inspirations and ideations aren’t aligning with our past and current iteration prototype. Reflecting on our actions individually and as part of community inquiry is central to that work of discovery. Said another way, iterations help us see how one part, much, or all of our working idea is falling short of good enough. This helps inspire better ideations and sometimes even new inspirations, ultimately leading to better iterations — at least for us within the given testing context.

Let me say this again: Trying and failing is not optional. It is the norm. The general alternative to failing forward is failing to improve.

Accepting failure as a normal, active, ongoing part of what we do leads us to failing forward in ways that facilitate growth and betterment of ourselves, and when done across functional diversities and community cultural wealth, the betterment of others as well. In so doing, we foster a high performing community of practice.

So let’s assume the LED did not light up in the last exercise, or that it burned up in the last exercise, or that it won’t light up in the next exercise. Why not? What happened?

Humans and other more-than-human persons around us have a rich range of analog senses, such as sight, hearing, feeling, and smelling. These are a wonderful resource in the troubleshooting process. These analog senses provide a continuously variable physical quantity, such as the visible wavelengths of light. This stands in contrast to the digits 0 and 1 that typically represent the values of a physical quality provided by digital measurements.

Bringing our observations through those analog, continuously variable, senses into a process of critical thinking helps us create a plan for testing out a range of possibilities. Enacting that plan one step at a time helps us to continue the cycle of observation, thinking, planning, and acting. This is the heart and soul of inquiry-based learning as we collaborate in pairs and small groups through dialogue.

Throughout the remainder of the exercises in this book, and as you work through your own design activities putting your learning into practice, be sure to make extensive, preferably documented, use of these troubleshooting basics. It’s tempting to try it a few times and move on because troubleshooting the current exercises begins to become second nature. These experiences serve as a learning opportunity, but at the risk of having the learning become hidden knowledge that fails to fully help you as you encounter future problems.

Indeed, this is a reason why this book has been written using the Creative Commons Attribution-ShareAlike license. We hope you will add in annotations, page notes, and remixes for yourself and others to use as sources for their own design thinking projects. We hope the resulting inspirations, ideations, iterations, and failures support an advancing betterment of ourselves, those in our community of practice, and those we are serving through our creative works.

Exercise: Adding a Two-position Switch to Our Circuit

In this activity, we will add a slide switch into our circuit. It is called a “switch” because it changes the flow of current depending on the state of the switch. This switch creates a change in state when a physical action happens—in this case, when a slider is moved to the left or to the right. This type of single pole, double throw (SPDT) switch is a great electronic component to turn something on and off, or to select between this or that. The center pin provides the rest of the circuit with the results of the user’s choice. The left and right throw pins provide the user with one of two options. We’ll be using this switch in a variety of ways moving forward. For now, we’ll connect the single center pole to the RGB LED, and the right pole to the lower red rail providing a 5-volt power source. The left pole will be left open. The user then chooses between providing the RGB LED with 5 volts of power (on state) or no power (off state). When the slide is to the left, we have a closed circuit because the switch creates a state in which power completes circle over to ground is complete. When the slide is to the right, we have an open circuit because there is no starting power needed to begin the flow of current required for a completed circuit.

Voltage, Resistance, and LED Brightness

Earlier in this chapter, we covered a bit on Ohm's law, which provides a basic equation I=V/R stating that current (I) is equal to voltage (V) divided by resistance (R). Voltage is like the pressure of water in a hose. Current, measured in amperage, or amps for short, is like the flow of water through a hose. The thickness of the hose impacts the resistance of the flow of water through it, which is like the ohms of resistance in a circuit.

Let’s take the water analogy one step further. Imagine the water is now used to turn a wheel, which is used to power a small mill making gristmill, which is used to turn cereal grain into flour. You can increase the power generated by the water wheel by either increasing the pressure (voltage) of the water or increasing the flow (amps) of the water. In electrical terms, this power (P) is called wattage, or watts.

The formula for this is Volts x Amps = Watts.

Some may be familiar with, and perhaps make regular use of, lighting in which you can control the brightness of the light. Perhaps you have a lamp with a three-way light bulb providing three different watts of power, depending on the position of a rotary switch. Each turn of the light switch steps you up to the next wattage before returning to off. The lightbulb may state that it is a 60/120/180-watt bulb. If you are in the United States, you likely plug this lamp into a 120-volt outlet. We now are using one of three amps of current

• 60 watts / 120 volts = 0.5 amps
• 120 watts / 120 volts = 1.0 amps
• 180 watts / 120 volts = 1.5 amps

If our 120-volt outlet is listed as being a 15-amp circuit, we should keep in mind that if all these lamps were running at full wattage, we should have a maximum of 15 amps / 1.5 amps = 10 lights at 180 watts.

Let’s look back at our RGB LED. It is rated for a maximum of 5 volts. Adafruit has a USB 2.0 Powered Hub with 7 ports, each with 5 volts at 2 amps. If we were using this for our RGB LED, the common anode would be receiving

5 volts x 2 amps = 10 watts of power

But given we have a 470 Ω resistor wired to each cathode leg to assure it doesn’t get so much current that it burns out, each of the parallel circuits is reduced a bit, as we see in Ohm’s law (I=V/R):

5 volts / 470 ohms = .01 amps
5 volts x .01 amps = .05 watts

To demonstrate, four parallel LED circuits have been created, each receiving different amps of power, thereby providing different watts of light. The breadboard circuits use the following components:

• A USB to TTL connected to a USB 2 powered hub providing 5 volts at 2 amps. This is attached to a full-sized breadboard as before.
• A voltage regulator, an electronic component that brings the voltage of a power supply down to a level compatible with the other electronic components. Here a voltage regulator is being used that can work with 4-20 volts of DC power as the source (in our case, 5 volts at 2 amps), which it then regulates down to a stable 3.3 volts DC power.
• Two 470 Ω and two 10,000 Ω resistors
• Four 10mm bright white LEDs

From left to right, the watts of power of each LED in the image above are as follows:

These are clearly not nearly as bright as a 60-watt light bulb in a house! But as the plastic cases of each of these bright white LEDs are not diffused like the diffused RGB LEDs we’ve been using, we can see how much more they brighten the view of the breadboard, especially the 1/20th of a watt from the 5V + 470 Ω LED circuit.

Do Something New!

For some, this is your first journey into electronic circuits. You’re Doing Something New through troubleshooting electronic circuits and failing forward! You are at a “yet-enough” point to head on down to the Wrap Up and Comprehension Check at the bottom of this chapter.

For others, you may already have a lived experience with electronic circuits. This is not something new to you. But if you’re at all like me, some of this work has become rote, and the underlying terms, concepts, and principles hidden knowledge. For you, Doing Something New may be a work of re-remembering the codes to the electronic wheelhouse. And moving beyond, maybe it’s discovering some of the social influences that have shaped the non-neutral aspects of the otherwise strict laws of physics within.

For all, it’s likely that at least some aspects of Collective Leadership, Community Inquiry, Action-Reflection, the Information Search Process, and Pair/Triplet Programming are new to you. Do Something New! by incorporating one or two of these into your work, this and every session, individually and as part of your Community of Practice work.

Below are two Do Something New! exercises putting the above brightness display into practice using your own starting breadboard circuit prototype, this time using the RGB LED. How much do they change the brightness of red, green, and blue diffused LEDs? For those not yet ready to take on the exercises but still wanting to dig a bit more into what’s behind the hood, you can also skim one or both activities themselves and then delve more into the Key Takeaways of each to advance from understanding less to understanding more.

Exercise: Using a Switch to Compare Differences in Resistance of Current Flow

In setting up our parallel red, green, and blue RGB LED circuits, each cathode leg is passed through a 470-ohm resistor on the way to ground. The change in amps remains the same whether the resistor is placed before or after LED within a circuit, in this case 5V/470 Ω = 0.01064 amps (10.64 milliAmps or mA). The switch is currently used to select between “on,” in which case 10.64 mA sent to the common anode leg of the RGB LED, or “off,” in which case no current is sent to the RGB LED.

In this Do Something New! activity, we’ll add a new 470 Ω resistor to the left throw pin of the slide switch. This resistance will be added to each of the three cathode legs so that all three LEDs now pass through 940 ohms of resistance. Using Ohm’s law, 5V/940 Ω = 5.32 mA, or half the 10.64 mA sent to the common anode leg when the slide switch is to the right.

Steps

1. Tightly bend down 90 degrees the two legs of a fourth 470 Ω resistor.
2. Insert one leg of the resistor in column 30, row H, and the other in column 26, row H.
3. Connect one end of a male/male jumper wire to column 30, row E, and the other end to column 30, row F. Now current from the red power rail is passed to rows A-E of column 30, the jumper wire attached in step 1, and to rows F-J using a second jumper wire we just installed as part of step 2.
4. Connect one end of another male/male jumper wire to column 26, row F, and the other end to column 28, row E. This is the left selection leg of the slide switch.
5. Finally, make sure the TTL to USB is plugged into a power source. Then slide the switch left to examine the brightness of the RGB LEDs when the current passes through an additional 470 ohms of resistance before entering the shared anode leg of the RGB LED. Compare this to the brightness of the RGB LEDs when current enters directly to the shared anode leg of the RGB LED.
   • This change will impact the red, green, and blue LEDs differently, as each of these light-emitting diodes work within different ranges. Plus, red alone is different than red plus green, which is different from red plus green plus blue. Try different combinations of red, green, and blue circuits connected to ground to fully test the differences.
   • If you can, take pictures of the RGB LED circuit with the switch to the left and to the right so that you can more readily compare the differences between them.

Below, you can see the schematic of our new circuit, which you can compare to the Fritzing diagram above. Looking at the standard switch symbol used in the schematic drawing, we see that what passes from leg 2 over to the common anode leg of the RGB LED is determined by the line that rocks between legs 1 and 3 of the switch. In designing this circuit, I chose to connect the 5-volt current directly to leg 1, and to run the 5-volt current through a 470 Ω resistor before connecting to leg 3.

Let’s further compare our switched resistance schematic above with the schematic from the first exercise, in which the 5-volt current was connected directly to the common anode leg of the RGB LED. Note that while initially 5 volts flowed directly from the USB to TTL cable to the common anode leg of the RGB LED, it now first flows through a slide switch, in which it either passes directly to the common anode leg or passes first through an additional 470 Ω resistor before reaching the common anode leg.

Key Takeaways

Resistance is a common way to control the brightness of lights. In our breadboard prototype, resistance changes the flow of current from source into the common anode leg of the RGB LED, and out to ground by way of the red, green, and blue cathode legs. We have already included 470-ohm resistors in our red, green, and blue circuits, to assure that the flow of current when connected to a 9-volt battery does not exceed the amount of current listed within the current rating of the RGB LED we’re using. (This is a general introduction—for more on current ratings of LEDs and how to use this to select power sources and a resistor for a circuit, I highly recommend “All About LEDs” by Tyler Cooper.) While it is essential that you include at least the minimum required resistors within your circuit, resistors are often used to intentionally restrict the flow of current further than required, as a way to control the brightness of light provided.

The flow of current can be controlled using many different types of switches. You might have lights at home that can be dimmed. Your mobile phone might let you use a slide to control its brightness. Or you might be able to enable or disable “nighttime mode” for your clock. When a circuit is designed to provide a steady gradation in resistance, the type of electronic switch commonly used is called a variable resistance potentiometer. Potentiometers slowly change the level of resistance provided from a defined minimum (e.g., 470 ohm) to a defined maximum (e.g., 10K ohm). Below are Fritzing images of a 10K potentiometer that could be used for our testing.

For this exercise, we used an electronic single pole double throw (SPDT) slide switch. The single common pole in our exercise is used to connect to the common anode leg of the RGB LED. The two throw legs are then connected directly to a 5-volt power source and to a 5-volt current that is first passed through a 470-ohm resistor. Selecting one of the two throw legs of the switch chooses whether to provide current directly from the rail or via a resistor. The slide switch was selected as a simple means for comparing two different conditions—this one or that one. In the above, we used it first to choose between off and on. Then we chose between a direct 5-volt connection and a 5-volt connection with 470-ohm resistance. And next we’ll use it to choose between different voltages.

• How does the brightness of the light from the RGB LED—either together or in different combinations or red, green, and blue—change when the slide switch is moved left or right? Why, and how much?
• What are some reasons you can think of that I decided to design the selection and use of the LEDs, resistors, switches, and wires in the way that I did to set up your execution of this activity?
• What are some ways we might have done it differently, and in so doing may have created a better way for you to complete this activity?

Exercise: Using a Switch to Compare Differences in Voltage

For this second Do Something New! activity, let’s use the two-way switch to select between a 5-volt and a 3.3-volt current, to consider how a difference in the voltage of current compares to a difference in the resistance—that is, the flow of current. Today’s USB standard works with 5-volt direct current (DC). Most homes and offices have wall outlets that use 120V or 240V alternating current (AC). A power converter is used to switch from alternating to direct current. 5-volt DC has proved a solid choice for many electronic circuits, but others, like fans and motors, often make use of the widely used 12-volt direct current. And some electronics have worked to reduce power usage by going the other direction, decreasing current to 3.3 volts. Unlike the AC voltage standards used within different countries, the 3.3V, 5V, and 12V DC are not standards, just widely used voltages. When selecting electronic components, it’s important to identify the range of voltages which can be used for that component and to plan accordingly.

The RGB LED we’re using has a maximum forward current rating of 20 milliamps (mA). Looking back at the start of this chapter, we saw a demonstration of a circuit built using a 9-volt battery and a 470 ohm resistor. Together, 9 volts at 470 ohm is 19 mA, just under the 20-mA maximum current rating of many of the LEDs we use today. Using a 5-volt power source, we could have safely gone down to a 100 ohm resistor, but stayed with the 470 ohm resistor in case a 9-volt battery was used instead of a 5-volt USB power source. Together, 5 volts at 470 ohm is 10.6 mA. If we go the other direction, down to 3.3 volts at 470 ohm, we are now at 7 mA, or 1/3rd of the amperage used with 9-volt power and 2/3rd the amperage used with the 5-volt power.

Keeping resistance constant, how does decreasing current usage by decreasing power impact the brightness of an LED? Let’s find out by using a voltage regulator. A voltage regulator is useful when you have a possible range of voltages for a power source, but are needing a stable voltage for your electronics. Look at your laptop power adaptor, and it will likely say it can work within the range of 110V to 240V AC input. It will also list a stable DC output voltage or voltages to be provided regardless of the input voltage.

In our case, we’ll use a voltage regulator that can work with 4-20 volts of DC power as the source, which it then regulates down to a stable 3.3 volts of DC power. To keep this simple, we’ll replace the 10k ohm resistor with the voltage regulator. But this could be connected to its own switch that then feeds into the slide switch used for the resistor to do a 2×2 comparison of resistance and voltage on LED brightness. And as an important side note, the GPIO pins of a Raspberry Pi we’ll be using in session four of the Orange Unit provide both pins with 5-volt power, which they receive from the micro-USB or USB-C plugin and pins with voltage regulated 3.3-volt power, allowing us to bring both to the breadboard for ongoing use. This Do Something New! provides a first glimpse at some possibilities for if we were connected to the Raspberry Pi GPIO instead of the USB to TTL cable for breadboard power and ground.

Steps

1. Return to the on/off switch circuit for the RGB LED
   • Remove the 470 Ω resistor and associated jumper wires.
2. Connect an LD33V voltage regulator such that the LD33V label is facing the switch.
3. Use jumper wires to provide the ground and 5V power sources to the regulator, and connect the regulator output to the left throw leg of the switch.
4. Finally, make sure the TTL to USB is plugged into a power source. Then slide the switch left to examine the brightness of the RGB LEDs when 3.3 volts of power are provided, compared to when the switch is to the right and 5 volts of power are provided.
   • If you can, take pictures of the RGB LED circuit with the switch to the left and to the right so that you can more readily compare the differences between these.

Key Takeaways

This layout of the breadboard now provides an opportunity to compare brightness depending on voltage. For this exercise, we incorporated another commonly used electronic component, known as a voltage regulator, to take the 5 volts of power provided through the USB to TTL cable and regulate it down to a stable 3.3 volts of DC power. As we’ve now seen in these two Do Something New! activities, there are two ways to adjust the brightness of an LED: by changing resistance and by changing voltage.

1. Of these different layouts, how does voltage change brightness when all else is equal? How does this compare to the brightness when the 5-volt power remains consistent and resistance is changed, as was done in the second exercise?
2. What are some key takeaways regarding the brightness of LEDs, given the combined factors of different power sources and resistance levels?

Wrap Up

This is just a first glimpse at electronic circuits and some ways we can work hands-on in design and prototyping of new circuits. We’ve learned a few basics of creating a completed circuit and how to troubleshoot when the circuit doesn’t seem be working. We’ve learned out to use components to switch the circuit from complete (on) to incomplete (off), and how to switch between levels of resistance and voltage to change the brightness of an LED. Along the way, we’ve started discovering there are many choices to be made. For instance, both resistance and voltage can be used to control the brightness of a light. But while batteries and AC outlets generate power for use by electronics, resistors and LEDs make use as Tyler Cooper notes near the end of “All About LEDs.” Use the lowest voltage possible to get a sufficiently bright LED. But beyond that, switching between voltages can become laborious if you need to regularly change brightness. That’s when resistors especially come into play. On the other hand, too often we continue make use of resistors and voltage regulators to stay with the same large power generators we’ve always used when more environmentally friendly low power sources could be used if this is kept in mind during design.

And so there have also been some question prompts urging you to question the reasoning behind the design of the circuits themselves. Accomplishing an electronics goal can be achieved using many different components and circuit designs. Helping others to build, make use of, and further innovate electronics is yet another place allowing for extensive variations. It’s important we keep front and center these extended question prompts if we are to rapidly shift from a thing- to a person-orientation as we work to demystify technology.

There’s much more to come as we proceed through the Orange Unit and beyond. For now, take a few minutes to do a quick comprehension check on some of the key circuit terms and concepts we’ve used so far.