Electrical Circuits featuring Snap Circuits 1-Way Switch Challenges – Level 2

1. Electrical Circuits featuring Snap Circuits 1-Way Switch Challenges – Level 2

2. Stop! Make sure you have completed the first PowerPoint: “Getting Started” before you continue with this PowerPoint!

3. What You’ll Learn… • How to control the flow of current in a circuit using four different types of 1-way switches • How to arrange multiple switches in a circuit to add decision-making intelligence • How to use truth tables to determine all the logical combinations that exist in a circuit containing multiple switches Different switches serve difference purposes

4. Rewrite and Answer these questions in your Word Document. • What is a Short circuit? • What are the most important type of flow control device in any circuit? • In very simplistic terms, computers are a complex system of what? • These systems are called logic gates and are the basic building blocks what? • What does CPU stand for and where do we find it? • In computer language, “on” and “off”, corresponds to what symbols and is called what kind of code? • What is an AND gate? • What is an OR gate? • What is the most common circuit used as a logic gate circuit? • How do you trigger a REED switch?

5. Caution! Safety first… Fortunately, none of the electronic components in your Tronix kit carry enough power to be dangerous. But that might not always be the case with electrical circuits you might encounter elsewhere. So when you are working with electricity, it’s always a good ideato develop safe work habits. • NEVER touch loose wires unless you are SURE they are disconnected from a power source. • ALWAYS make sure that power is switched OFF when making changes to an electrical circuit. • If in doubt, ask for HELP from a knowledgeable responsible person. Better safe than sorry!

6. Caution! Proper care of delicate electronic equipment… Some things you will work with in the SmartLab are STRONG and TOUGH. But electronic equipment is fragile and delicate by nature, because the wires are very small and easy to break. So how should you treat them? Electronic components are fragile, handle them with care!

7. Caution! How to avoid a short in your circuit… Short Circuit – a “short” in a circuit occurs when an alternate path (with less resistance) to the intended path is introduced. A path with no resistance allows too much current to flow. If the location of the short in a circuit only partially reduces resistance, it’s called a minor short. Minor shorts will typically disable a component in your circuit. If the location of a short eliminates all resistance, that’s called a dead short. Circuits with a dead short quickly melt or burn something up! The electrical opposite of a short circuit is an "open circuit", which happens when a wire is broken or missing so that no current can flow. Open circuits cannot operate but they do not damage anything like a short circuit does. Shorts usually occur when someone puts an extrawire in the circuit. Red wires should NOT be there because they cause a short circuit. Dead Short Minor Short A minor short just disables one component, but a dead shortburnssomething up!

8. What You Should Know… Electricity basics… You should already be familiar with the Snap Circuits kit. You should also already know the basics of electricity, including what it is and how it is created, the different types, how it is measured and the basic elements of circuits. If you are not familiar with any of these concepts, you should review the What You Should Know section of the Level 1 – Getting Started with Electricity Learning Launcher.

9. What You Should Know… Using 1-way switches as flow control devices… Do you remember the four basic elements common to all circuits? Here’s a quick review! Switches are the most important type of flow control device in any circuit. They enable you to turn things ON and OFF. Your Snap Circuits kit has two different general categories of switches: 1-way switches, and 2-way switches. This Learning Launcher will focus on the 1-way switches. The two different 1-Way switches in your kit are designed to turn things ON or OFF. That’s all they do, but they do it in different ways depending on the type of switch. Let’s explore each type of 1-way switch by using them in simple circuits. • Energy Source • Path • Flow Control • Load Push Button Switch Slide Switch

10. What You Should Know… Logic Gates in Computers… In very simplistic terms, computers are a complex system of on and off switches. In computer language, “on” and “off”, corresponds to 1’s and 0’s; this is called binary code. In order for computers to deal with complex information, they require a VERY complex system of switches. The number of switches and the way they are arranged allows computers to store and process complex information. These systems are called logic gates and are the basic building blocks of digital circuits. In this Learning Launcher, we will explore two kinds of logic gates: “AND” gates and “OR” gates.

11. Warning!

12. Do It! Using 1-way switches as flow control devices… Start by building the circuit you see here, and press the button to turn the light ON. Notice that the light is only ON when you are holding the button down. As soon as you let go of the button it springs back up to turn the light back OFF. This type of switch is called a momentary switch. It is only on for the moment that you are pressing the button. Push Button Switch

13. Do It! Using 1-way switches as flow control devices… Replace the Simple Switch with the Slide Switch. Switch it back and forth. Is this switch a momentary switch? No, because it stays on or off when you switch it and let go. Most light switches in your house are like the Slide Switch. Look up what a Magnetic Reed Switch. What is it? How does it work? What could it be used for?

14. Security Security Do It! Practical applications for 1-way switches… Now that you’ve experimented with each of the different 1-way switches in your kit, make a list of a few practical applications for each different type of switch. Push Button Switch Slide Switch Magnetic Reed Switch Momentary Switches

15. B A Do It! Adding intelligence by adding switches… Did you know that the CPU (central processing unit) in your computer is loaded with millions of microscopic switches calledlogic gates? These logic gate switches enable the computer to make millions of decisions. You can get a feel for this concept by building your own intelligent circuits starting with the AND gate. Build this AND gate circuit using the schematic below as your guide. “AND” Gate

16. Switches Light A B B A OFF OFF OFF OFF ON OFF OFF OFF ON ON ON ON Do It! AND gates require two true inputs to work… What did you have to do in order to make the light turn ON? You had to turn BOTH switches ON, right? How many switching combinations could you have tried that would NOT light the bulb? Look at the chart below to answer this question. Since you have two switches, and each switch can be in two different positions (ON or OFF), you have 2 x 2 = 4 different unique switching combinations. But only the last one on the chart results in the light being ON. This chart that shows all the switch combinations is called a truth table. “AND” Gate

17. Do It! Designing the OR gate circuit… You discovered that the AND gate requires two conditions to be true. It’s like saying, “If I get an “A”and my parents increase my allowance, then I will be able to afford that new guitar”. With this AND statement, only one combination results in you with a new guitar. The OR statement is a little bit different. Build this OR gate circuit and then experiment with all the possible switch combinations to see how many ways you can make the light turn ON. A “OR” Gate B

18. Switches A Light A B OFF OFF OFF ON OFF ON ON OFF ON ON ON ON Do It! OR gates are much easier to please… How many different switch combinations did you try? Hopefully it was four because that’s the maximum possible. Remember that you still have two switches, and each switch can be in two different positions (ON or OFF). So you have 2 x 2 = 4 different unique switching combinations. How many of the switch combinations resulted in the light being ON?The truth table below shows that the OR gate isn’t as picky as the AND gate. The OR gate will power the light every time at least one of the switches is on. The OR gate turns the light ON any time the AorB switch is on. B “OR” Gate

19. Switches Light Switches Light A B A B False False False OFF OFF OFF True False True OFF ON OFF True False True OFF OFF ON True True True ON ON ON Do It! Why they call the chart a truth table… Have you ever noticed that some switches have a “1” and a “0” printed on the switch? The “1” means ON, and the “0” means OFF. Mathematicians and scientists often use the words “true” and “false” to mean essentially the same thing. So in the world of logic; True = 1 = ON, and False = 0 = OFF. We have three different ways to say or represent the same basic thing. If we use the word TRUE in the place of ON, and the word FALSE in the place of OFF, we turn an ON – OFFchart into a TRUTH TABLE, and that’s the terminology everyone uses. The ISC power switch AND Gate Truth Table OR Gate Truth Table

20. A B AND Gate A B A A B OR Gate B Do It! 7 Logic Gates: The building blocks of computer intelligence… There are seven different logic gates in all, but for now we are only exploring the ANDandORgates, which you just experimented with. Before we continue, let’s review the AND and OR gates. On the left you see the schematic symbol used in electrical diagrams to represent each gate. In the center you see the circuit that the symbol represents, and on the right a short description of how each logic gate works. Next we’ll give you some more practice. Building the additional practice circuits that follow will make this a lot easier to remember and understand. Two switches must be closed (ON) for the light to work. AND Gate Logic gate symbols used in schematic diagrams Only one switch must be closed (ON) for the light to work. OR Gate

21. Do It! Which logic gate would you use? You probably have a doorbell at your front door. Let’s say you wanted to add a button at the back door that would ring the same bell if someone pushed it. Would this circuit be an AND gate or an OR gate? What if you had a potentially dangerous machine – like a car crusher. You wanted to install a circuit that required TWO buttons to be pushed at once so it wouldn’t go on if someone accidentally pushed one of the buttons. How about this circuit - would it be an AND gate or an OR gate?

22. Switches Light A B A ON ON ON OFF ON OFF OFF OFF B Do It! Which logic gate does this circuit make? Now that you’ve had an initial experience with the AND and OR gate circuits, see if you can tell which logic gate this circuit creates. Build and test this circuit and create a truth table to document what it does. The results of your test should tell you whether this is an AND gate or the OR gate. “?” Gate