You are required to lead a lab activity with the class
Template for Computational Science Related Lessons
Title of Lesson: Electrical Engineering and Circuits
Grade level / course: Middle School
|Objectives / Concepts |
|Lesson Abstract: |
|Learning about more complex circuits, including using capacitors and Integrated Chips to build a circuit |
| |
|Standards Addressed: |
| |
|Objectives: |
|Students will understand the concept of a capacitor and how its size affects how it performs |
|Students will be introduced to a Integrated Circuit (IC) chip, the 555 Timer |
|Students will be able to build a circuit using the 555 Timer which makes a LED blink |
|Students will understand how to change the speed at which the LED blinks using the capacitor |
|Prerequisite knowledge: |
|Students should have learned about basic circuit elements including |
|Batteries |
|Wires |
|Resistors |
|LEDs |
|Breadboards |
|Ideally the Students learned about all these things through an analogy with a water wheel |
|Students should have built a simple circuit with battery, resistor, and LED on breadboard |
|Teacher preparation: |
|Assemble bags and breadboards with all necessary components |
|Explore the applet site to help students find the right example circuits |
|Required Materials |Media (software, websites, overhead, |Equipment (computer, display, OHP, VCR, |
|(What and how much) |transparencies, video, etc) |etc) |
|Circuit Components (for each student) |Falstad circuit simulator |computers |
|1 x Breadboard | |projector |
|1 x LED | | |
|1 x 555 Timer | | |
|1 x 10 (F Capacitor | | |
|1x 100 (F Capacitor | | |
|3x 10 k( Resistors | | |
|1x short (5 cm) red wire | | |
|1x short black wire | | |
|1x short blue wire | | |
|1x 9V battery | | |
|1x 9V battery leads | | |
|Circuit Diagram Layouts | | |
|Safety (Precautions and reminders) |
|Do not work on the circuit with the battery connected for safety of the circuit and the builder |
|Be careful of polarity with capacitors and LEDs and with the connections to the 555 timer. All of these components are damaged by |
|incorrect polarity or high currents and can smoke, or get very hot. |
| |
|Presentation Outline |
|Time | Event |
| | |
|Introduction/ Review |You just learned about several different components of a circuit and built a simple circuit yourself. |
| |Lets go over the different components we used. |
| | |
| |Ask the student which components they used and what each component corresponded to in the water wheel |
| |analogy (if the analogy was used). |
|5 min | |
| |Should Recall: |
| |Breadboard is like the landscape |
| |Battery is like the Hill |
| |Wires are like the pipes or channels |
| |Light bulb/LED is like the water wheel |
| |Introduce a new circuit element, the capacitor. |
| | |
|Capacitor |Explain that the capacitor is like a water tank of glass |
| |As water comes in the tank fills up |
| |The faster the water comes in the quicker it fills up |
| |Can only fill to a certain point |
| |A larger (wider) tank fills up more slowly than a narrow |
|10 min |Likewise for a capacitor: |
| |Current flows in and fills the capacitor, raising the voltage of the capacitor |
| |It fill up faster with higher currents |
| |Only will fill up to the supplied voltage |
| |Larger capacitors take longer to charge |
| |Show the circuit diagram representation of the capacitor |
| |Be sure to emphasize the polarity of the capacitor and how the long lead is the positive one. Have |
| |students look at the markings themselves. |
| |Next Introduce the 555 timer |
| |Explain how it is an Integrated Chip or just a chip, which is very complicated on the inside. |
| | |
|555 Timer |It is used for timing in many things because it turns things on and off at certain times: |
| |Examples : Car windshield wipers, interior lights, etc |
|10 min | |
| |The chip is controlled by the voltage on the capacitor. When the voltage is high, the output is off; |
| |when the voltage goes lower, the output turns on. |
| | |
| |Also the chip controls when the capacitor charges and discharges, so it keeps everything going in a |
| |loop. |
| | |
| |Show them a chip and explain how the pins correspond to different functions, but we don’t need to |
| |worry too much about them. |
| | |
| |The chip needs power just like our circuit needs its own power since there’s just more circuits inside|
| |the chip |
|Computer Applet |Have the students go to the applet which shows the circuit they will build: |
| |ž |
| |žChoose Circuits → 555 Timer Chip → Square Wave Generator |
| | |
|10 min |Get the applet up on your screen so you can show it to them. |
| | |
| |Ask the students to identify each component on the diagram. |
| |Point out how the power and ground act like the positive and negative terminals on our batteries |
| | |
| |Point out the graphs at the bottom showing the voltage on the capacitor (green graph on left) and the |
| |output voltage. You can see the capacitor charging and discharging as the output goes on and off. |
| | |
| |Slow down the animation so they can watch the current flow in to the capacitor and see the voltage |
| |rise. Then point out how when it gets to a certain point, the chip changes the output to low, then the|
| |capacitor discharges through the chip. Try to make sure they understand. Tell them we are going to |
| |build this circuit but with an LED on the output of the chip |
|Building the 555 Circuit |Everyone should already have the parts they need and a circuit diagram handout. Pull up the circuit |
| |diagram on the projector. |
| | |
| |Step the students through the wiring process one step at a time. Make sure almost everyone is caught |
| |up before continuing. First start by explaining how to use the rails or buses on the breadboards to |
|30 min |supply power. Plug the battery connection wires into the right red rail (the red wire) and the |
| |leftmost blue rail (the black wire). Remind students not to attach the battery yet. |
| | |
| |Next have the students carefully put in the 555 chip, making sure the little dot on the top is |
| |pointing up (having everyone do it this way not only assures consistency when we are explaining the |
| |circuit, it also puts the correct power buses on the right sides of the chip) |
| | |
| |Next have them wire the power and ground to the chip, using the red wire for + and black wire for -. |
| |Explain how we follow this convention to make things look simpler. Then make connections between the |
| |chips pins using the resistors and the blue wires. As you make each connection, cross off or check the|
| |corresponding wires on the diagram on the screen. |
| | |
| |Then put the capacitor (have everyone use the smaller one) into the circuit, making sure it’s put in |
| |the right way. Finally the resistor and LED should be put in, reminding the students how to use their|
| |breadboards and that the LED can only go one way. Also remind students of how this is almost exactly |
| |like the circuit they built earlier. |
| | |
| |Finally the students can connect the battery and test the circuit. Help any student’s whose aren’t |
| |working, making sure to check that the wires are pushed in enough, they are to the right places, the |
| |LED is not faulty or burned out. If the 555 timer feels hot to the touch, it probably needs to be |
| |replaced. |
|Exploring the 555 Circuit |When the students are done building their circuits, ask them how they could change how fast their |
| |light blinks. Make sure they understand that a bigger capacitor will take longer to charge and thus |
|10 mins |the light will remain off longer and on longer. |
| | |
| |Have them come up with a guess, then unplug the battery and change the capacitor. Where they right? |
| | |
| |Ask them if there is any other way to change how long the light is on. Hint at other ways to change |
| |the time, like giving it less current. If you have different sized resistors and want to have them try|
| |it you can. |
|Reflections |Reflections |
|15 min | |
|Extra Time |The students can explore other circuits on the applet site if there is extra time. Also, if there’s a |
| |lot of time, a brief introduction to digital electronics could be useful. |
|Bibliography |
|Part of this lesson, including the 555 circuit was originally designed by Professor Dr. Rhett Davis of NC State University |
................
................
In order to avoid copyright disputes, this page is only a partial summary.
To fulfill the demand for quickly locating and searching documents.
It is intelligent file search solution for home and business.
Related searches
- you are important to me
- how to write a lab report
- how to write a lab report example
- are employers required to provide pay stubs
- what is required to become a teacher
- when are you contagious with the flu
- how to format a lab report
- how to get a decent mortgage with bad credit
- you are entitled to your opinions but
- you are entitled to my opinion
- you are entitled to your opinion
- list the equipment required to measure the following and name the type of sampli