Breadboard Electronics LED flasher

Transcription

1 Breadboard Electronics LED flasher Your Activity Make an LED flasher using a timer chip Material 1 Small solderless breadboard 2 5mm Red LEDs 1 Resistor, 10 K-Ω (brown, black, 1 9V Battery orange) 3 Resistor, 1 K-Ω (brown, black, red) 1 9V Battery Holder 1 10 uf electrolytic capacitor Timer Chip uf ceramic disk capacitor 8 Jumper Wires Circuit Worksheet LED Flasher Multimeter (Optional) Create 1. Insert the 555 timer chip in the center of the board 2. Insert the jumper wires using schematics in attached Circuit Worksheet LED Flasher. 3. Insert the resistors. 4. Insert the capacitors. 5. Insert the LEDs. 6. Connect the battery. 7. You are finished! Test your circuit. Do the LEDs flash when the battery is connected? 8. (Bonus) Add switch to the circuit, so LEDs only flash when the switch is pressed Science Topics Electrical Engineering, Electricity What s going on? Breadboards are often used for testing new designs since they do not involve soldering. Breadboarding is an essential skill for anyone who plans to design analog and/or digital circuits.

2 Breadboard Electronics LED Flasher Activity Lead Notes Introduction In this activity, students will build a circuit that alternatively flashes a pair of LEDs. The circuit uses a 555 Timer chip configured to flash the LEDs. The resistor and capacitor values are chosen so that each LED stays on for about 1/10 th of a second. Learning Objectives Build a simple circuit using a solderless breadboard Explain that engineers use solderless breadboard s to test circuit design because these circuits may be changed quickly. Identify a battery, resistors, Capacitors, LEDs. Vocabulary Battery: Source of electrical energy Resistor: Limits energy flow and converts electrical energy into heat Capacitor: is a device that stores energy by accumulating an internal imbalance of electric charge LED Light Emitting Diode: converts electrical energy into light Breadboard: A solderless board for building electric circuits Schematic: A diagram of a circuit used by electrical engineers Multimeter: Device for measuring electrical quantities such as voltage Materials See the activity description Preparing Materials Check each multimeter and 9 V battery by turning the knob of the multimeter to the 20 V DC setting and touching the probes to the battery terminals. The multimeter should read more than 8.7 V. If the multimeter reads less than 8.7 V, try a second meter. If that still reads less than 8.7 V, try a new battery. Notes about Materials Ask students to not play with the insulated wire; they might poke or cut themselves or another student. Activity Sheet Copy the activity sheet Circuit Worksheet LED Flasher and distribute one per student (or team). Conduct Experiment Guide students in conducting the experiment. Split students into groups of two. Pass out electronic components. Tell the students not to connect the battery to anything until they are told to do so! Walk around and help the students as they work through the activity. If the LEDs do not light up, change the polarity of the LED by switching the leads. Check to make sure the students circuits are built correctly.

3 If the battery leads are hard to get into the breadboards, try twisting the strands of the wires to form a firmer end of the wire. At the end of the activity, ask the students to put the components back in their original bags. Collect the components from the students. The batteries go back in the boxes to keep the contacts from touch something metal and short circuiting. Background Information (Bonus) Modify to add a set/reset switch You can modify the circuit so that the circuit is controlled by two pushbuttons that function as a set/reset switch. When you connect the power to this circuit, LED1 turns on and stays on. When you press the set pushbutton, the two LEDs start flashing alternately and continue to flash until you press the reset pushbutton. For this project, we need all the parts from the LED flasher activity, plus the following: timer chip (RadioShack ) 2 10 k resistor (brown, black, orange) uf ceramic disk capacitor 2 pushbuttons (RadioShack ) 10 Jumper wires (various lengths)

4 Breadboard Electronics Worksheet: LED Flasher 1. Insert the 555 Timer Chip a. Put Pin 1 in hole E5 and pin 8 in hole F5 2. Insert the Jumper Wires From To A5 Any hole in the ground bus C3 C6 C7 C10 D6 G7 (This wire crosses over the top of the 555) D8 G5 (This wire also crosses over the top of the 555) H3 H6 F9 Any hole in the ground bus J5 Any hole in the positive voltage bus 3. Insert the resistors Resistor From To 10K D3 G3 1K J3 Any hole in the positive bus 1K B10 B13 1K D10 F13 4. Insert the capacitors Capacitor From To 0.01 uf G8 G9 10 uf A3 Any nearby hole in the ground bus 5. Insert the LEDs LED From To LED1 J13 Any hole in the positive bus LED2 Any hole in the ground bus A13 6. Connect the battery: Put the 9V battery into the battery snap connector, and then connect the red lead to the positive voltage bus and the black lead to the ground bus. The LEDs should begin flashing immediately when the battery is connected.

5 Breadboard Electronics Worksheet: LED Flasher with a Set/Reset Switch 1. Build the LED Flasher circuit 2. Remove the jumper wire you inserted from hole J5 to the positive bus to stop the voltage supply of 555 from previous activity. 3. Insert another 555 chip in the center with pin 1 in hole E17 and pin 8 in F Insert the additional jumper wires From To A17 Any hole in the ground bus I5 I15 E15 F15 D15 D19 C18 C23 D20 D27 F21 Any hole in the ground bus E23 F23 E27 F27 J17 Any hole in the positive voltage bus 5. Insert the resistors Resistor From To 10K J23 Any hole in the positive bus 10K J27 Any hole in the positive bus 6. Insert the capacitors Capacitor From To 0.01 uf G20 G21 7. Insert the pushbuttons Pushbutton From To Set A23 Any hole in the ground bus Reset A27 Any hole in the ground bus 8. Connect the battery: Put the 9V battery into the battery snap connector, and then connect the red lead to the positive voltage bus and the black lead to the ground bus. LED1 should immediately light up. 9. Press the Set button to start the LEDs flashing. Let them flash for a little while and then press the reset button to make flashing stop.