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,

orange) 1 9V Battery

3 Resistor, 1 K-Ω (brown, black,

red) 1 9V Battery Holder

1 10 uF electrolytic capacitor 1 555 Timer Chip 1 0.01 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.

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 1/10th 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.

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

http://www.dummies.com/how-to/content/electronics-projects-how-to-make-an-led-flasher-us.html

(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:

1 555 timer chip (RadioShack 276-1718)

2 10 k resistor (brown, black, orange)

1 0.01 uF ceramic disk capacitor

2 pushbuttons (RadioShack 275-1547)

10 Jumper wires (various lengths)

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.

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 F17.

4. 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.