Lab 2 - LED Flasher
ENGI12195 - Practical Circuits
Sheridan College Institute of Technology and Advanced Learning
Faculty of Applied Science and Technology
Lab 2 - LED Flasher
Student Name_________________________
Student Number_________________________
Parts List:
U1: LM555 Timer IC
R3 & R4: 220 Ω resistor
R2: 100 KΩ resistor
C1: 15 μF Electrolytic (polarized) capacitor
R1: 470 Ω resistor
LED: Light-emitting diodes (any color)
Introduction
Fig. 1 - Top view of the 555 IC
Fig. 2 - polarized capacitor
Procedure:
Follow the following steps to build the circuit on the breadboard:
1. Set the Power-Supply (CH1) to 6 V. Make sure the Green key is OFF.
2. Connect CH1 positive to the breadboard VCC rail (Red stripe) and the negative to the GND rail (Blue stripe).
3. Insert the IC 555 into the breadboard (middle of breadboard). Notice that the small circle in the top left
corner shows pin 1.
4. Use a jumper wire to connect the pin 1 to the GND rail (see Fig.1).
5. Use jumper wires to connect the pin 4 and pin 8 to the VCC rail (see Fig.1).
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Lab 2 - LED Flasher
ENGI12195 - Practical Circuits
VCC
VCC
6V
R1
4.7kΩ
8
VCC
4
7
6
R2
10kΩ
2
5
C1
15µF
U1
OUT 3
RST
DIS
R3
220Ω
THR
TRI
CON
GND
C2
10nF
6V
1
LM555CN
LED4
Fig. 1 - LED Circuit Schematic
6. Use a jumper wire to connect pin 2 of the IC to pin 6.
7. Connect one pin of the 10nF capacitor (C2) to the IC pin 5 and the other pin of the C2 to the GND rail.
8. Connect the positive lead of the 15µF capacitor (C1) to the IC pin 2 and the negative lead to the GND rail.
9. Connect the 4.7KΩ resistor (R1) between pin 7 of the IC and the VCC rail.
10. Connect the 10kΩ resistor (R2) between pins 2 and 7 of the IC.
11. Connect the 220Ω resistor (R3) to the IC pin 3. Connect the other pin of the resistor into a free strip of the
breadboard.
12. Connect the anode of the LED to the free end of R3 and the cathode of the LED to the GND rail.
13. Check your circuit against the schematic diagram. Go around the IC and check that each pin is connected to
what the schematic says it must be connected to.
14. If you are sure that your circuit is correct, turn ON the Green key of the power-supply. Your LED should
blink now.
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