+5 V R 1ΚΩ w R 470 ká 13 Output OUTPUT 6 Timer IC (555) LED DH 1500 Figure 2: Free-running clock circuit (astable multivibrator) Procedure Part B 1. Insert a 555 IC into the solderless breadboard so that the pins straddle the Dual Inline Package (DIP) channel that runs down the centre of the board. Take care not to bend the pins of the IC when inserting them into the breadboard. The pinout for the 555 IC is illustrated in Figure 1. 2. Construct the circuit illustrated in Figure 2. Use short jumper wires to extend connections away from the 555 IC. This will make it easier to exchange components, as needed, throughout the lab. (See Lab 2 Support Document: Image 1) 3. When building the circuit, make use of the continuous power distribution strips (red and blue strips top and bottom of breadboard) to create the +5V and GND points. 4. Use jumper wires to connect the circuit to the 5V pin and the GND pin found on the Arduino Uno Board. (See Lab 2 Support Document: Image 2) 5. Connect the Arduino USB cable to an open slot on the Station PC. 6. Connect the cable to the Arduino Uno and observe the output LED. It should be flashing at a low frequency 7. Connect the BNC end of a 1x probe to channel 1 of the oscilloscope. Connect the probe ends across the output. 8. Turn on the oscilloscope. Set the vertical to 2V/div and the horizontal to 200ms/div. 9. Use the measure tool on the oscilloscope to measure the frequency of the waveform and enter this value under Graph 1B. 10. Carefully sketch one complete cycle of the waveform. Remember to include the V/div and T/div on your sketch.
11. Disconnect the cable to the Arduino Uno. Graph 1A Graph 18 V/Div: V/Div: T/Div: Measured Frequency: T/Div: Measured Frequency: 12. Replace the 470k, resistor with a 100k2 resistor. Connect the cable to the Arduino Uno. Observe the LED. Use the measure tool on the oscilloscope to measure the frequency of the waveform and enter this value under Graph 2B. 13. Carefully sketch two complete cycles of the waveform. Remember to include the V/div and T/div on your sketch. 14. Disconnect the cable from the Arduino Uno. Graph 2A Graph 2B V/Div: V/Div: T/Div: T/DIV: Measured Frequency: Measured Frequency: 15. Replace the 1uF capacitor with a 4.7uF capacitor. Connect the cable to the Arduino Uno. Observe the LED. Use the measure tool on the oscilloscope to measure the frequency of the waveform and enter this value under Graph 3B. 16. Carefully sketch one complete cycle of the waveform. Remember to include the V/div and T/div on your sketch. 17. Disconnect the cable from the Arduino Uno and disable the circuit before proceeding. Graph 3A Graph 38 V/Div: V/Div: T/Div: Measured Frequency: T/Div: Measured Frequency:
Part C 1. Connect the power cable to the ELNC1224 Logic Board. Verify the Power ON/OFF switch is in the OFF position. Plug the board into an available power outlet. 2. Locate the 555 IC on the ELNC1224 Logic Board. 3. Insert the LED into the provided breadboard. Connect 1 end of a 1500 resistor to the Cathode of the LED and the other end of the resistor to the GND header located below the breadboard. 4. Connect a jumper wire from the Clock Out Header to the Anode of the LED. 5. Connect the positive scope probe lead to the Anode of the LED and the GND clip to the GND side of the resistor. (See Lab 2 Support Document: Image 3) 6. Switch the ELNC1224 Logic Board ON. 7. Turn the variable clock potentiometer for the 555 IC (located below the 555 IC). Observe the waveform on the oscilloscope as you adjust the potentiometer. 8. Turn the potentiometer fully counterclockwise. Measure and record the frequency. Measured Frequency: 9. Turn the potentiometer fully clockwise. Measure and record the frequency. Measured Frequency:
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