North Park Secondary School

Computer Engineering 11 (ICE 3M0)

Experiment 16

Digital Lab 16

Digital Clock Circuit


Teacher's Name

Student's Name

Student No.

PURPOSE:

To investigate the operation of a digital timer circuit.

Materials

One SK-50 breadboarding socket
One 555 integrated circuit
One 100 OHM resistor
One 1 uf capcitor
One 1K resistor
One LED
Seven Wires
One 9V Battery
Several resistors valued at 1 Meg "OMEGA", 680 K "OMEGA", 470 K "OMEGA", 100 K "OMEGA", 47 K "OMEGA".


Curcuit


PROCEDURE:

  1. Assemble the circuit on the breadboard with R2 initially at 47 K ohms.
  2. Use a watch with a second hand to record the number of seconds required for each LED cycle.
  3. Replace R2 with a variety of other resistors(1 MEG, 680 K, 470 K, 100 K, etc.) and record the number of seconds for each LED cycle.

OBSERVATIONS

R 2
Time sec./LED cycle
47 K
100 K
470 K
680 K
1 Meg
Other


DISCUSSION

  1. Review in chart form the results of the eight cases for subtracting 2 binary digits and a borrow.
    R
    e
    s
    i
    s
    t
    a
    n
    c
    e
    47 K
    100 K

    470 K

    680 K

    1 MEG

    Other



                       
                       
                       
                       
                  
        Time (seconds)

  2. Describe the type of curve obtained through the points.
  3. What common applications for this circuit can you think of?
  4. What change in the results would occur if a different value is used for the capacitor?

CONCLUSION

Summarize how the number of LED cycles per second varies with the resistance in this 555 timer circuit.


Page Lasted Updated 2:42 PM 09/22/2003

 

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