North Park Secondary School
Computer Engineering 11 (ICE 3M0)
Digital Lab 16
Digital Clock Circuit
To investigate the operation of a digital timer circuit.
|One SK-50 breadboarding socket
||One 555 integrated circuit
||One 100 OHM resistor
||One 1 uf capcitor
||One 1K resistor
||One 9V Battery
||Several resistors valued at 1 Meg "OMEGA", 680 K "OMEGA", 470 K "OMEGA", 100 K "OMEGA", 47 K "OMEGA".
- Assemble the circuit on the breadboard with R2 initially at 47 K ohms.
- Use a watch with a second hand to record the number of seconds required for each LED cycle.
- 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.
- Review in chart form the results of the eight cases for subtracting 2 binary digits and a borrow.
- Describe the type of curve obtained through the points.
- What common applications for this circuit can you think of?
- What change in the results would occur if a different value is used for the capacitor?
Summarize how the number of LED cycles per second varies with the resistance in this 555 timer circuit.
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