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555 Timer Circuit: An In-Depth Analysis

Directed Studies: Physics

William Tadekawa

on 16 May 2011

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Transcript of 555 Timer Circuit: An In-Depth Analysis

William Tadekawa
Directed Studies: Physics
Mr. Huntington
2010-2011 555 Timer Circuit: An In-Depth Analysis Background Information Hypothesis Objective Conclusion Data Integrated Circuit (IC)
Light Emitting Diode (LED)
LOW Time
Duty Cycle
Mark Space Ratio A fabricated device made up of various electronic components. Bulbs that are illuminated by movement of electrons in a semiconductor material. A device used to store electric charge. Component which controls the flow of electricity. A measure of the energy of electricity. Also known as the electrical potential difference.
Voltage (V) = Resistance (R) x Current (I) The rate of flow of an electric charge through a conductor.
Current (I) = Voltage (V) / Resistance (R) The objective of this project is to design and construct/demonstrate a safe astable RC timing circuit (visibly displayed by an LED), varying composition and capacitance to find the relationships between current, voltage, capacitance, resistance, and period in the circuit. If the capacitance, resistance, and voltage connected to a 555 IC timer circuit are increased, the period of the flashes (displayed by an LED) will also increase because the equation, period = (ln2)(R1 + 2R2)(C), suggests that increasing the resistance and/or capacitance will result in an increase in the period of the discharges. The voltage V2 will also affect the period because Pin 5 in the 555 IC allows the period to be altered independently of the RC network by directly applying voltage to this pin. 555 IC Ground: Negative power supply Trigger: Output to high state Output: Connects to various components, e.g. an LED Reset: Output to low state V+: Positive power supply Discharge: Timing aspect Control Voltage: Controls timing aspect independently using an alternate power supply Threshold: Timing aspect Experiment #1 Experiment #2 Experiment #3 Experiment #4 Timing precision +/- 0.5 sec. (human reaction)
Wire/alligator clip resistance
Breadboard resistance Uncertainties Variables Independent - C1
Dependent - Period
Controlled - R1, R2, V1 Graphs [Graphical Analysis] Circuit Uncertainties Graphs Variables [Graphical Analysis] Uncertainties Graphs Variables Uncertainties Graphs Variables Timing precision +/- 0.5 sec. (human reaction)
Wire/alligator clip resistance
Breadboard resistance
Battery voltage accuracy Independent - V2
Dependent - Period
Controlled - R1, R2, V1, C1 [Graphical Analysis] Timing precision +/- 0.5 sec. (human reaction)
Wire/alligator clip resistance
Breadboard resistance Independent - R1
Dependent - Period
Controlled - C1, R2, V1 Wire/alligator clip resistance
Breadboard resistance
Current Leakage
Multimeter Precision Independent - R1
Dependent - Current
Controlled - C1, R2, V1 [Graphical Analysis] Resistance vs. Period Voltage vs. Period Capacitance vs. Period Resistance vs. Current Number of cycles per second. Number of seconds per cycle. The time the capacitor is charging/the time the LED is off. The time the capacitor is discharging/the time the LED is on. The percent of a cycle that the capacitor is charging. HIGH Time:LOW Time Schematic Diagram
[Microsoft Word] Thank you! • Frequency = f = 1/[(ln2)(R1+2R2)C]
• Period = T = (ln2)(R1+2R2)C
• HIGH Time = (ln2)(R1+R2)C
• LOW Time = (ln2)(R2)C
• Duty Cycle = HIGH Time/Period
• Mark Space Ratio = (HIGH Time):(LOW Time) Equations Questions? Pictures:
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