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    EE 2201 Touch Switch Project Manual

    Uploaded by

    Krishna
    This document describes a semester project to design and build a touch switch circuit using a 555 timer chip. The circuit will have two stages - the first uses a 555 timer and LED to generate an output pulse when touched, and the second adds a transistor and relay to control a load. Students will complete the project through simulation, adding an output design, and physical construction. They will analyze component specifications, simulate the circuit in stages, and propose a creative output application for their circuit, like a toy or doorbell. The goals are to learn 555 timer and relay fundamentals, circuit simulation, and real-world circuit applications.

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    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd

    EE 2201 Touch Switch Project Manual

    Uploaded by

    Krishna
    31 views5 pages
    This document describes a semester project to design and build a touch switch circuit using a 555 timer chip. The circuit will have two stages - the first uses a 555 timer and LED to generate an output pulse when touched, and the second adds a transistor and relay to control a load. Students will complete the project through simulation, adding an output design, and physical construction. They will analyze component specifications, simulate the circuit in stages, and propose a creative output application for their circuit, like a toy or doorbell. The goals are to learn 555 timer and relay fundamentals, circuit simulation, and real-world circuit applications.

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    EE_2201_Touch_Switch_Project_Manual

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    This document describes a semester project to design and build a touch switch circuit using a 555 timer chip. The circuit will have two stages - the first uses a 555 timer and LED to generate an output pulse when touched, and the second adds a transistor and relay to control a load. Students will complete the project through simulation, adding an output design, and physical construction. They will analyze component specifications, simulate the circuit in stages, and propose a creative output application for their circuit, like a toy or doorbell. The goals are to learn 555 timer and relay fundamentals, circuit simulation, and real-world circuit applications.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    31 views5 pages

    EE 2201 Touch Switch Project Manual

    Uploaded by

    Krishna
    This document describes a semester project to design and build a touch switch circuit using a 555 timer chip. The circuit will have two stages - the first uses a 555 timer and LED to generate an output pulse when touched, and the second adds a transistor and relay to control a load. Students will complete the project through simulation, adding an output design, and physical construction. They will analyze component specifications, simulate the circuit in stages, and propose a creative output application for their circuit, like a toy or doorbell. The goals are to learn 555 timer and relay fundamentals, circuit simulation, and real-world circuit applications.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 5

    D. Chattopadhyay Rev.

    FS 2016 EE 2201 Semester Project


    Touch Switch

    Preface:
    • All work to be done in groups.
    • 1 Tech memo for the entire project to be turned in as a group.
    (Tech Memo should include answers of: Preliminary Questions, Part 1 to Part 5 &
    Appendices).

    Description:
    The project circuit is a touch switch that generates an output pulse, which is
    indicated by an LED, and toggles a single pull, double throw (SPDT) relay. This circuit
    is useful for making touch operated products, such as doorbells, toys, buzzers, etc. For
    the circuit in this project, the 555 timer will be operating in the monostable mode, which
    generates a fixed output pulse based on the resistor and capacitor values on the
    discharge and threshold pins of the timer. A transistor is used to drive the relay and
    control the load, which is user defined and must be designed by each group.
    There are 3 parts to this project: simulation, output design and simulation, and
    circuit construction with demonstration.

    Objectives:
    • Learn and apply the fundamentals of a 555 timer.
    • Learn and apply the fundamentals of a relay.
    • Investigate the application of components in a circuit.
    • Learn how to simulate a circuit in Multisim 8.
    • Learn how to interact with a circuit simulation in real-time and observe the
    output.

    Equipment:
    This project encourages the use of simulation to develop working knowledge of
    the given project circuit before constructing and testing it.

    For the simulation portion:


    • Multisim 8

    For the construction portion:


    • 555 timer (8 pin IC)
    • 10MΩ resistor (R2)
    • 2 - 1kΩ resistors (R3,R4)
    • 100Ω resistor (R5)
    • 1k to 10MΩ resistor (R1)
    • 0.1 to 100uF capacitor (C1)
    • 2 - 1N4002 diodes (D1, D2)
    • 2N3904 BJT (Q1)
    • 6-9V Relay (use EDR201A05 Relay for simulation)
    • Red LED (D3)
    • SPST switch

    1
    • Breadboard
    • Power supply
    • DMM
    • Oscilloscope
    • Output components of your choice

    Touch Switch
    The touch switch circuit is given in Figure 1 and is split into 2 stages. Stage one of the
    circuit produces the output pulse using the 555 timer to turn on the LED (D3). Once the
    desired output pulse width is defined, then stage two is added to complete the circuit.
    The input voltage for this circuit can vary widely. Enough voltage should be applied to
    drive the 555 timer and relay, however, too much voltage could destroy the 555 timer or
    the relay coil. The output components will also need to be considered when choosing
    the input voltage. One should consider this circuit as a marketable product for a toy,
    game, gag gift, holiday decoration, etc. when designing the output portion of the circuit.
    Important design questions should be answered:

    Preliminary questions:
    I. What type of product am I designing?
    II. Would I be interested in purchasing it? If not, how can it be
    improved?
    III. Will this product be battery powered or use an AC adapter?
    IV. What age group is this product for?

    Figure 1: Touch switch circuit

    2
    Part 1 Questions (related to Data Sheet):
    1. Find and download the datasheet for a National Semiconductor LM555 Timer:
    (1A) Make a table listing the given values for the following: supply voltage,
    supply current, trigger voltage, and trigger current.
    Find and download a datasheet for the 6-9 V relay provided in the lab:
    (1B) Make a table listing the given values for the following: contact resistance,
    nominal voltage, max voltage, min voltage, max current, min current.
    (Put these tables in Appendix 1)

    2. Determine an adequate input voltage for the circuit based on the values
    provided in the datasheets. Enough voltage should be applied to drive the 555
    timer and relay, however, too much voltage could destroy the 555 timer or the
    relay coil.
    (2A). What is your chosen input voltage?

    3. Look in the datasheet for the application information section and read about
    monostable operation. Study the time delay chart, taking note of the
    resistance and capacitance values.
    (3A). What are all the combinations of C and R values that provide an
    output delay of 1 second (you can put 3 combinations)?
    -----------------------------------------------------------------------------------------------------
    Part 2 & 3 of the project involves circuit simulation and answering questions
    about the components within the circuit. Simulation begins with the first stage of the
    given touch switch circuit followed by an analysis. Part 3 involves simulation and
    analysis of the second stage of the circuit. Answer all questions listed below as a
    discussion in tech memo format. Create all specified appendices in tech memo format.

    Part 2 Questions (related to Stage 1 Simulation):


    4. Simulate Stage 1
    Build stage 1 of the Project circuit (Figure 1) and simulate it for 10 seconds.
    Use the input voltage stated in Q(2A). To simulate the touch input to pin 2, use
    a monetary switch or push-button.
    Q(4A). Observe how long the LED is on for chosen values of R1 and C1.
    Q(4B). Compare the output pulse to the values given in the 555 timer
    datasheet. [Note: Stage 2 components that should not appear in stage one
    simulations are: D1, D2, R4, R5, Q1, Relay, Output components.]
    Save the schematic. Use the oscilloscope function to generate waveforms for
    the input or pin 2 and output of pin 3. Put cursors to see the duration of
    pulse i.e the time duration for which the D3 LED was on. Save the waveforms.
    Make sure that each waveform is distinguishable when printed in black and
    white. Make separate graphs if you have to or use the excel export function to
    make dashed/dotted lines. (Put these images in Appendix 2)
    Q(4C). What is happening internal to the timer when the touch switch is
    activated?
    Q(4D) Why is there a 10MΩ resistor on pin 2 of the timer?

    3
    Q(4E) What values of R1 and C1 were chosen? What is the output pulse
    in seconds?
    Q(4F). Was the output pulse time as expected or as specified from the
    datasheet?

    Part 3 Questions (related to Stage 2 Simulation):


    5. Simulate Stage 2
    Add stage 2 to the previous circuit simulation and simulate it for 10 seconds. Use
    the input voltage stated in Q(2A). Use the example output after the relay from the
    project circuit given in Figure 1. To simulate the touch input to pin 2, use a
    monetary switch or push-button. Use a EDR201A05 Relay in your circuit, which
    can be found in the relay category of component group basic. This is a SPST
    relay with a NO contact, and not a SPDT relay like we have in the lab, but when
    the circuit is built only the NO will be required. **When simulating the full
    circuit, only tap the space bar (it simulates the function of the switch) once
    or an error will occur**.
    Q(5A). Observe how long the LED is on for chosen values of R1 and C1.
    Q(5B). Compare the output pulse to the values given in the 555 timer
    datasheet.
    Save the schematic. Use the oscilloscope function to generate waveforms for the
    input pin 2, output of pin 3, and the collector side of the BJT. Put cursors to
    see the duration of pulse i.e. the time duration for which the D4 LED was on. Save
    the waveforms. Make sure that each waveform is distinguishable when printed in
    black and white. Make separate graphs if you have to or use the excel export
    function to make dashed/dotted lines. (Put these images in Appendix 3)
    Q(5C). What color LED was used for the example output of the relay?
    What is the voltage drop across the LED?
    Q(5D). What are the purpose of diodes D1 and D2?
    Q(5E). Why is a transistor used to control the relay coil?
    Q(5F). With the added components and relay, was the output pulse
    time as expected or as specified from the datasheet?

    Part 4 Questions (Creative output):


    6. Assume that instead of the ‘example output’ which is just an LED (for the
    sake of simplicity) , you plan to put a creative output (which has some
    applications in the real world). **The questions followed in this section only
    demands theoretical aspects and your thoughtful imagination. You do not
    have implement these in simulation and hardware labs. **
    This part of the project involves designing the creative portion of the circuit. As
    a group, think of an output to the circuit (i.e. what is the circuit going to do?).
    As mentioned before, this circuit is useful for making touch operated products,
    such as doorbells, toys, buzzers, etc. The output components will need to be
    considered when choosing the input voltage. Consider this circuit as a
    marketable product for a toy, game, gag gift, holiday decoration, doorbell.

    4
    Q(6A). Explain the design and application for the output portion of the
    touch switch circuit that you’ve thought of.
    Q(6B). Does the new output design change the input voltage? Explain.
    Q(6C). What could be the new estimated input voltage when you add
    your own design output to the circuit??

    Part 5 Questions (related to Hardware


    implementation of the project):
    This part of the project involves constructing the circuit and demonstrating that
    it works as demonstrated by the simulation. Build each stage of the circuit in
    Figure 1 and then add the designed output portion. Answer all questions listed
    below as a discussion in tech memo format. Create all specified appendices in
    tech memo format.

    7. Construct stage 1 of Figure 1. Take oscilloscope measurements on this


    circuit just as you did in the simulation. Save a waveform that captures the
    input trigger and one that captures the output pulse. (Put these images in
    Appendix 4)
    Q(7A). What is the input voltage for the
    circuit?
    Q(7B). What are the values of R1 and
    C1?
    Q(7C). How does the experimental circuit
    output compare to the simulated circuit output?
    Q(7D). What is the percent difference
    between the output pulse length (in seconds)
    of the simulation and experiment?

    8. Add stage 2 of Figure 1 to the circuit of step 1, including the example


    output. **Try to use the same LED as specified in Q(5C) of Part 3** Take
    oscilloscope measurements on this circuit just as you did in the simulation.
    Save a waveform that captures the input trigger, one that captures the
    output pulse and one that captures the collector side of the BJT. (Put
    these images in Appendix 4)
    Q(8A). How does the experimental circuit output compare to the
    simulated circuit output?
    Q(8B). What is the percent difference between the output pulse length (in
    seconds)?
    of the simulation and experiment.
    Q(8C). Does the circuit operate as expected? Explain.

    9. Evaluate the lab project.


    Q(9A). Did you learn the objectives of this project?
    Q(9B). Was the project helpful for your education of electronic devices?
    Q(9C). What would you change about the project? Provide any general
    comments or suggestions.

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