A special circuit is required of all software-dominant projects

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Here is the archive for historic special circuit problems. 

Circuit #1

Design, assemble, and test, a clock (timer) circuit with the following characteristics. The design characteristics are below, with the (±) values the acceptable tolerances of the tested circuit (and consequently, drive the circuit component value tolerances).

• The clock should be 0-5 v (± 5 %).
• Your frequency should be selected from the table below (± 3%), with a pulse width (± 5 %).
• Your pulse width may be either 1, 10, or 100 micro secs, but the selected width you choose must be such that the duty cycle of the clock is < 50% high.
• Using a linear 555 timer component is acceptable.

Some typical frequencies that may be assigned include: 2 Hz, 600 Hz, 3700 Hz, 11000 Hz.

Your two specification tests can be defined for the specification limits of frequency and/or pulse width in the design. An example of one of the specification tests could be: Given your frequency chosen is 900 Hz, the (± 3%) allows the tolerance in the output to be 873-927 Hz. Find the values for the frequency setting resistor value (measured) for the minimum and maximum frequency (measured). Document the results.

Circuit #2

Design, assemble, and test, a small-signal low-frequency (< 100 kHz) amplifier circuit with the following specifications (tolerances):

• Frequency response: Lowpass or Highpass, to be assigned
• Rolloff: Single pole response is sufficient
• Gain in passband: To be assigned; (± 5%)
• Corner frequencies: To be assigned; (± 3%)
• Input impedance: 500 ohms at 1 kHz; (± 5%)

For the tolerance analysis portion of your senior project, you must characterize your circuit for two (2) of the above specifications. For each spec, you must choose a component that affects your circuit's ability to stay within the given tolerance. For example, you could pick a bias resistor and see how it affects the passband gain. What range of values are acceptable for that resistor? Document the results.

Circuit #3

Design a voltage regulator that meets the following specifications:

• Output voltage level within 3% of assigned value (TA will give you the voltage level)
• Must be able to deliver a maximum current of 2A
• Must be robust to reverse polarity of the input supply voltage

For the tolerance analysis portion of your senior project, you must characterize your circuit for two (2) of the above specifications. For each spec, you must choose a component that affects your circuit's ability to stay within the given tolerance. For example, you could pick a resistor and document what affect is has on the output voltage level. What range of values are acceptable for that resistor? Document the results.

Circuit #4

Design an audio oscillator that meets the following specifications:

• Four different frequencies (TA will give you the voltage level)
• THD less than 1% for frequencies above 1 kHz and less than 3% for those around 100 Hz
• Output voltage level should be individually adjustable for each frequency
• Sequencing rate control between 3 seconds and 30 seconds (TA will give the value)

For the tolerance analysis portion of your senior project, you must characterize your circuit for two (2) of the above specifications. For each spec, you must choose a component that affects your circuit's ability to stay within the given tolerance.

Circuit #5

Design and implement a simple ultrasonic transmitter/receiver meeting the following specifications:

• Power supply should be 9V, 12V or 15V (TA will assign the voltage level)
• The transmitter should generate a signal between 40-60 kHz. (TA will assign center frequency)
• The receiver stage should receive the center frequency generated by the transmitter and should trigger an electronic device (given by the TA)

For the tolerance analysis portion of your senior project, you must choose two of the above components that affect the performance of your circuit. Document your results.

Circuit #6

Design, assemble, and test an audio amplifier with the following characteristics:

• The amplifier must operate within the audio frequency range (exact values determined by TA)
• The output decibel in the passband must be within +/- 5% of a value to be determined by your TA
• The output impedance must be 4 or 8 ohms (assigned by TA)

As part of the tolerance analysis, you must select two components of your design and determine their effect on the output of the system. Analyze the appropriate ranges of values for given components and document the results.

Circuit #7

Design, build and test a current driven square wave generator with the following specifications:

• A minimum pulse height in the range of 3-5V, to be assigned by your TA
• A minimum pulse width in the range of 1-10s, to be assigned by your TA
• The output pulse frequency must be dependent upon the current input from a photodiode
  • Correlation between input current and output frequency is your choice
  • Must have accurate current measurement within ± 3%

As part of the tolerance analysis, you must select two components of your design and determine their effect on the output of the system. Analyze the appropriate ranges of values for given components and document the results.

Circuit #8

Design build and test a circuit to modify the speaker output signals from a computer.

You will be provided with the left and right speaker signals separately.

The circuit should have the following specifications:

• Create a subwoofer output that utilizes the lowest 100-300Hz, to be assigned by your TA
• Modifies the left and right speaker inputs separately in one of the following frequency windows -12dB to +12dB
• The unchanged frequency bands must remain within 3% or their original values. (spectral density)
• The output impedance must be 4-5 Ohms

As part of the tolerance analysis, choose two components of your design and determine their effect on the output of the system.

Circuit #9

Special circuit, Fall 2004

Design, build and test two notch filters, one passive and one active.

• Each filter should block f=60 Hz.
• Measure the -3 dB points and calculate the bandwidth of each filter.
• Calculate the quality factor, Q, of each filter.

As part of the analysis, choose two components of your design and determine their effect on the output of the system. Additionally, explain the performance differences between the passive and active filters, specifically explain how changes in the source and load effect each filter.

Circuit #10

Special circuit, Spring 2005

Design, assemble, and test a narrowband bandpass filter with the following tolerances:

• Center frequency: To be assigned in 1-10 MHz band (± 3%)
• 3-db bandwidth: Must be 0.01 percent of center frequency, ex. if fc = 5 MHz, the BW = 500 Hz.
• Filter should be constructed using an active topology using as few components as possible (BiQuad, Sallen-Key for example)
• Rolloff > -200 dB/decade
• We may also add a specific time response requirement as well

Simulate your design in PSpice, ADS, etc. As part of the tolerance analysis, choose two components of your design and discuss their effect on the output of the system.

Circuit #11

Special circuit, Fall 2005

Design, assemble, and test a linear DC voltage regulator with the following specs:

• 3% output voltage regulation (assigned 5V, 12V, or 15V dc)
• input voltage range of 1x to 2x assigned output voltage (i.e. for 10V output, input voltage is 10-20V)
• Must be capable of .5A output current
• <70dB noise rejection at 10kHz

For the tolerance analysis portion of your senior project, you must characterize your circuit for two (2) of the above specifications. For each spec, you must choose a component that affects your circuit's ability to stay within the given tolerance. For example, you could pick a resistor and document what affect is has on the output voltage level. What range of values are acceptable for that resistor? Document the results.

Circuit #12

Special circuit, Spring 2006

Design, build, and test a clock with current amplification. The specifications are as follows:

Clock

• 50/100 Hz clock
• 0-5 VPP (+/- 5%)
• 25/50% duty cycle
• +/- 5% tolerance

Current amplification stage

• Use the above clock to drive a 0.5 amp load (a resistor is sufficient)

You should demonstrate the clock tolerance specifications via an oscilloscope graph under load conditions. A digital multi-meter (DMM) should be used to verify that the nominal load current is 0.5A. Your TA will assign you the clock specifications (50 Hz clock with a 25% Duty Cycle, 100 Hz clock with a 50% Duty Cycle, etc.). It is OK if you over-design your current amplifier to drive more current than specified. Show calculations for all design aspects of the circuit. Be prepared to do a walk through of how your clock and current amplifier work.

Circuit #13

Special circuit, Fall 2006

A PDF is available here for your convenience.

Using off-the-shelf components (do not wind your own inductors) from the Electronics Shop or ECE Stores, design, construct, and test, two notch filters. One will be passive RLC and the other will be active RC, based on an operational amplifier. The filters must meet the following specifications:

• Center frequency assigned by TA (not to exceed 20 kHz), to within +/- 3%
• Minimum parts-count. (Hint: Don't do any more work than you have to.)
• Each design should be supported by an appropriate simulation using SPICE, MATLAB, or ADS, to obtain the transfer function.
• Provide a written summary of your design and analysis to be handed-in at the time of circuit check-out. (Maximum two pages, including simulations and schematics!)

Analysis

• Measure the actual center frequency of each filter.
• Measure the -3 dB points and calculate the bandwidth of each filter.
• Compute the loaded quality factor, Q, for each filter.
• Include a detailed description of your test configuration, showing all pertinent information.
• Test or model the effects of changes in source and load impedances. What can you conclude?
• In either the active or passive filter, study the effects of the tolerance of one component. This only needs to be done in simulation. Either worst-case or Monte Carlo analysis would be appropriate here.
• Although this does not need to be included in the written report, be prepared to discuss the advantages and disadvantages of the active and passive designs, as well as techniques for stablizing the response to varying input or output impedances during check-out.

Circuit #14

Special circuit, Spring 2007

A PDF is available here for your convenience.

Your task is to construct a circuit that provides a continuously-variable phase shift over at least 150° of the range 0°—90° while maintaining nearly constant amplitude. The circuit must operate with input and output impedances of approximately 50 Ω. The center frequency will be assigned by your TA in the range of 200 kHz to 2 MHz; but, the TA may elect to evaluate your circuit anywhere within the octave. The circuit must contain a maximum of two active devices, one (and only one) potentiometer, and any number of fixed resistors and capacitors you wish to employ. Do not use inductors, transformers, or any other components.

Evaluation

Provide a short (2-page maximum, including figures) summary of the circuit design. There is a classic oscilloscope technique for comparing the phase and frequency of two signals that will allow you to observe the performance of the circuit at a glance. Name the technique and include a modeled plot of the expected oscilloscope plots for phase shifts of 0°, 45°, and 90°. The plots will look something like the plot below; although, they will differ in important ways. The TA will have you test your circuit at several phase/frequency
points during check-out.

Hints

The limitation of two active device, one potentiometer, resistors, and capacitors, is intended to make the problem easier for you. The active device(s) can serve the role of a buffer(s), Q-multiplier(s), synthetic inductor(s), or gain stage(s). The potentiometer should (obviously) be used to control the phase. Commercial circuits exist to perform this function. Think of possible applications. A book on filter design may be a good place to start; however, there are several possible approaches to this problem.

Circuit #15

Special circuit, Fall 2007

Design, assemble, and test a linear DC voltage regulator with the following specs:

• 5% output voltage regulation (assigned 6V, 9V, or 13V dc)
• input voltage range of 15V to 30V
• Must be capable of .6A output current
• <60dB noise rejection at 10kHz

The project cannot consist of a simple commercially available voltage regulator. Make sure that all specifications are met.

Analysis

For the tolerance analysis portion of your senior project, you must characterize your circuit for two (2) of the above specifications. For each spec, you must choose a component that affects your circuit's ability to stay within the given tolerance. For example, you could pick a resistor and document what affect is has on the output voltage level. What range of values are acceptable for that resistor? Document the results.

Circuit #16

Special circuit, Spring 2008 Special circuit

Build a Class-A audio amplifier.

Specifications:

• Output power: (1,3,5) W output through an (4,8) Ω load
• Frequency response: ± 0.5 dB from 100-15 kHz
• Efficiency:efficiency greater than 30 % maximum (when the ouput is dc)
• Frequency response plot of speaker and the amplifier

Circuit #17

Special circuit, Fall 2008 Special circuit

Implement a range finder.

Design and implement a simple ultrasonic transmitter/receiver to implement a range finder meeting the following specifications:

• The transmitter should generate a signal between 40-60 kHz. (TA will assign center frequency)
• The receiver stage should receive the center frequency generated by the transmitter and should trigger an electronic device.
• The circuit should indicate when when an object (book) is placed 3 feet in front of it.
• The indicator could be a buzzer or an LED.





 
•  
•  
• * Hints will be forthcoming. *

Circuit #20

Special circuit, Spring 2010 Special circuit

Implement a Digital to Analog Converter.

Design and implement a Sigma-Delta or PWM type Digital to Analog Converter meeting the following specifications:

• Design and build a Digital to Analog Converter utilizing either a sigma-delta approach, or by generating a PWM in your own way.
• If PWM is used, you may not use a PWM driver. Instead, generate the PWM signal using discrete logic circuitry of your own.
• The digital input will be four bits, in a parallel connection.
• You will be given an output voltage range for the analog out.
• You will be given an "oversampling" rate to implement. Make sure you understand what this means, and are able to explain how this is achieved in your implementation. Be mindful of the time-scales you use in your design. Your circuit should have high enough bandwidth for a simple audio application.
• Demonstrate this working circuit, and explain it to me sometime before finals week. When it is working, email me and we can set up a time for your demonstration.

Circuit #21

Special circuit, Fall 2010 Special circuit

Design and build a Digital Ammeter

You must build a three-digit digital ammeter with the following specifications and limitations:

• Your TA will assign the range of currents to be sensed.
• Current to be sensed will flow through a resistor of your choice. This resistor must be able to carry the amount of current (1/4 watt resistor will probably not work), and should be as low resistance as possible, no more than 0.3 Ohms! The current you are sensing should not flow through any other portion of your circuit other than this resistor. Since the value of this resistance will be known, the current can be measured using the voltage drop across this resistor.
• You may use any analog to digital converter, but do not use a microcontroller. Signal conditioning must be done to ensure that the full range of the analog to digital converter is used. Protection must be in place to prevent the analog voltage input to the A/D converter from exceeding its limits.
• The digital value should be displayed on three 7-segment displays as three digits. The number displayed must be decimal (not hex), and should display the current in mA.
• You may use any digital logic chips to convert the digital signal from the A/D converter to the appropriate inputs to your displays, but do not use a microcontroller.
• You may use a lab power supply to power the circuit.
• Must be within 10% accuracy across the entire specified range of currents.

Circuit #22

Special circuit, Spring 2011 Special circuit

Given the circuit shown above, build a circuit protection circuit that will:
 

• Detect a maximum current (to be provided by your TA) flowing through the load circuit and open a switching device that will cut off current flow to the load circuit.
• Detect a maximum voltage (also to be provided by your TA), and also open the switch if a the maximum voltage is exceeded.
• When the switch is opened, it should not re-close until a reset signal is given to the control logic.

You may use A/D converters to convert the voltage and current signals to a digital signals, but not a micro-controller. The control logic should be electrically protected from the load circuit. You may use a separate power supply to power the control circuit. You are only allowed to use “discrete” chips such as op-amp, A/D converters, TTL logic and such.

The switch can be MOSFET or any other switching device of your choice that is available from the ECE parts shop. The switch should be closed while the current is within acceptable range and the voltage is under the maximum voltage; when the maximum current or maximum voltage is exceeded, the switch should open. You must have at least 10% accuracy in determining the current cutoff and maximum voltage.

Circuit #23

Special circuit, Fall 2011

Design, assemble, and test a voltage regulator that meets the following specifications:

• Maintains a steady state output voltage level with any ripple or DC offsets that is within ±5% of assigned value (TA will give you the desired input and output voltages).
• Capable of delivering an output current of 0.5 A.
• Robust to reverse polarity of the input supply voltage.

For the tolerance analysis of your special circuit, you must characterize your circuit for two (2) of the above specifications. For each spec, you must choose a component that affects your circuit's ability to stay within the given tolerance. For example, you could pick a resistor and document what affect is has on the output voltage level. What range of values is acceptable for that resistor? Document the results.

Circuit #24

Special circuit, Spring 2012

Design, build, and test a listening device that illuminates while generating an audible tone when activated by another audible tone in a specific frequency range. The specifications are as follows:

1. The circuit must be built on a solderable, perforated circuit board.
2. The circuit must be self contained, powered by your choice of standard (AA, AAA, C, D, 9V) batteries.
3. Use of micro-controllers or programmable logic is disallowed.
4. The circuit must detect tones from 750 - 1500 Hz with a sound pressure of 50 dB or greater.
5. The circuit must ignore tones below 375 Hz or above 3000 Hz at a sound pressure of 50dB or less.
6. A CMB-6544PF microphone is specified and provided.
7. An AST-03008MR-R speaker is specified and provided.
   • The speaker is to be driven with a square-wave.
   • The square wave may or may not cross zero volts, this choice is left to the designer.
   • It is expected that harmonics emitted from the speaker may dominate the fundamental at frequencies in the specified output range f1, due to speaker and drive circuit transfer characteristics.
   • This is considered normal operation.
8. When a tone satisfying specification 4 is detected, the following will occur in sequence:
   • The circuit will inhibit detection (i.e., stop listening).
   • A conveniently adjustable time t1 = (1, 3) seconds will pass.
   • The circuit will illuminate and simultaneously drive the speaker with a square-wave at frequency f1 to produce a tone for a fixed time t2 = 500 milliseconds, (375-625) milliseconds is acceptable. The fundamental frequency f1 of the tone will be specified by the TA in the range of C5 to C6 on the chromatic scale.
   • After another conveniently adjustable time t3 = (0.5, 3.5) seconds, the circuit will re-enable detection (i.e., resume listening). That is to say, the entire cycle completes after t1+t2+t3 seconds.
9. The circuit must have a reset button that will trigger the LED and tone generation.
10. Times t1 and t3 are both adjustable by the end user. Actual adjustable ranges may exceed those specified, however, reasonable dynamic range must be maintained within the specified ranges.

Circuit #25

Special circuit, Fall 2012
 

Design and build a Digital Ohmmeter

You must build a digital four-point ohmmeter with the following specifications:

• The circuit must be built on a solderable, perforated circuit board.
• Circuit that the student designed should have some sort of over-current and reverse-polarity protection
• Your TA will assign the range of resistances to be checked
• The Analog to Digital converter will be provided (ADC0801-05)
• The values should be displayed on a 8-bit binary display utilizing the full range with a 1k resistor registering as a zero.
• You may use any digital logic chips to convert the digital signal from the A/D converter to the appropriate inputs to your display, but a microcontroller is not allowed.
• Must be within 5% accuracy across the entire specified range of resistances

Circuit #26

Special circuit, Spring 2013

Design, build, and test a controllable tone-generating device that illuminates while generating an audible tone when activated by logic signal. The specifications are as follows:

1. The circuit must be built on a solderable, perforated circuit board.
2. The circuit must be powered by ±5V rails and ground.
3. Use of micro-controllers or programmable logic is disallowed.
4. The circuit must detect and trigger off of a logic high signal of 5V±0.2.
5. An AS02708CO-R speaker is specified and provided.
   • The speaker is to be driven with a square or triangle wave; this choice is left to the designer.
   • The driving wave may or may not cross zero volts; this choice is left to the designer.
   • The speaker must produce a tone that is clearly discernible from 10 feet away.
6. When a signal satisfying specification 4 is detected, the following will occur in sequence:
   • The circuit will inhibit detection of logic inputs.
   • The circuit will illuminate an LED and simultaneously drive the speaker with the generated wave at a frequency specified by the TA to produce a tone for an adjustable time t1 = (0.1-1.0) seconds.
   • The circuit must then send a logic high signal of 5V±0.2 for a fixed time of t2 = 100 milliseconds, 75-125 milliseconds is acceptable.
   • The circuit will then resume polling for logic inputs.
   • The entire time that the circuit is in operation t=t1+t2 it will not be listening for a logic input.
7. The circuit must have a trigger button that initiate the operational sequence detailed in 6.
8. The circuit must also contain over current and reverse bias protection of some kind.
9. The connectors that will be used to interface the logic signals and power to the circuit will be provided.
   • The input connector will consist of the following connections: +5V, -5V, GND, and an Input Signal.
   • The output connector must have the following: supply pins of +5V, -5V, GND that directly coupled to the supply pins of the input connector before any circuit protection takes place and an Output Signal.
10. Time t1 is adjustable by the end user. The actual adjustable range may exceed what is specified, however, reasonable dynamic range must be maintained within the specified range.

Circuit #27

Special circuit, Fall 2013

Design and build a Range-Finder

You will build a range-finder circuit with the following specifications:

• It will use a distance sensor (Sharp gp2y0a02yk provided).
• It must determine the relative distance between the position of an object and a variable reference position.
• The variable reference position must be user-selected with a potentiometer (provided).
• Both the position of the object and the variable reference position will be between 20cm - 140cm away from the sensor.
• The difference (in cm) must be displayed by 7-segment displays.
• The difference displayed should be within +/- 1cm of the actual measured distance as measured by a meter-stick.
• You may use a parallel output ADC (several types available from the ECE Service Shop).
• You may not use a microcontroller.

Circuit #28

Special circuit, Spring 2020 (simulation due to COVID-19)

Design a voltage converter with negative feedback control to achieve a stable output voltage (DC) with a slowly varying input voltage (DC). For this project, the load at the output is 50 Ohm, the input voltage is <ranges to be given, lower than the output>, and the target output voltage is 25V.

There are four requirements:

1. voltage ripple at the output should be no larger than 5% peak-to-peak
2. The average value output voltage should be within 1% of the target value
3. The circuit has protection from an inversed input voltage (circuit won’t be damaged by an inversed input)
4. The output voltage should be settled within 500 ms

Use LTspice as the simulation tool, if you are not familiar with LTspice, just google it, you should be able to find plenty of resources.  

You can use non-ideal switch and diode, and you can have ideal RLC, OpAmp, and other components. For clock generation, you can have only one ideal sawtooth waveform. Here is a tutorial to import the PSpice model if you can find the PSpice model provided by manufacturer:

https://www.analog.com/en/technical-articles/ltspice-simple-steps-to-import-third-party-models.html

To demo the simulation, we will use Zoom and you can share your screen on Zoom. I will ask you to set your input voltage to a specific value within the given range, and you need to run the transient simulation without manually setting any parameter in your circuit, the output voltage should be settled to the target output within 500 ms.

I may also ask you how to derive the choice for the value of the inductor and capacitor to test your understanding.

Hint:

1. Starting with Matlab Simulink is highly recommended.
2. Use PI control.
3. The time required for settling may take a longer time than what you expected, if you do not get your expected result, try longer simulation time.
4. The simulation will take a long time, so start earlier.