This is one of three files listing student projects: PIC projects | Student Projects for Leeds University | Student Project Suggestions
From 1998 to 2001 I helped to set and supervise final-year undergraduate projects in the School of Electronic Engineering at Leeds University. This is an extended list of project suggestions. Many of these projects are based on design work / consultancy / research I am doing. If you want to know more, please contact me. Eventually I might put some notes on this web site. (31/03/03, 18/2/01). New projects added 31/03/03 CONTENTS -------- Go to Projects 1-13 14. COFFEE THERMOMETER 15. INDUCTION ESCAPEMENT FOR PENDULUM CLOCK 16. INVESTIGATION OF STABILITY IN LOGIC CIRCUITS 1. COFFEE THERMOMETER --------------------- If you make a cup of instant coffee with boiling water it is too hot to drink, so you put it down somewhere and forget about it - and it becomes too cold to drink. What would be useful is a thermometer that sounds an alarm when the coffee becomes drinkable, and sounds a second alarm when the coffee starts to get too cool to be drinkable. To be easy to build and use, your hardware design should have minimal controls - can you design a circuit that does not need any switches (including an on-off switch)? How will you allow the user to calibrate the thermometer to his desired settings? (Hint: you might need a pushbutton switch to help with calibration). Although this project includes elements of hardware and software, the focus is on the detailed investigation of a "finite state machine". You will need to draw flow diagrams showing the transitions between the various states of the device, e.g. "waiting for coffee to cool", and allow for all possible sequences of states. Perhaps you could have different alarm signals to show the different conditions? A "coffee now ready to drink" alarm could be intermittent, getting ever more strident until the lost cup of coffee was located by its owner. How would you reset this condition without using a switch? How would a partially-drunk cup of cofee know that it had, once again, been put down somewhere and lost? 15. INDUCTION ESCAPEMENT FOR PENDULUM CLOCK ------------------------------------------- A pendulum clock contains a pendulum that swings with a regular beat, and a set of weights that provide the motive power to turn the clock's hands. The "escapement" is a device that allows the pendulum to regulate the motive power supplied by the weights. What is the other function of the escapement, and why does friction not stop the pendulum swinging after a few minutes? Many different designs of escapement were created during the period of development of mechanical clocks and watches; and, when electricity became available at the start of the 20th century, various electric escapements were designed. One of these used switches operated by the pendulum's movement to actuate electro-mechanical solenoids. The switches also provided the impulses to keep the pendulum swinging. The purpose of this project is to design an electrically-based escapement that does not require any electromechanical switches. The regulation is still by pendulum, but you will need to devise a "non-contact" method of detecting the pendulum's motion and of generating a "boost" signal to keep the pendulum swinging. This signal could be used to drive the movement in a standard electric clock mechanism. The pendulum's motion can be detected using an induction coil. Can you devise a method (based on a understanding of Faraday's law of Induction, and Lenz's law) that uses only a single coil to perform all the functions. (Hint: you will need to design some 'electronics' but this is simpler than it might seem to begin with). 16. INVESTIGATION OF STABILITY IN LOGIC CIRCUITS ------------------------------------------------ In digital hardware, the problem caused by gating asynchronous logic signals is almost completely ignored in the literature, with the result that engineers continue to disregard it, and to design systems that can fail, periodically. (Computer crashes are not all caused by software!). The aim of this project is to build a demonstrator circuit that is deliberately "bad" and to measure how often it fails, and to see if this agrees with a statistical analysis. Consider an external digital signal that is clocked into a bistable. This could be a microprocessor monitoring a push-button. What happens if the signal changes state at the same time as the bistable is clocked? Given that the system is "digital" you might expect that this problem would always resolve itself. Why doesnt it? Back in 1966, two authors wrote an analogy to explain this problem, the essence of which is this: An old lady sits in her house waiting for the postman and milkman to call. One always rings the front door bell, the other rings the back door bell. She has a rule that i) she doesnt answer a bell that hasnt been rung, and ii) she answers the first bell she hears. This works fine, provided that the two men do not call at the same time. However, she has foreseen this difficulty, so she has a third rule that if they both call at the same time she will answer the front door. She is confident that she has allowed for all eventualities but, one day, the milkman and postman arrive at the same time, and press the bells within a few milliseconds of each other. The old lady is fraught with indecision because this is on the threshold of her ability to distinguish the events. She cannot decide whether one bell rang first or whether they both rang at the same time. There she sits, indefinitely, trying to work out which rule to follow - her "system" has "crashed". You may think that she could resolve the situation, when she is in doubt, by just making an arbitrary choice, but this does not solve the essential difficulty which is that she now has to decide when she is in doubt! Can you explain the above problem in terms of digital electronics? What is the common name for the problem? How is is usually cured (when it is cured at all, that is)? We can analyse the problem statistically, beginning with random pulses entering a bistable that is clocked at a certain frequency, and calculating a) the probability that the bistable will enter an unstable state and b) how long it will remain in that state. Given the parameters that generate the statistics, can you choose suitable values to allow you to design a deliberately "bad" circuit that will fail at a conveniently measurable rate? Can you then demonstrate that the industry-standard "cure" for this problem really is a cure - e.g. by showing that it reduces your "bad" failure rate of one occurrence per minute (say) to less than one failure per day? Previous Projects: File: A dozen projects.doc last saved: 02/09/1998 09:07 CONTENTS -------- 1. PROTON MAGNETOMETER 2. TUNEABLE INDUCTION LOOP TRANSMITTER 3. SOLAR POWERED BATTERY CHARGER 4. MEMORY EFFECT IN RECHARGEABLE BATTERIES 5. PHOTOGRAPHIC FLASHMETER FOR CAVERS 6. INVESTIGATION OF THE PROXIMITY EFFECT 7. TELEPHONES - ART INSTALLATION 8. SUB-BASS WOOFER 9. MICROPROCESSOR-CONTROLLED CAPLAMP 10. UNDERWATER FLASHGUN SLAVE UNIT 11. SPEECH COMPRESSION 12. LASER RANGEFINDER 13. ELECTRIC KETTLE SWITCH 1. PROTON MAGNETOMETER ---------------------- In the earth's magnetic field, protons precess at around 2kHz. Having 'kicked' a bottle of protons (e.g. water) with a strong magnetic field they will precess about the earth's field emitting a signal that can be detected with a search coil and amplifier. Investigation: learn about nuclear magnetic resonance and proton spin; derive a formula for the frequency and magnitude of the signal you can expect. Build a receiver to detect this, and show how this could be used to make a magnetometer. Further work: what happens if - using feedback - you energise the protons with magnetic energy at the frequency of precession? Can you derive a tuned-circuit model for your bottle of water? 2. TUNEABLE INDUCTION LOOP TRANSMITTER -------------------------------------- Tuned induction loops are used for sub-surface communications. They tend to have a high Q and so are difficult to tune (e.g. proximity to the rock, changes in shape of the antenna and heating effects in the tuning capacitor all cause the resonant frequency to drift). The exact frequency of operation is not important it is more important to keep the loop in tune. Investigation: Design a variable frequency power amplifier for an induction loop that can be microprocessor controlled. This could use a DDS chip (e.g. ML2039), a class-C MOSFET amplifier with current feedback, and a PIC microcontroller (see CREGJ 30 for typical circuit). Further work: Devise a means of detecting whether the loop is in tune and deriving a 'tune up / tune down' signal to feed to the microcontroller. 3. SOLAR POWERED BATTERY CHARGER -------------------------------- A solar powered charger can be as simple as a solar panel connected to the battery - no other components are needed. However, as in all power-transfer problems, 'matching' is a concern. Solar panels have an ideal 'operating point' at which they will deliver the most power. Investigation: modelling a solar panel as a chain of photo-diodes, explain why connecting a so-called '12V panel' to a pair of 1.2V Ni/Cd cells will not normally result in damage. If the current is excessive, how can it easily be limited? Design a switching regulator (e.g. use a proprietary IC) to make such a charger more efficient. Further work: Devise a means of operating the panel at its optimum power-transfer point. 4. MEMORY EFFECT IN RECHARGEABLE BATTERIES ------------------------------------------ Rechargeable Ni/Cd batteries are often said to exhibit a 'memory effect' whereby repeated shallow discharge/charge cycles result in a reduction in battery capacity. On the other hand, repeated full cycles can reduce the lifetime. Heavy-duty sintered-plate cells (e.g. 4Ah D size, 7AH F size) are sometimes alleged - by users - not to suffer from the memory effect. Investigation: Find out the precise method used by manufacturers to determine battery capacity (it involves a specified charge regime and, importantly, a 'standing time'). Build a computer controlled charger/discharger that will allow you to collect data whilst you cycle a number of cells over a period of months. Further work: Program your cycler so you can gather data to allow you to evaluate the memory effect. Note: you may not have a long enough time to gather statistically viable data; so limit the investigation to C/5 rates. 5. PHOTOGRAPHIC FLASHMETER FOR CAVERS ------------------------------------- A flashmeter is a device that is used to estimate camera exposure when using a flashgun. In principle it is very simple, as it simply integrates the light input to provide a reading, but there are some interesting design issues; and for caving use, it will need to be rugged, waterproof, have few or no controls to operate, and must be readable in the dark. Investigation: Devise a method of integrating light flux over a period of 1/30th second and of calculating the logarithm of the mean light flux in order to obtain 'exposure'. Will you need to trigger the start of integration, or can your circuit operate continuously, storing a peak value? (Hint: a 'rolling integrator' is simpler than you might imagine, and does not need a microprocessor!). Further work: Can you adapt your unit so that it can accumulate successive flashes? (Cave photographers often let several flashguns off, over a period of seconds). How will you address all the issues of a cave-proof unit? Find out how light flux, film speed and 'exposure' are related. What is the difference between incident and reflected light exposure meters. 6. INVESTIGATION OF THE PROXIMITY EFFECT ---------------------------------------- The 'skin effect' is the observation that alternating electric current tends to flow in a 'skin' on the surface of a conductor, rather than penetrate it. In electromagnetic terms this can be explained using the diffusion equation. In broader terminology, the magnetic field produced by the current itself acts to 'push' the current to the edges of the conductor. The proximity effect is similar, but the magnetic field is from an external source, such as would be the case in a loop of wire or a solenoid. Investigation: Construct an induction loop, and a variable frequency power amplifier (see project 2) to drive it. Make measurements at different frequencies to establish how the combination of skin and proximity effects manifests itself. Why is this bad? Do your measurements agree with the simple theory for skin effect? (If not then the difference is probably the proximity effect). How can you isolate the skin and proximity effects to make more accurate deductions? Further work: Using Butterworth's 1923 paper (see CREGJ 19) as a guide, investigate different loop structures (wire diameter, wire spacing, winding cross-section) to see how you can minimise the proximity effect. 7. TELEPHONES - ART INSTALLATION -------------------------------- (removed from public list - please ask) 8. SUB-BASS WOOFER ------------------ Loudspeakers cannot reproduce sounds with a wavelength greater than the cone diameter (or something like that anyway). To get around this problem they are placed on baffles or in a sealed cabinet that acts like an 'infinite baffle'. However, this leads to a further problem, which is that the relatively 'stiff' mass of air in the cabinet restricts cone movement and attenuates bass frequencies. Filtering the signal to boost the bass can cure this. Investigation: You are supplied with a mathematical model of a sealed-cabinet speaker (as a Laplace transfer function). From this, deduce the form of the filter you must design. Derive a calibration method for the filter. Build a small sealed-cabinet speaker, using a 50mm Mylar cone speaker and a die-cast box. Check that it is waterproof! Further work: How efficient is the above system? Apart from an electronic filter, and without changing the size of the speaker or cabinet, how else could you increase the bass response (and efficiency) of such a system? 9. MICROPROCESSOR-CONTROLLED CAPLAMP ------------------------------------ High-current cap-lamps are used for caving, cycling, other outdoor activities, and commercially, as miners' lamps. Because battery voltage varies with time, the lamps must either be over-driven or under-driven at some point, and this leads to reduced lifetime or reduced efficiency. In addition, the filaments are subject to thermal shock when the lamp turns on, and this reduces the lamp life. Further problems are caused by switch reliability, and by accidental discharge if a lamp is left on. Investigation: design a simple PWM chopper that can regulate lamp current. The chopper should be controlled by a PIC microcontroller (or equivalent) to allow you to build in functions such as 'slow start' and 'auto turn off'. An outline of the project is given in CREGJ 33 (out soon!) Further work: design, in software, an 'intelligent' switch that can use a simple ruggedised momentary push- to-make switch to switch the lamp on and off and to perform other control functions, such a switching on a low current 'pilot beam'. 10. UNDERWATER FLASHGUN SLAVE UNIT ------------------------------------ Underwater photographers frequently need to trigger a flashgun remotely. In air, this is normally done with an infrared pulse, but infrared is attenuated by water. Visible light cannot be used as this would spoil the picture. Investigation: Design a trigger system to transmit a signal to a flashgun underwater, without using wires. The input to the transmitter will be the flashgun contacts on a camera. The receiver will plug directly into the flashgun. The transmission could be ultrasonic or radio, but bear in mind that waterproof (and pressure-proof) ultrasonic transducers are expensive, and that normal radio will not work underwater - you are limited to very low frequencies - try a 1kHz signal on a ferrite rod, using induction principles. 11. SPEECH COMPRESSION ---------------------- See accompanying document projects2000.doc. Investigation (1): If hardware is available - develop software algorithms. If hardware is not available - develop the hardware! Test the effectiveness of the compressor by adding controlled amounts of noise to a communications link, and performing a phonetically- balanced speech intelligibility test. Make measurements of mean power and peak/mean signal ratio with and without the compressor in-circuit. Measure the actual and the subjective increase in s/n ratio using the compressor. Investigation (2): Using the hardware as a level control, develop algorithms to perform radio AGC functions, together with click suppression, and 'holding time' (i.e. when signal disappears completely, gain is remembered for future use). Evaluate the algorithms in a simulated communications link in the presence of Gaussian and non- Gaussian noise. 12. LASER RANGEFINDER --------------------- Laser rangefinders are common devices now, but they are expensive. How close can a simple project approach the accuracy and repeatability of a commercial device? The rangefinders work by using a 'time-of-flight' measurement; but since light takes only 3.3ns to travel a metre measurement is difficult! A common design transmits a modulated signal, the receiver demodulates and down-shifts this, whilst preserving phase-shift. This magnifies the time-of-flight measurement by, typically 10,000 times. Investigation: find out how a laser rangefinder works and build a demonstration system. You will need a laser diode that can be modulated and a photodiode. Why will you not need any other optical components (e.g. lenses)? Evaluate the accuracy and repeatability of your rangefinder, especially with variations in the temperature of the components. Further work: Why is the repeatability of your rangefinder so poor? How can this be improved using an opto-mechanical system comprising a prism or mirror to chop the beams? Without building a full opto-mechanical system, make measurements to demonstrate the potential improvement. 13. ELECTRIC KETTLE SWITCH -------------------------- See accompanying document projects2000.doc. Typically, electric kettles make use of a bimetallic spring to switch off when steam, being generated at a high rate, indicates boiling. However, boiling water is too hot for making instant coffee, so a kettle that switches off at 70C would be better. (70C is the 'holding temperature' of Macdonald's coffee). This is a very simple project, but you can create all sorts of enhancements purely as a 'design exercise'. Investigation: Design a simple electronic switch that will turn a kettle off when it reaches 70C. The switch may be electronic (e.g. triac) or electromechanical (i.e. relay) but should be small enough to be glued to the back of the kettle's mains plug. This means that if you use low voltage electronics you will not be able to use a transformer. Further work: Design the unit to operate without its own switch. You will need to address the problem of what happens when 70C is reached. Will it maintain the water at 70C or switch the kettle off? Will it give an audible indication of temperature? How does the user signify that he wants the kettle actually to boil? This is probably a job for a microcontroller.