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Students are welcome to suggest their own projects.

Available if not labelled TAKEN

Chaos in repetitively triggered multivibrator circuits

Careful measurements are made of the chaotic time series of triggering of a monostable multivibrator, when it has not had sufficient time to recover the charge on the timing capacitor.

Electricity watt-hour datalogger


This project makes mains plug-in modules which measure the total watt-hours drawn by an appliance. It is then possible to transmit this information to a local computer using bluetooth technology. The device needs a plug, socket, data acquisition circuitry and a local memory. Alternatively the data can be stored locally for readout using a memory stick or equivalent technology and there is the option of a display for visual inspection.

High Q factor tuned circuits

The student constructs a tuned circuit at 5 MHz having the highest possible measured Q-factor. Methods of coupling energy to and from the tuned circuit are investigated. Temperature stability is investigated. Various construction techniques are compared.

Three-dimensional vector length detector


This project is part of a system to construct chaotic circuits which have traps which are entered very infrequently, at indeterminate times, but with absolute certainty, to model irregular processes in real-world systems.

This circuit takes three analogue inputs, converts them to digital format with 8 bit ADCs, squares and adds them, takes the square root of the sum, and reconverts via 8 bit DAC to an analog output. A comparator gives a binary output when the analogue vector length exceeds a certain threshold.

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Radio controlled clock

This project takes an off-air radio signal and uses it to control a special clock, that has only five divisions between 00:00GMT and 12:00GMT, and runs backwards. The long hand goes round five times anticlockwise in a 12 hour time period; the face has equally spaced divisions which divide this 12 hour span into 2.4 hour chunks, but otherwise the clock is normal. It uses a stepper motor driven by appropriately-timed pulses. The short hand goes round two revolutions per day, in the usual way, but backwards.

Data wand


A linear array of red LEDs is mounted on a wand and lit sequentially so that text is seen due to the persistence of vision, when the observer looks at the wand when it is being waved back and forth. Accelerometers detect the speed of the wand and the direction of motion, and alter the interval and sequence of illumination to provide continuous text display as the wand is waved. The words displayed change every two waves of the wand.

Ultrasonic data communications between neighbours using the household water supply.

This idea is for secure short range ultrasonic data communications between close-spaced houses in a street, by bolting transducers onto the incoming rising cold water main. The student investigates the link budget and the practical aspects of this scheme, and determines a specification and constructs a demonstrator.

RS232 wireless unidirectional computer link


RS232 RF carrier wireless LAN link The objective is to construct an RS232 serial link between PCs using no wires, can be RF carrier or acoustic or optical link.

Acoustic vehicle-speed measurement method


The sound of a passing vehicle is captured and analysed using signal processing techniques to extract the doppler shift in the predominant frequencies, from which the vehicle speed may be estimated.

My initial calculations give the following.

If the ratio of approaching vehicle pitch (frequency) to departing vehicle
pitch (frequency) is U

AND the air is dry and at 20C and at normal atmospheric pressure
(you are at sea level)

Then the velocity if the vehicle is 772*(U-1)/(U+1)

I've just heard a motor bike go past and the pitch drop by a minor
third (musical) which is three semitones; each semitone has frequency
ratio 2^(1/12) because there are 12 semitones per octave and an octave
is doubling in frequency

So the frequency ratio is 2^(1/4) or 1.19 approx (19% drop in frequency)
and the velocity 67 mph.

The speed limit here is 30. One only hears the faster vehicles,
because they make much more noise.

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MSF Rugby standard frequency recovery circuit.


This uses a PLL to recover the 60kHz MSF carrier and strip off the modulations and carrier dropout to give a display on a frequency meter accurate to 8 digits. It can be used for calibration of frequency meter crystal oscillators.

Bluetooth message interface


Bluetooth technology is used to pass a message (possibly scrolling continuously) from a PC to a display which may be wall-mounted for example.

Zagi antenna construction and measurements

A zagi antenna is made from serrated wire or plate. It has reduced length dimension because of the slow wave characteristics of the periodic structure. The student is asked to construct and measure a Zagi for the 225MHz digital broadcast band in the UK.

D.Jefferies email
19th September 2005.