final year projects

Infinitly variable controller for furnaces. An device used to match heat input to heat loss so that the furnace operates at near constant output changing input only as the heating loss or gain changes. No more on and off. The thermostat would be set at the target temperature. Perhaps generating a digital signal. The ambient temperature (room temperature) would also generate a digital signal. A comparator circuit would compare the target temperature against the ambient temperature. As the furnace produced heat the temperature between the target temperature and ambient would start to decrease. As the comparator circuit read this closure it would start to ramp down the power to the furnace fan and heating coil. As the power ramped down it would start to match the heat loss and the furnace would then be putting heat into the house at the same rate it was being lost. There are a number of reasons why this would be desirable. The fan and heating coils could be made smaller. The electricity demand would be less variable. The ramp down function of the heating coil could probably be linear but the fan power would not be. If I could design the circuit I would probably have the heater coil power change as a linear function of the temperature gradient and the fan as a square relationship. I would have the system ramped to full power if the temperature gradient was more than 5 degrees. I would make the power infinitley variable between max and off. Not a series of switches but a smooth variability between max power and off.

Art:

An fun lab project would be to use a long coil, cover it with solar cells to power the coil, a polarity reversing switching circuit, LED, a photo sensor tuned to the frequency of the LED, a small mirror, and a very low friction bearing. Imagine the coil as the pointer of a magnetic compass. Mount the LED along some point along the length of the coil so that it will pass over the mirror at the point in coil rotation at the magnetic equilibrium condition (North, South, North South) where the light of the led will be reflected onto the photo sensor triggering the polarity reversing switch. Balance Mount the package on the low friction bearing. Align the package North, North, South, South relative to the geo-field and let it go. As it begins to turn to align North,South, North, South, the energy from the solar cells will be converted to the rotational energy of the coil turning. As the coil moves towards the magnetic equilibrium position the rotational energy will carry it through the point of magnetic equilibrium polarity at which time the led passes over the mirror, reflected into the photo sensor, activating the polarity reversing switch, and further accelerating the process. Hopefully it will go round and round and round, faster and faster until the power from the solar cells are equal to the power loss due to the dynamic drag of the system. At what relative field angle would the power flowing in the circuit be greatest? At what relative field angle would it be at a minimum? Could the power be calculated as a function of coil acceleration, bearing and aerodynamic drag? Could the bearing drag be derived as a function of coil acceleration, circuit power, and aerodynamic drag?