1. Frozen Precipitation Detector for SODAR Systems Dec1006 Abstract Atmospheric Systems Corporation (ASC) produces the Sonic Detection and Ranging (SODAR) system used to determine wind speed and wind direction of the atmosphere up to 200 meters. The instrument is used in the wind industry to measure wind shear conditions at potential wind project sites. The SODAR produces an audible beep at a very specific frequency, and then listens for the reflection of sound waves from aerosols in the atmosphere. Using the Doppler shift of the returning signals, the SODAR can determines wind speed and direction. The SODAR uses a phased array of speakers built into an enclosure which helps shape the sound direction. The enclosure acts as an antenna to shape the outgoing sound waves and collect the returning signals. System Diagram Problem During the SODAR operation, it is important that the reflector pad remains clear of debris. Snow collection on the reflector pad can impair the SODAR operation. A heater is built into the antenna to melt snow. However, the heater is very power-intensive and should only be used when snow is present system. Currently, the unit operates with a sensor that determines the presence of precipitation and freezing conditions. This sensor can report many “false positives” where sensor conditions are met, but heating is not needed. This leads to increased fuel usage and prolonged downtime (due to running out of fuel). A new solution should be devised to turn on the heater only when necessary. Design Solution Piezoelectric sensors will be used to detect snow that accumulate on the heating pad. These sensors will make use of the signals generated from the SODAR to tell the difference when there is snow on the sensors or not. When snow is present on the sensor, the voltage being read will be less than the voltage when the reflector pad is clear. The heater will only be turned on when the piezoelectric sensors has snow on them along with the readings from the temperature sensors. The solution circuit that incorporated amplifiers, sample-and-hold circuits and filters will be powered by the power source from the equipment. OR gates are included to fool- proof the piezoelectric sensors while an AND gate is used to determine heater operation. Requirements The solution must: be compatible with the current system. be powered by the solar panels on the equipment. use less power than the current detector. be able to function during extreme weather conditions. must only be on when there is frozen precipitation on the heating pad. must be able to take inputs from the temperature sensor as well to turn on the heating pad. know when to turn on the heater Testing Summary The testing shows that with a exposed reflector pad,the piezoelectric sensors generate around 100 millivolts and with any sort of debris, the sensors generate a lower voltage. This is used to differentiate between a clear reflector pad and a covered reflector pad. ASC can used this solution as a more efficient way to detect any frozen precipitation on the reflector pad. Snow accumulation on the heating pad can cause distortion to the sound reflections. Team Members Ashor Chirackal (EE) Imran Butt (EE) Luke Lehman (EE) Michelle Tan (EE) Website http://seniord.ece.iastate.edu/dec1006 Faculty Advisor Professor Timothy Bigelow Client Mr. Josh Underwood Output from the piezoelectric sensors. The frequency detected is 4.5KHz as from the SODAR. Output after feeding the readings from the piezoelectric sensors into the circuit. After noise was filtered, the frequency detected is 4.5KHz as from the SODAR Testing setup in the lab.Testing setup with the equipment.