1. ME 102A Spring 2010 April 21, 2010 Jennifer Lew Stephen Tu

2.  Fans provide essential cooling to a computer  The fan’s rotational speed is directly related to its cooling capacity  Without properly calibrated fan, CPU would almost instantly melt CPU: http://hardforum.com/showthread.php?t=1423185http://hardforum.com/showthread.php?t=1423185 Fan Grid: http://forums.legitreviews.com/about12716.htmlhttp://forums.legitreviews.com/about12716.html

3.  Idea: Use fan blades as an Optical Encoder  By measuring the number of pulses in a fixed period of time, can determine speed of blades Rotary: http://hades.mech.northwestern.edu/index.php/Rotary_Encoderhttp://hades.mech.northwestern.edu/index.php/Rotary_Encoder Fan: http://computershopper.com/shoptalk/components/silverstone-fm83-cram-more-fan-into-the-same-spacehttp://computershopper.com/shoptalk/components/silverstone-fm83-cram-more-fan-into-the-same-space

4. 1. Fan  Voltage Supplied  Current Supplied  Impellers 2. Sensors  Infrared LED  Phototransistor  Circuit: Resistors, Voltage Supplied 3. LabVIEW VI  Input number of impellers  Implements GenerateCalibrationCurve()  Displays RPM, voltage supplied to fan 4. Error Analysis  Sensor is noisy, so must take many samples and consider confidence intervals Procedure for calibrating fan IR LED: http://www.solarbotics.com/assets/images/ir-led/ir-led_pl.jpghttp://www.solarbotics.com/assets/images/ir-led/ir-led_pl.jpg Phototransistor: http://farm3.static.flickr.com/2325/2105641666_1487ce594e.jpghttp://farm3.static.flickr.com/2325/2105641666_1487ce594e.jpg

5.  Issues  Current limit on power supply – data at higher voltage values not truly reflective of fan characteristics ▪ Will resolve by using analog lab equipment that does not impose as stringent current limits. ▪ However, this makes the UI less robust, due to less automation  Scheduling  Basic prototype implemented last week, but ran into the current issue above  4/26/2010: Have prototype finished, current issued resolved  4/30/2010: Have prototype tested for robustness, finish error analysis  5/3/2010: Present prototype to customers  5/7/2010: Turn in final report and give final presentation