wind_sensor:meeting_minutes_may_19_2017

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wind_sensor:meeting_minutes_may_19_2017 [2017/05/20 01:12]
mwu [Ultrasonic Wind Sensor]
wind_sensor:meeting_minutes_may_19_2017 [2021/09/19 21:59] (current)
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       * The trigger'​s threshold levels were experimentally determined to be: Vth = 1.95V, Vtl = 1.15V. The idea was to center the signal at one of the thresholds and use the other threshold as the trigger. This would'​ve solved the issue since the signal would have to satisfy one threshold before it changes the output of the trigger (qualification).       * The trigger'​s threshold levels were experimentally determined to be: Vth = 1.95V, Vtl = 1.15V. The idea was to center the signal at one of the thresholds and use the other threshold as the trigger. This would'​ve solved the issue since the signal would have to satisfy one threshold before it changes the output of the trigger (qualification).
       * The signal was centered at 1.95V, but the result was inconsistent. Sometimes the signal would register while other times it wouldn'​t.       * The signal was centered at 1.95V, but the result was inconsistent. Sometimes the signal would register while other times it wouldn'​t.
 +    * Since the Schmitt Trigger didn't work out, we did a bit of research to see if we could add hysteresis to our LM339 voltage comparator. We could and we did, and the results were more consistent.
 +      * This worked okay, but the results we obtained were not as consistent as we would'​ve liked (~1 us variance). After observing the output of the LM339 chip with hysteresis on the oscilloscope,​ we discovered that the time of transition changes by a period or so. We need to investigate this further to improve the consistency of the triggering.
   * To Do:   * To Do:
 +    * Test reducing ringing by sending half-period shifted pulses after the initial set of pulses.
 +    * Investigate how to improve the reliability of the LM339 with hysteresis triggering mechanism.
 +    * Conduct tests with fans and add in calculation of the wind speed into the program so it can print out the derived wind speed directly onto the console.
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