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wind_sensor:meeting_minutes_apr_7_2017 [2017/04/08 10:08] akim [Ultrasonic Wind Sensor] |
wind_sensor:meeting_minutes_apr_7_2017 [2021/09/19 21:59] (current) |
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| =====Acoustic Wind Sensor===== | =====Acoustic Wind Sensor===== | ||
| * Updates: | * Updates: | ||
| + | * Created a perforated board to mimic the traces on the pcb | ||
| + | * Single microphone test results were consistent for all four microphones. | ||
| + | * Conducted single microphone tests for all four microphones using several different fans and iterations | ||
| + | * Devised a method of collecting raw analog data for four microphones | ||
| + | * Collected raw data for all four microphones under 9 different fan settings repeated 3 times each. | ||
| * To Do: | * To Do: | ||
| + | * Analyze raw data results and real time processed results from single-microphone peak detector | ||
| =====Ultrasonic Wind Sensor===== | =====Ultrasonic Wind Sensor===== | ||
| * Updates: | * Updates: | ||
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| * We were also concerned with the current draw of the transducer. The Teensy can only safely output about 20mA of current. We weren't sure how to directly measure the current draw of the transducer, so we designed an experiment to calculate it. | * We were also concerned with the current draw of the transducer. The Teensy can only safely output about 20mA of current. We weren't sure how to directly measure the current draw of the transducer, so we designed an experiment to calculate it. | ||
| * Our results showed that at 40kHz, the transducer had an impedance of around 1.7k. Given that we are driving it with 3.3V, that puts our current draw to around 2mA, which is ten times smaller than our current limit. | * Our results showed that at 40kHz, the transducer had an impedance of around 1.7k. Given that we are driving it with 3.3V, that puts our current draw to around 2mA, which is ten times smaller than our current limit. | ||
| - | * Experimented with sending pulses with the Teensy and observed the response on the oscilloscope. | + | * Experimented with sending bursts of 41.67kHz pulses with the Teensy and observed the response on the oscilloscope. Below is the response of sending ten response, and below that is the response of sending a hundred pulses with a short delay. |
| - | * Sent 100 periods of a 41.67 kHz square wave followed by a delay. We observed that the receiver takes some time to "ramp up" to a distinguishable voltage and it also takes some time to "ramp down" after the signals have passed. | + | * {{ :wind_sensor:pulse-response.jpg?direct&600 |}} |
| + | * {{ :wind_sensor:big-pulse-response.jpg?direct&600 |}} | ||
| + | * We observed that the receiver takes some time to "ramp up" to a distinguishable voltage and it also takes some time to "ramp down" after the signals have passed. | ||
| * This ramping up and down may cause some issues when we're trying to determine our propagation time. We shouldn't rely solely on our threshold detector to measure the propagation time since the "ramp up" part of the response is unreliable. | * This ramping up and down may cause some issues when we're trying to determine our propagation time. We shouldn't rely solely on our threshold detector to measure the propagation time since the "ramp up" part of the response is unreliable. | ||
| * A smarter way would be to estimate the possible propagation times and to either discard a received pulse if it is too early, or too late. We can do this because we know the temperature and distance, so we know the propagation time with no wind. Then, we can choose a max and min wind speed to get our max and min propagation times, which we'll use to make sure our measured propagation times are within the boundaries. | * A smarter way would be to estimate the possible propagation times and to either discard a received pulse if it is too early, or too late. We can do this because we know the temperature and distance, so we know the propagation time with no wind. Then, we can choose a max and min wind speed to get our max and min propagation times, which we'll use to make sure our measured propagation times are within the boundaries. | ||