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68 lines
4.1 KiB
Markdown
68 lines
4.1 KiB
Markdown
# TFSLOT - Venturi effect airspeed sensor
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[TFSLOT](https://github.com/ThunderFly-aerospace/TFSLOT01) is an open-source airspeed sensor based on the [Venturi effect](https://en.wikipedia.org/wiki/Venturi_effect) that also has an IMU.
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[TFSLOT](https://github.com/ThunderFly-aerospace/TFSLOT01) is an airspeed sensor based on venturi effects.
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In the basic configuration, the TFSLOT is equipped with the [TFASPDIMU02](https://github.com/ThunderFly-aerospace/TFASPDIMU02) sensor board, which contains a differential pressure sensor ([Sensirion SDP3x series](https://sensirion.com/products/catalog/?filter_series=d1816d53-f5c8-47e3-ab47-818c3fd54259)) and a 9-axis motion tracking sensor ([ICM-20948](https://invensense.tdk.com/products/motion-tracking/9-axis/icm-20948/)).
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The IMU unit can be used as an external compass.
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- This design brings several advantages when used on small-scale and slow-flying UAVs.
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- Better resolution at low airspeeds (below 10 m/s).
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- Configurable sensitivity brought by changing the profile.
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- Less tendency to clogging (For example, by clay after landing)
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- Weatherproof (rain, snow, etc.)
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- Direct differential pressure sensor integration without any additional tubing.
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Less chance of sensor malfunction.
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- Possibility of direct integration into the construction of the drone.
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Design is fully open source.
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- Integrated external IMU unit.
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Thanks to the printed tube, it is very easy to change the measuring profile and thus to change the sensitivity in certain speed ranges.
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In the basic form, it is optimized so that the measured differential pressure corresponds to the pressure from the pitot tube.
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_First integration of TFSLOT into [TF-G2](https://github.com/ThunderFly-aerospace/TF-G2/) autogyro_
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::: info
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Full documentation and source files can be found on [GitHub](https://github.com/ThunderFly-aerospace/TFSLOT01).
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:::
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## 구매처
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TFSLOT is possible to buy at [Tindie store](https://www.tindie.com/products/thunderfly/tfslot01a-inovative-drone-airspeed-sensor/) or by sending us an inquiry via email at info@thunderfly.cz
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## 연결
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[TFASPDIMU02](https://github.com/ThunderFly-aerospace/TFASPDIMU02) is equipped with I2C JST-GH connector, which conforms to the pinout of the [dronecode standard](https://github.com/pixhawk/Pixhawk-Standards/blob/master/DS-009%20Pixhawk%20Connector%20Standard.pdf).
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Therefore the sensor can be connected directly to an I2C port of autopilot using an I2C 4pin JST-GH cable.
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## 설정
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Because there is an [IMU IC](https://invensense.tdk.com/products/motion-tracking/9-axis/icm-20948/) connected in front of the sensor, the IMU IC needs to be set into a bridge mode.
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Following this the airspeed sensor driver can be run. This can be done using the following command sequences. The commands assume a connection to I2C2 port.
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```sh
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icm20948_i2c_passthrough start -X -b 2 -a 0x68
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sdp3x_airspeed start -X -b 2
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```
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This sequence can be stored on the SD card in the `/etc/config.txt file`.
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You can read more about the configuration on the SD card on a [separate page](../concept/system_startup.md#replacing-the-system-startup).
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Because the conversion of differential pressure to airspeed differs from the Pitot tube, this profile needs to be changed.
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This is done by setting parameter [`CAL_AIR_CMODEL`](../advanced_config/parameter_reference.md#CAL_AIR_CMODEL) to 3 (Venturi effect based airspeed sensor)
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## Calibration
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Calibration is a bit difficult because the current firmware version does not support calibration with negative values.
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Because the used sensor measures both airflow directions symmetrically and has zero offset, there is no need to calibrate repeatedly before every takeoff.
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But you have to ensure that there is no airflow during the calibration process.
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The easiest way to do the calibration is to take the adhesive tape and tape it between the pressure inlets to the sensor.
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Then start the calibration process and blow from the back when prompted.
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If the pressure of at least 50 Pa is created, the calibration will be successful.
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