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TFHT01 - UAV Humidity and Temperature Sensor

Open Source Hardware Association Certificate Kicad

The TFHT01 hygrometer sensor offers flexible integration options. It can be directly connected to a Pixhawk autopilot with PX4 firmware, or it can be used as a sensor for the TF-ATMON monitoring system.

Sensors mounted on UAVs can be used for a variety of purposes. TFHT01 can measure air temperature and humidity, which can be used for meteorological purposes to estimate whether icing may form on aerodynamic surfaces. It could also be used to determine if the flight is conducted within the operating range of the drone. Another use can be to measure the temperature of selected UAV components, for example, the temperature of batteries, ESC, motor, or some bearings.

TFHT01A top view

Where to get it?

The TFHT01 is commercially available from ThunderFly s.r.o.. For a commercial quotation or support, contact us by email at [email protected] or shop at Tindie store.

Parameters

Parameter Value Description
Sensing element SHT35 Other possible sensors are SHT30 or SHT31
Typical accuracy 1.5 %RH and 0.1 °C
Repeatability 0.15 %RH , 0.08 °C The stated repeatability is 3 times the standard deviation (3σ) of multiple consecutive measurements at constant ambient conditions.
Operating temperature range 0 °C - +65 °C Sensor physically measures in range -40°C to +120°C with reduced accuracy
Operating humidity range 0-100 % At humidity above 80% the performance of the sensor could be degraded in case of prolonged periods
I2C connector 4-pin JST-GH The second connector could be installed on the opposite side
I2C address 0x44 default By switching of JP1 is possible change address to 0x45
Storage temperature range -20 °C - +40 °C
Operational input voltage 3.6 - 5.4V Overvoltage internally protected by zener diode
Mass 2 g PCB without cabling
Dimensions 30 x 15 x 6.5 mm PCB
Weather resistance IP40 External connectors fully occupied. The sensor itself could be protected by IP67 according the sensirion datasheet

Applications

Atmospheric sounding

The TFHT01 sensor could be used for direct atmospheric sounding. Here is an example of measured data taken by TF-G2 autogyro.

TFHT01A atmospheric profiling

Design

TFHT01A top view

Schematics

Schematics

Usage in PX4 autopilot firmware

The PX4 autopilot firmware supports the sensor. Multiple sensors can be connected to one autopilot. The measured data are immediately sent to the ground station and they are also logged in the onboard ulog file. Sensor support can be enabled by setting the SENS_EN_SHT3X parameter to 1.

Driver Commands Examples

CLI usage example:

sht3x start -X

Start the sensor driver on the external bus

sht3x status

Print driver status

sht3x values

Print the last measured values

sht3x reset

Reinitialize senzor, reset flags

PX4 Driver Usage

sht3x <command> [arguments...]
 Commands:
   start
     [-I]        Internal I2C bus(es)
     [-X]        External I2C bus(es)
     [-b <val>]  board-specific bus (default=all) (external SPI: n-th bus
                 (default=1))
     [-f <val>]  bus frequency in kHz
     [-q]        quiet startup (no message if no device found)
     [-a <val>]  I2C address
                 default: 68
     [-k]        If initialization (probing) fails, keep retrying periodically

   stop

   status        print status info

   values        Print actual data

   reset         Reinitialize sensor

Usage in Ardupilot firmware

In the Ardupilot firmware, the corresponding sht3x driver for TFHT01 is currently missing. The contributions are welcomed.

Resources