The Project

While working on the micro plane project, I would often find CAD models for propellers online with the thrust it would provide as a function of the rpm. As I would often resize the models to better suit my target size, and out of interest in the challenge itself, I decided to design my own propeller thrust test rig.

The Design

Board Design

As I will be working with small motors, with low power requirements, I decided to design the circuit to be powered via USB. In an effort to improve my skills and simplify the circuit, rather than using a micro controller, I decided to use the FT232H IC. To control the voltage supplied to the motor I am using a buck regulator IC, and to measure the thrust a strain gauge along with the NAU7802 24 bit ADC for bridge sensors, finally I am measuring the current going through the motor by measuring the voltage drop across a small resistor. All of these components are connected to the FT232H via a I2C bus. The I2C bus also has its pins broken out to allow for future additions to the sensing circuit.

Prototyping

A prototype of the thrust test rig is shown below. I designed it with the motor elevated away from the surface the rig is placed on to avoid the influence of the ground effect on the thrust measurements. The rig was printed in my resin 3D printer, however, I feel that it is not rigid enough and will probably laser cut some MDF for the final rig. The circuit is only the force sensing component of the rig, which is read by an Arduino which displays the results on a graph, while I control the voltage supplied to the circuit with my DC power supply.