The first project of my mechatronics education was to build a automated bridge with only two button and an emergency lowering of the bridge in case of high winds. The buttons where used for giving a up and a down command or if both buttons where pressed for an emergency stop. I used the following components for the bridge:
- Two Arduino’s, for the processing of the data
- H-bridge, for two direction motor control
- 3 buttons, I added a dedicated emergency stop
- Fan, for measuring the wind
- Op-Amp, boosting the fans signal
- MPU6050, for measuring the bridges angle
- SSD1306 OLED-display, display the position of the bridge
- Two servo’s, for the barriers
- 555-timer circuit, for the warning lights
- Opto-coupler circuit
- Low-Pass filter
- Lineair voltage regulators
Although the bridge worked according to plan it was an over-complicated mess .This included the use of an Op-Amp for boosting the voltage of the “wind meter”.
The use of two Arduino’s because one Uno did not have enough memory to run the complete code. And for the communication between the two Arduino’s I used three ‘three state bits’. This was done bu using PWM signals with a Low-Pass filter to stabilize the ‘second state’ enough so the second Arduino would measure this correctly with it’s analog input. The second Arduino would receive a low, middle or high signal on three inputs so was capable of receiving nine different states. These nine different states would correspond to nine different pictures on the display.
Measuring of the bridges angle was done by using a 6 DOF MPU6050 and using the accelerometer data to calculate the angle. The acceleration of the bridge was only partial compensated by averaging five consecutive data samples.
An Optop-coupler circuit was also needed due to the motor interfering with the I2C used by the MPU6050.