Electronic Design for System

This project uses a Raspberry Pi as a central computer with added electronics designed to process the generated voltage input and output the PWM signal.

Block Diagram

The input generated voltage from the DC Motor is really small (in the mV range). Therefore, an op-amp (Operational Amplifier) is added to amplify the signal. The Raspberry Pi does not read analog input signals, thus a 12-bit ADC (Analogue-to-Digital Converter) with 4 channels (ADS1015) is used to read the input voltage signal using the I2C communication bus. Depending on the input voltage readings obtained from the generator, a Pulse-Width-Modulation (PWM) control signal is sent to the servo motor which controls the blade pitch. This is done to keep the generator within proper operating limits.

The ASD1015 was chosen as it is supported by the Raspberry Pi kernel out of the box and therefore does not require any additional measures to make it compatible.

Schematic Diagram

From this schematic could be generate the PCB board shown in the following figure.

Circuit

The specifications of ADS1015 which has been chosen to convert signal will be provided in the table 1.

Table 1: Specifications of ADS1015 and the recommendded operating conditions

Feature	Pins	Min/Reccommendded	Max/Reccommendded	Unit
Power-supply voltage	VDD to GND	-3 / 2	7 / 5.5	V
Analog input voltage	AIN0, AIN1, AIN2, AIN3	GND-0.3 / ±0.256	VDD+0.3 / ±6.144	V
Digital input voltage	SDA, SCL, ADDR, ALERT/RDY	GND-0.3 / GND	5.5 / 5.5	V
Input current, continuous	Any pin ecept power supply pins	-10	10	mA

(Adapted from TEXAS INSTRUMENTS)

At first ADS1015 was expected to receive analog voltage alone from the wind turbine model which is quite small, however, the result after it has been tested is not as the expectation. Therefore, it requires an amplifier to increase the signal amplitude.

The LM324 was chosen as the op-amp, as we needed something compatible with the 5V single rail supply and the university stores only had this one in stock suitable for our criteria. This is why we have a quad op-amp package and use only one. There are of course devices better suited to the application, but the easy availability made this the preferable choice.

Datasheets:

• ADS1015
• LM324