The hardware for the project was divided into six different sections:
Modules 1 through 5 were each constructed on their own circuit boards and connected to each other and the front panel using screw-down terminal blocks.
The circuit diagram for the control circuit is shown above. This circuit is used to control the pulse width modulation (PWM) signal sent to the buck and boost converters. It receives analog signals of output voltage and fuel cell current from other circuit boards. It also receives an analog signal from the front panel which sets the desired fuel cell current value.
Fuel Cell Current Sensing Module
The fuel cell interface circuit is used to measure the current flowing through the fuel cell and send the signal to the controller circuit. The schematic diagram for the fuel cell controller circuit is shown in the figure above.
Battery Bank Voltage and Current Sensing Module
The schematic diagram for the battery bank circuit is shown in the above figure. The battery bank circuit contains the circuitry to measure the battery bank voltage and current. It also contains a separate circuit to regulate the input voltage from the AC to DC wall adapter.
Buck Converter Circuit
The schematic diagram for the buck converter circuit is shown above.
Boost Converter Circuit
The figure above shows the slightly different arrangement of the components in the boost circuit.
There are four LEDís, a switch, and a potentiometer mounted on the front panel for status indication and user control. The top LED indicates when the control module is powered. The second LED from the top is illuminated when one of the converters is enabled. The third LED is used to indicate when the controller detects an over-voltage on the battery bank. The bottom LED lights up if the fuel cell current exceeds a fault threshold. The switch is used to start or stop converting; and the potentiometer sets the desired current for the fuel cell.