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Interface Board

Since team 6 decided to use a microcontroller it was necessary to use an interface board to relay the commands from the microcontroller to the solenoid valves. An interface board is required for several reasons, mainly that the solenoid valves operate at a different voltage and to prevent interference from the solenoid valves from damaging the microcontroller. As mentioned above, the microcontroller can only create output signals of 5V with very low current whereas the solenoid valves require 24V with a current of 400 mAh to operate. It is also possible that if the electrical systems for the microcontroller and the solenoid valves were to be directly connected that the power spikes and back emf created when the solenoid valves cycle on and off could damage the microcontroller since it is designed to operate on a highly regulated power supply.

            Four relay switches make up the core of the interface board. Relay switches allow a low powered signal to switch a much stronger power supply on or off without requiring the signals to interact directly. They accomplish this by using the smaller control signal to energize a magnetic coil to force one end of a magnetic metal connector to switch back and forth between two terminals while its other end remains anchored to a terminal of the opposite polarity. In the relay switches used to build the interface board a small spring is used to keep the switch locked in the off position while the coil is not energized; once the coil is energized by a signal from the microcontroller the relay switches the power for solenoid valve to “on” instantaneously. While there are several other electrical components that were used to build the interface board they are minor elements that were mainly used to condition the power and the control signal used to trigger the relay switch.