Control of the SADCAT’s
The microcontroller will be employed to control the descent and surfacing of the SADCAT’s system by controlling a series of three solenoids. The pressure data that the stamp is collecting and saving in memory will be used to time when the solenoid configuration will change to control the descent and ascent of the system. When the SADCAT’s is ready to descend, it jumps into the descent algorithm and will open the two solenoids that will allow the water in the ballast and allow air to leave the ballast. When this happens the stamp will be put into the descent software loop that checks the pressure sensor every 5 seconds and then check it against the last pressure reading to assure that the descent has not become faster than the specified rate of descent which will be 1 ft/sec. If the descent hasn’t become more than 1 ft/sec it will continue to allow more water into the ballast but if it is faster than the desired rate of descent it will stop allowing water into the ballast and change the configuration of the solenoids to allow the compressed air into the ballast to slow its rate of descent. This will continue until the pressure reading reaches its preset max that will be determined prior to the start of the SADCAT’s mission. Once it has reached its maximum depth it will then jump into the surfacing algorithm that will control its ascent back to the surface. The ascent of the SADCAT’s will be controlled in the same way that the descent algorithm controlled its sinking rate but will allow for it to rise at 2 ft/sec. Once the pressure sensor reads that the pressure has again become what the team has determined to be atmospheric it will then close all the solenoids and then jump into a GPS loop. The GPS loop will use the GPS to determine when it has traveled a defined distance away from the last dive and when it has determined this it will repeat diving and surfacing process. During this time the radio will also transmit the data that was collected from the dive to a remote location. The GPS will compare the coordinates that it surfaces at with the coordinates to where it has moved to. As a safety measure there will also be a timer that will only allow the diving and surfacing algorithms to last a certain amount of time and if it hasn’t completed this sequence in the allotted time it will automatically change the solenoid configuration to surface the SADCAT’s.
The power will be supplied by a 12 Volt gel-cell battery that has a 7 AH rating. The stamp draws 15mA when it is on and will be used the entire time. The solenoids are opened and closed using 12 Volts and they draw .63 Amps each when they are being held open. The pressure sensor runs on 5 volts that is pulled off a pin on the board and draws minimal current when in use. The temperature sensor has already been integrated onto the board and runs off the board’s power and also only draws minimal current when it’s on. The radio will be used at its 50 Watt power setting and it will draw 4 amps but it will only transmit for approximately 10 seconds. The GPS will draw 15mA of current off the board when it is transmitting its location.