Project Design

Flow Chart: A graphical description of our functional Alarm System

Basic schematic drawing of the P-1.00 System

Custom Hardware #1 Additional Buttons for Keypad Extra Buttons, essentially a keypad, were required so that the alarm system could be activated and deactivated when needed. The design is very simple and easily implimented. The following is a schematic for the keypad (figure1). Note: Originally we planned on using a matrix-based keypad. However, due to time constraint and inadequate experience, a simpler keypad was used.

R0=R1=R2=R3=R4=R5=R6=10K Ohms

Function of Equipment: * The LED indicated to the user that the keypad has been turned on. * R[0...5] allow for the internal capacitance of the push buttons used to discharge so a clean logic zero can be produced. * R6 is used to decreas the current going through the LED so it won't burn out. It also prevents the positive lead from being connected directly through ground, which would cause unwanted effects. 10k Ohm resistors were used since the resistors used for the onboard buttons and LED on the FPGA board are also 10k Ohms.

Figure 1a (above) shows the original "matrix" keypad. We opted not to choose this method, but researched it in case we wanted more buttons. More buttons would lead to more possible combinations and thus a more secure system. See Discussions and Conclusions for more details.

Custom Hardware #2 Circuitry Required to Connect Motion Sensor to FPGA Board The purpose of this circuit is to transmit signals between circuits of different potentials and impedances. This circuit ensures that a square wave signal at a safe voltage and impedance are sent to the FPGA board so no damage is done to the board. The main device used is an opto isolator (figure 2).

R1 = 270 Ohms R2 = R3 = (6V-1.2V)/10mA = 480 Ohms10k Ohms R4 = 10k Ohms C1 = internal capacitance of the adaptor Function of Equipment: * R1 is used to discharge the capacitor once the 120V AC to 5V DC switches off. This resistor value was determined by trial and error. A large resistor value increased the time required to discharge the capacitor and small resistors caused the 1/4 watt resistors to overheat. * R2 is used to decrease the current and voltage going through the LED. The LED also indicates the operation of the motion sonsor. A 10k Ohm resistor was used since it is the standard value resistor used in series with an LED. - When the motion sensor is on, the LED is on - When the motion sensor is off, the LED is off. * R3 is used to decrease the current going through the LED in the photocoupler (opto isolator) so it doesn't burn out. * R4 is used to discharge the floating capacitance in the internal circuitry of the photocoupler. The size of the resistor was not important in this case as any capacitor value could have been used since the speed at which the photocoupler responds is not very important. A 10k Ohm resistor was used since it is the standard resistor value used in this type of application. * The 74HCT14 hex inverter is used to clean up the signal being sent from the opto isolator so it is CMOS compatible.

Introduction User's Manual Code Listing Discussion and Conclusions Team Members