Principle of Operation

            A planned block diagram of our Electronic Dartboard is displayed in Figure 1. Our block diagram is separated into 3 sections: sensing electronics, micro-processing unit, and a graphical user interface.

            The green color block in the system block diagram is our electronic hardware. This is mainly for our sensing implementation and external components. The yellow colored block describes the function of our microprocessor. This is mainly for storing and transmitting values. The orange block is our GUI. This is the computer program that displays the score.

            The principle of operation is to display a value to the screen when a dart hits the dartboard. The key idea to making this work, is how to recognize when the dart hits the dartboard. The plan to making this work is to use sensing devices, mainly consisting of pressure sensors. As soon as a sensor detects a dart, it is able to send a voltage to the microprocessor. The microprocessor is then able to relay a value from the voltage and will send the value to the computer to display.

            When the unit is switched on, voltage is sent to all electronic components, powering them up. All sensors will be held at a constant voltage and all microprocessors will be reset. The GUI interface will also need to be initialized. As a dart hits the dartboard, a sensor is able to recognize where the dart landed. As the sensor is activated, a voltage is sent to one of the inputs of the microprocessor. As the microprocessor receives a voltage from a specific input, it will relay this into a value. This value is then sent to the computer through a serial line. The transmitted value will then be displayed on the user interface.

Specification of the Blocks

            There are a total of 12 blocks in our system block diagram for the Electronic Dartboard. We have different colored areas indicating the major sections. We are going to use sensing options for the green areas, which is mainly our hardware. The microprocessor, contained in the yellow block, will be used to store and transmit data.  The graphical user interface in the orange area will be used to display score.

Pressure Sensor Block

            The function of this block is to determine when a dart hits the dartboard. We will be using a mixture of 3 different types of sensors: piezoelectric sensor, strain gauge, and pushbutton sensor.

1. Piezoelectric sensors: the kinetic energy from the dart will be transferred to the dartboard, which in turn will be transferred to the piezoelectric tab, mounted to the back of the board.  Depending on how far the piezoelectric tab is deflected, it will induce a certain voltage.  A 2mm deflection will a 7V output.  A 90 degree bend may produce up to 70V output.  This voltage will then be regulated to the appropriate level to be transmitted to the PIC.

2. Strain gauge: the kinetic energy from the dart will be transferred to the dartboard, causing momentary deformation. This in turn will bend the strain gauge and cause it to increase its resistance. We will use a resistor network, consisting of 3 resistors and the strain gauge itself. They will all start with the same resistor values. 2 of the resistors will be in series, the other resistor and strain gauge will be in series. A constant voltage will be sent to both of these stages and then will be connected to ground. The resistors and voltage will be chosen to create 5 or 15 volts in the center of the two stages. Those two voltages will then be sent into a NAND gate. When the strain gauge is bent, it will increase its resistance, causing a difference in voltage between the two centers. The NAND gate will detect the different values and will send a 5 or 15 volt signal to the PIC.

3. Pushbutton sensor: the pushbutton will be powered through 5 or 15 volts. As a dart hits a section on the dartboard, it will cause the section to move in and activate the switch on top of the pushbutton. As this happens, the pushbutton is turned on, and will allow voltage to flow through. This will deliver a 5 or 15 volt signal to an input of the microprocessor.

Foot Line Sensor Block

            This is a foot pedal on top of a pushbutton. 5 or 15 volts will power the pushbutton. When the pedal is depressed, it will trigger the pushbutton, sending a voltage signal to the microprocessor, enabling it to accept inputs.

Store Data Block

            A voltage is received in one of the input ports of the microprocessor. The signal is stored in the working register and then saved into its own register.

Compute Data Block

            Through the PIC programming, the taken in and stored in a register will be convert to ASCII.

Transmit Data Block

            The computed ASCII value will be sent to the computer through a serial connection.

Store Data Block (GUI)

            The ASCII value from the serial line, will be taken in and stored accordingly.

Compute Data Block (GUI)

            The stored data will be computed and displayed as an integer, according to the stored ASCII value(s).

Display Scores With GUI Block

            Displays score with GUI.

Reset Block

            There is a reset button on the GUI that will reset the computer program and send a reset signal to the microprocessors, clearing out all the data.

AC/DC Converter Block

            This will convert 120 V AC into 5 or 15 V DC to be used with our Electronic Dartboard.