Remote Touchscreen-Controlled Defense Turret Senior Design Documentation Courtney Mann, Brad Clymer, Szu-yu Huang Group 11
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Wireless communication
As mentioned before, the group is expecting massive analog data that will be transmitted from the camera to the user interface. After deliberating, it was decided to use wireless USB as the protocol between those two nodes. Wireless USB is the easiest, and the most sufficient wireless technology that the group has found. Its “plug and play” scenario will save some hassle programming it. Wireless USB is capable of sending 480Mbps at distance up to 3 meters and 110Mbps at a distance up to 10 meters. In order for those two ends to talk to each other, it is necessary to make sure the tablet has the software that would recognize the USB protocol, which will not be a problem since almost all of the tablets in the market have this feature built in. If not, wireless USB provides free software that can be downloaded from its website to connect those two nodes.
The protocol between the user interface and Arduino that the group decided to use is MRF24WB0MA RF transceiver module from Microchip. This module is certified IEEE 02.11 Wi-Fi radio transceiver module. MRF24WB0MA has an integrated PCB antenna, matching circuitry, and supports Wi-Fi with the free TCP/IP protocol stack. It can connect to the Arduino board simply using SPI interface and is an ideal solution for a low-power, low data rate Wi-Fi sensor network. This module has several power states that reduce overall power consumption. These states are hibernate, sleep, and active (two sub-states). These are detailed further in Table 11, given below. There is also a standby state that is not user-controlled. Because the whole system is operated in real time manner, the time required for the module to switch from one state to another becomes crucial. In order to design the PCB board properly for the project, the team had to know the digital electrical characteristics of this module. Width of trace is determined by the current that flows in the circuitry. To sum the total current, electrical characteristics of each electronic unit that will be implemented in the PCB board had to be known. See Figure 21 and Table 12 below for the detailed module specification. Table : Power State Definitions from Microchip 
Figure : Required Time to Switch States from Microchip Table : Digital Characteristics from Microchip 
To have the two nodes communicating to each other, both Wi-Fi network settings need to be set to Ad-hoc. Using a Wi-Fi protocol has one advantage, that is, no line of sight is needed so it is not a concern if there is any intrusion between those two nodes. To set up the protocol, the MRF24WB0MA is going to be embedded on the PCB board connect to Arduino. The task of connecting the Wi-Fi module to the Arduino is really simple. Only the SPI interface and the power and reset need to be connected, using 8 wires total. Figure 22 shows the detail of the connections. 
Figure : Microcontroller to the Wi-Fi module Interface from Microchip
In the scenario that a paintball gun is implemented as the firing device, it is necessary to include a rangefinder, so that the trajectory of the the paintball pellet will terminate at the center of the target. The range finding system that has been chosen, as described above in Research section 3.2.1, is the laser pointer and image sensor system. The laser pointer that will be used is the Instapark® Green Laser Pointer, which comes with multiple tips in different geometric patterns. The crosshair tip will aid in pinpointing the exact spot on the target, reducing the uncertainty caused by a larger area of light. The image sensor chosen for the project is the ELIS-1024A from Panasonic, a 1024x1 linear image sensor that adequately fits the specifications. The high resolution should provide relatively accurate results. Since the sensor measures only one pixel in width, it must be aligned perfectly with the laser pointer so that it sees the light, such that the laser is parallel to the optical axis of the sensor. This precision is important for the effectiveness of the range finding, and both the sensor and the pointer should be firmly fixed in place once it has been achieved so that it is continuously maintained.The turret will use the laser in the following manner. Once the target is detected through the image processing done by the tablet, the laser is pointed at the specified object. Then the image from the linear sensor is sent through the processor and wirelessly transmitter to the Android tablet. The tablet uses a programmed algorithm to look for the brightest pixels, which is where the laser is reflecting off the object. The location of this spot of light can be calculated by finding its distance from the edges of the frame.Next the system will go through the calculations to determine the depth of the target. The distance can be calculated from known geometrical formulas, as described previously in the Rangefinder section of Research. See Equation 2 and Figure for reference. The unknowns, then, are h, the vertical distance between the image sensor and the laser pointer, and θ, the angle. Equation 10 given below shows how to obtain θ from pfc, which is the number of pixels from the center of the focal plane, rpc, which is the radians per pixel pitch, and ro, which is the radian offset. Of these variables, only pfc is known, so it will be necessary to perform some calibration of the rangefinder derive the other two.Directory: seniordesign seniordesign -> Executive Summary 4 seniordesign -> Hvac control and Feedback System 0 Group 2 Steve Jones Mathew Arcuri Elroy Ashtian, Jr seniordesign -> Group 5 Spr-Sum 2011 seniordesign -> Senior Design II paper seniordesign -> Flight Performance Data Logging System seniordesign -> Amphibious vehicle seniordesign -> T-100 Watch Dog (Autonomous Security Vehicle) seniordesign -> Ehvac: Wireless Modular Multi-Zone hvac controller Group b javier Arias Ryan Kastovich Genaro Moore Michael Trampler seniordesign -> Table of Contents Executive Summary 2 Download 415.03 Kb. Share with your friends:
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