2.0 Discussion 2.1 System Overview In an effort to effectively and efficiently design and construct our system, we have divided the system into individual sections for construction and have identified the major components for the system. The primary components are listed below and Figure 2.1.1 displays the system diagram. - Current and voltage sensor - Transmitter and receiver pair - Data Storage - Micro controller - Pushbutton Keypad - Random Access Memory - PC Software - Liquid Crystal Display (LCD) User Appliance Outlet Sensors User s Receptacle Transformer Transmitter Receiver Figure 2.1.1 System Diagram Control Receptacle [1] Data Microcontroller Display Keypad PC In general, the user s appliance/device is plugged into a [provided] receptacle that has the remote components (e.g., sensors, transformer and transmitter) attached to its backside framing as to not be seen when the receptacle is inserted within the wall. The current/voltage sensors transmit the connected appliance s current and voltage usage to the step-down transformer, which decreases the monitored current and voltage variables to a manageable value, safe for the system s operation and manipulation. After leaving the transformer, the electrical values are transmitted via wireless telemetry through a transmitter using a predefined frequency. A receiver captures the data and routes it to a microprocessor for further manipulation. The microprocessor then determines when to route the information to be stored on the local storage drive, as well as when the data should be stored in the system s RAM. When one of the buttons on the numbered keypad is depressed, the display will emit a mild green light and requests the user to select P, V, or I for power, voltage, and current, respectively. The user then selects the corresponding button 1
for the desired electrical variable (i.e., button 1 for P, button 2 for V and button 3 for I ). Illustrations for both the keypad and the LCD are shown in Figure 2.2.9 and Figure 2.2.10, respectively. At the user s discretion, the storage card in the local storage drive can be removed and inserted into a floppy disk adapter for interfacing with the user s PC and system PC software. In the absence of the storage card, the microprocessor automatically routes the retrieved data to the system s RAM for temporary storage up to a pre-defined time period, at which point the system no longer stores data until a storage card (the original card or a new card) is inserted into the local drive. When the storage card is reinserted, the microprocessor automatically retrieves the data from the system s RAM and store in on the storage card. Each of the major system components and their respective function is described for further detail below. 2.2 System Components 2.2.1 Current and Voltage Sensors The current and voltage signals are detected through the use of a sensor. This sensor intercepts these variables and routes them to the transformer, which decreases the variables to a value acceptable by the entire system. Presently, Smith Research & Technology (SRT) has identified as the manufacturer for this component. Pictures of both the current and voltage sensors are shown below in Figure 2.2.1 and Figure 2.2.2, respectively. Figure 2.2.1 SRT Current Sensor [2] [http://www.srt-inc.com/dcappnote.html] Figure 2.2.2 SRT Voltage Sensor [3] [http://www.srt-inc.com/dcappnote.html] 2.2.2 Transformer The transformer is required to adjust the 120 V primary voltage produced by the residential electrical supply, to 5 V, which is manipulated by the system components. The transformer is concentrically wound, which reduces size. It also has a split bobbin winding and a low capacitive coupling design that eliminates the need for electrostatic shielding requirements and high costs. Stancor has been selected as the manufacturer for this specific component, and the model LB-610 has an input voltage of 115/230 VAC, an output voltage of 5 V, an input current rating of 20 A (providing the 15 A rating required for the system), and a current output of 110 ma. A picture of the LB-610 model transformer is shown below in Figure 2.2.3. 2
Figure 2.2.3 Stancor LB-610 Transformer [4] [http://www.hammondmfg.com/229.htm] 2.2.3 Wireless Communication The communication module provides the wireless link between the user s duplex receptacle and the control panel. The components to accomplish the communication are the transmitter and receiver. The transmitter is placed within the user s receptacle to obtain the data from the transformer. Through the use of a voltage regulator to adjust the peak-to-peak voltage values (eliminating the negative values), the transmitter transmits the data to the system s receiver. The Model TX-49 transmitter and Model RX-49 receiver, manufactured by Intelligent Wireless Systems, has been selected to provide data transmission capabilities for our system. Both the transmitter and receiver require a 5 V power supply provided by the residential electric supply; a step down transformer is used to decrease the 120 V residential power supply to 5 V needed to power the control panel. The components specifications as well as illustration are shown below in Table 2.2.1 and Figure 2.2.4, respectively. Table 2.2.1 iwireless Transmitter/Receiver Specifications [1] TX-49 RX-49 Carrier frequency = 49.878 MHz Signal bandwidth = 6 db / 20 KHz Range = 750 m / 2460 ft Antenna and transmitter dependant Bit Rate = 9.6 kbps Bit Rate = 9.6 kbps 43.2 mm x 31.8mm x 6.4 mm 48.3 mm x 36.8 mm x 6.4 mm. Figure 2.2.4 iwireless Transmitter/Receiver [5] [http://www.iwireless.com/html/txrx49.html] As can be seen from the Table 2.2.2 and Figure 2.2.2, the components are very small. This miniscule size makes the components simple to incorporate within the system s design. It was this characteristic that lead us to selecting this device. 3
2.2.4 Microcontroller The entire system is regulated through the use of a microcontroller. This device communicates with each component of the design and relays instructions based on its programming and architecture. It is also responsible for converting the data received by the receiver from an analog to digital signal through an internal Analog-to-Digital Converter (ADC). In an effort to obtain the correct values for the power, the microcontroller also calculates the power from the current and voltage data values obtained through the receiver. The microcontroller also initiates the storage process for both the storage drive and the RAM. When this storage function is performed, the microcontroller stores the information obtained from the receiver on the designated storage device along with a time and date stamp for variable versus time plotting capability through the PC software. The Model PIC16C765, manufactured by Microchip Technology, has been selected to provide processing capabilities for our system. This device has been selected due to its high performance central processing unit (CPU), low cost, and user programmable capabilities. The specifications for this device as well as an illustration are provided below in Table 2.2.3 and Figure 2.2.5, respectively. Table 2.2.2 Microchip Technology PIC16C765 Microcontroller Specifications [2] Key Features Program Memory Data Memory (bytes) PIC16C765 8 KB 256 Dual Port RAM 64 I/O Ports Analog-to-Digital Converter Module Parallel Slave Port Serial Communication Operating frequency Operating Voltage (Volt) 33 Ports 8 channels x 8 bit Yes USB, USART/SCI 6 MHz or 24 MHz 4.35 5.25 4
Figure 2.2.5 Microchip Technology PIC16C765 Microcontroller [6] [http://www.microchip.com/] This device has a built in analog-to-digital converter (ADC), which converts the data from the receiver to a digital value to be read on the display. 2.2.5 Data Storage The transmitted data is stored through a flash media storage drive, built into the control panel, onto a flash media storage card. For this storage card, SanDisk has been selected as the manufacturer and SmartMedia TM has been selected as the model. A picture of the storage card is shown below in Figure 2.2.6. Figure 2.2.6 SanDisk SmartMedia Flash Card [7] [http://www.sandisk.com/consumer/sm_card.asp] The flash storage card s dimensions are 35 mm x 35 mm x 2 mm, and it is capable of storing up to 32 MB of data. Data retrieved by the receiver along with a date and time stamp, is stored on the storage card (via the microprocessor) at a rate of 3 Hz or 3 times per second. This allows for accuracy despite on and off cycle times by the user s appliance. When the user s device is off, no data is stored. Therefore, only when the device is in operation is the data and time stamp be stored. The missing data points between the stored data points with a date and time stamp are assigned a value of zero by the system PC software. This maximizes storage efficiency of the flash card, which we have presently calculated to last six months. The card can be removed from the card drive and inserted into a Flash card adapter for access through the PC software. The flash card adapter, shown in Figure 2.2.7, has the same size as a standard floppy disk. After the user has stored enough data, the user inserts the flash card into the flash card adapter. The user then transfers all the data onto her/his local PC for data analysis through the system s PC software. The driver required for the flash card adapter operation can be downloaded from the Internet for free of charge. As a courtesy, a storage card is provided to the user in a 32 MB format although various memory sizes are available with cost adjustment. The floppy disk adapter for the storage card is the FlashPath Adapter model, also manufactured by SanDisk. An illustration of the adapter is shown in Figure 2.2.7 below along with its specifications in Table 2.2.4. 5
Figure 2.2.7 SanDisk FlashPath Adapter [8] [http://www.sandisk.com/consumer/flashpath.asp] Table 2.2.3 SanDisk FlashPath Specifications [3] Host interface 3.5 floppy disk drive (1.44 MB) Dimension 90 mm x 94 mm x 3.3 mm Smart Media 2 MB 128 MB Memory 8 MB or more Package Included Floppy disk adapter Button type battery: CR2016 (2EA) FlashPath setup disk Floppy Disk 3.5 floppy disk drive supporting 1.44 MB The storage drive for the storage card is a standard PCMCIA flash card reader. Primary Solutions has been selected as the manufacturer for this device. Table 2.2.5 lists the features of this device and Figure 2.2.8 provides an illustration. Table 2.2.4 Primary Solutions PCMCIA Card Drive Specifications [4] - Complies with PCI Local Bus Specification - Supports all kinds of PC Card HOT- 2.1 SWAPPING feature (except Win NT) - Complies with PCMCIA PC Card 95 / - Supports Type I, Type II, Type III PC CardBus standard specification card sockets - Active LED indication of busy - 1 year warranty - Supports ATA Flash Card, CF Card + CF - No need for any ISA IRQ Board Adapter, SM + SM Adapter, IBM Microdrive, type III Hard Drive, IOMEGA Click! Card, Sony Memory Stick +Stick Adapter, Linear Flash Cards (AMD, Intel II & II+, etc. chipsets), SRAM Card, Fax Modem Card, LAN Card, Wireless LAN card, I/O card, Cardbus card, etc 6
Figure 2.2.8 Primary Solutions PCMCIA Card Drive [9] [http://www.psism.com/pci_rear_reader.htm#202e] 2.2.6 Random Access Memory (RAM) 512 KB of RAM (two 256 KB RAM chips) is required to temporarily store data in the event the storage card is removed. This system audibly notifies the user with three short beeps and displays a red light emitting diode (LED) on the front of the control panel to alert the user that the system is in Self-Storage Mode, and the data received from the microcontroller is being stored on the system s RAM (for up to 1.5 hours). This provides up to 16,200 data values for the current and voltage (stored at a frequency of 3 Hz). The system also performs this same alert procedure when the flash card has reached 95% of its capacity, after approximately six months of operation. This requires that the storage card be cleared through the system s Clear feature on the control panel, or the storage card be replaced. The RAM is standard synchronous dynamic random access memory (SDRAM). 2.2.7 Pushbutton Keypad The numbered keypad is required to operate the display of the control panel and to select the desired receptacle (one duplex receptacle device is provide, however others can be added on through eight expansion ports in the control panel). The pushbuttons also control the backlight feature, which is discussed in the following section for the LCD. SwitchesPlus has been selected for the vendor for this device. It has dimensions of 1.10 x 2.19 x 0.21 in. It is made completely out of aluminum, which makes it durable. The port at the bottom of the keypad connects directly to the microprocessor for interfacing. Figure 2.2.9 displays this device. Figure 2.2.9 SwitchesPlus Pushbutton Keypad [10] [http://www.switchesplus.com] 2.2.8 LCD The display is a 16 character by two-line display that shows the current time and date when none of the pushbuttons are selected. When a pushbutton is depressed, the display emits a mild orange-red glow and Select an outlet is displayed. The user is then required to select 1-8 according to the number of user receptacles. Once this selection has been made, the display shows Select P, V or I. The user then is required to select 1, 2 or 3 (Power, Voltage, and Current, respectively). The display then shows the current data value in the microcontroller based on the number selected. Optrex has been selected as the manufacturer for this component. Its low cost and the quality were the governing factors in selecting this model. An illustration of the device is shown in Figure 2.2.10. 7
Figure 2.2.10 Optrex 2 line x 16 character LCD [11] [http:// www.optrex.com] 2.2.9 Software The microcontroller writes the gathered current, voltage, and power values to the storage card through the storage drive. This data is stored in format recognized by the PC software, which has a file extension of.piv. When the floppy adapter (with inserted floppy card) is inserted and the software program invoked, the software asks the user for the location of the.piv file. Once the user directs the software to the correct location, the software accesses the.piv file on the storage card. It then allows the user to generate plots of each electrical variable versus time, as well as provide total power consumption over a user-defined time period. An outside contractor is presently being researched for the software s development. 4.0 Cost and Time 4.1 Fiscal The costs associated with our design are shown below in Table 4.1. Table 4.1 Component Cost [5] Component Cost Sensor (current/voltage) $13.50/$20.00 Transformer $10 Transmitter/Receiver Pair $86 Microcontroller $10 512 MB RAM (256 MB x 2) $170 Storage Components $100 16 x 2 Liquid Crystal Display (LCD) $23 Twelve Pushbutton keypad $25 Software $200 Total Component Cost $658 Manpower (55 hrs @ $60/hr) $3300 Installation Included Grand Total $3,958 As can be seen from the table, the largest components are the RAM, the storage components, the software component, and the manpower. The RAM is standard SDRAM, and thus, the average cost for one 256 KB RAM chip is approximately $85. The cost for the storage components includes the storage card, storage card reader, and the floppy disk adapter. The software will be contracted out and thus, its cost accounts for the expense associated with outside contracting. Presently, the total component cost is $658.00. However, 8
$200.00 accounts for the one-time contracting fee for the software. Thus, the long-term component cost will be approximately $458.00. 4.2 Time For this design, a total of 55 hours are required for completion. This estimation includes 25 hours of research, 20 hours for the design, 5 hours installation, and 5 hours for the supplies. A detailed timeline for design implementation is show in Figure 4.1. Evaluation of RFP and Project Preliminary Design Specifications Design Layout and Specifics Request for Information Delivered Component Research and Data Collection Cost Analysis Preliminary Proposal Delivered and Presentation Given Progress Report Delivered Final Design Overview Draft Final Proposal Delivered Final Proposal Delivered and Presentation Given April 1st April 15th Figure 4.1 Timeline Chart [12] May 1st May 15th 9