Table of Contents Executive Summary 2
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- 2.6.1 PCB Selection
- 2.6.2 Microcontroller Selection
- 2.6.2.1 Development Tools
- 2.6.3 Display Selection
- 2.6.4 Wireless Selection
- 2.6.5 Pushbutton Selection
- 2.6.6 Battery Selection
- 2.6.7 Case Selection
- 2.6.7 Surface Mounting
2.7 Umpire IndicatorUsing the basic functions of a current umpire indicator 2.6 Figure 1 shows an example of a currently used umpire indicator. To digitize this device push buttons are to be used instead of moving wheels to advance the multiple variables. To still allow the user to preview the values of the balls, strikes, and outs small LED or LCD screens are to be used to display the numbers. Then to complete a goal of this project to send the data of this indicator to the database wireless communications need to be included in this device. For any of this technology to work a microcontroller will be needed to direct and control all the various functions of this device.  
2.6 Figure 1: Analog Umpire Indicator – printed from Marwort Sporting Goods Company – Permission Requested 2.6.1 PCB SelectionDue to the requirements of this project, the umpire indicator will need to be place on a printed circuit board (PCB). The fairly simple requirements of the umpire indicator component wise allows for two main methods of acquiring the appropriate PCB for our designs. The small size and low component count of the design of this project allow the creation of the PCB to be done by the group to be an option. The necessary equipment and knowhow for constructing the PCBs is easily available via the Internet and hobbyist shops locally in Orlando. When researching the processes and requirements to creating the PCBs needed for this project, the group was pleasantly surprised at the common household appliances that are needed to make homemade PCBs. The necessary supplies for making PCBs are glossy magazine pages, a laser printer, a clothes iron, scrubbing pads, nail polish remover, clothes hanger, copper clad laminate and etching solution. Of these necessary supplies the only needed to be purchased are the copper clad laminate and the etching solution. Both of these supplies are easily available from RadioShack for $3.99 for a 4.5” x 6” piece of two-sided laminate and $9.99 for a 16Oz. bottle of etching solution. The process of designing the PCB is relatively easy using software like the free software from ExpressPCB or Cadsoft. Upon designing the proper PCB layout the design can be printed on the glossy magazine paper in mirror layout. The image then needs to be ironed onto the copper clad laminate. After the laminate has properly cooled the paper can be dissolved in water and the ink from the laser printer will still be on the copper laminate. The laminate is then placed into the etching solution for around 10 minutes. After this has been completed the ink is still on the laminate and the copper has all been removed. Nail polish remover easily removes the ink leaving very nice traces for the components of our design. At this point the next step is to carefully drill holes for the though hole components. That leaves a completed PCB made by the group for the senior design project. The benefits of this process is that the creation of the PCB can be done in under one day and any issues with faulty design can be easily and cost effectively fixed by altering the current PCB or creating another PCB following the same process. The drawbacks to this process of the group making the PCB is that the designs of the PCBs must be on the simpler side of designs capable with manufacturers such as Express PCB. Also the chances of defects due to not properly completing the processes described above could completely destroy a PCB. Several trial runs will be needed to master the process of the group making the PCBs but having to create multiple PCBs will still be markedly more cost efficient at $3.99 per board than having the boards manufactured. The second method to selecting how to get the necessary PCB for the design is by choosing to go with a manufactured PCB. The PCB manufacturers looked at for this project are ExpressPCB, 4PCB and PCB123. ExpressPCB and 4PCB both have student pricing which will be utilized if the PCB is chosen to be purchased from a manufacturer. The main options from these two providers are that there is a two-layer variety and a four-layer version available for purchase. The benefit of the 4 layer version is that the power and ground layers can be whole planes inside the PCB. This allows the PCB to be smaller and have a reduced number of traces on the top and bottom of the PCB. Having the PCB be 4 layers is also almost double the price of a standard two-layer board. For the purposes of this design a four-layer PCB is an unneeded expense and will not be used. Using a manufactured board has many benefits that cannot be achieved when the group makes the board. When choosing to go with a manufactured board the resolution of the lines can be as fine as 0.006” in width and 0.006” spacing between etchings. These are resolutions that cannot be achieved with the group creating the PCB. The next thing to consider is pricing deals of the two available PCB manufacturers. ExpressPCB has a $51 deal were three identical 3.8” x 2.5” PCB can be purchased to use in the design. The price of these three identical boards is very economical but the design made by the group has no need other than for backup purposes for a secondary board. 4PCB also has economical prices for manufactured boards. 4PCB offers up to 60 square inches of PCB area for $33. This is an approximately 8” x 7” piece of PCB material. This is substantially larger than the PCB needed in the handheld device but the benefits of a cheaper option with no wasted budget in identical boards is worthy of consideration. 4PCB also allows student buyers to purchase only a single board at a time to aid in cost effectiveness. The convenience of buying a manufactured PCB versus the group making one is that the schematic designs from the free software from that manufacturer or the Eagle Light software can be submitted in an email to the manufacturer and the PCB can be made directly from that schematic. This maximizes the exactness of the PCB design with almost no possibilities of manufacturing defects. Also there are benefits of having a manufactured PCB that aid in the assembly of the circuit. If the group chooses to have the PCB manufactured for the purposes of this project the PCB will be silkscreened and the component holes will be properly marked for direction and polarity of the parts. This allows for a speedier assembly of the PCB and less mistakes with backwards components. Purchasing a PCB will definitely be considered when assembling the design. The benefits of very high accuracy in the traces and component holes and surface mounts and also the advantages to having a fully labeled PCB outweigh the cons of having to wait up to ten business days for the manufactured PCB to arrive and the possibility of having to have a new PCB made and sent out. 2.6.2 Microcontroller SelectionOn the market today there are near countless varieties of microcontrollers from large high current high pin count designs to small very low power consumption microcontrollers. For this design the group needs a design that is in between these two extremes. The group needs a microcontroller that will easily connect to a basic transmitter to send the data. The microcontroller will also need to hook up to at minimum three LED displays that have eight unique pins apiece and one pin in common with each other or twenty-five pins total for the analog LED pins. There will also need to be three or four pins for the push buttons. This means that a 32 pin I/O microcontroller should be able to fully complete the necessary requirements for this project with these pins being either analog or digital configurable. Another step in researching for microcontrollers is choosing a chip that codes in a language that is understandable and much less complicated overall. C programming is the language that the group desires to be coding in, it is much simpler to code in, debug in and explain the happenings of to people following the project. C programming also aids the group in having easily implementable functions that work in the design of this project because the umpire indicator needs to stay in a process of looping and waiting. C programming has a very simple looping scheme with several different types of loops. Also since the device has several displays in use, these displays will need continually updated information. This can be easily accomplished by doing a print in C programming. The Arduino Pro Mini is an investigated microcontroller. Having a free programmer for the Mini simplifies design procedures and can be downloaded to use with the microcontroller. This chip certainly has the abilities for data transmission needed in this project. Another benefit of this microcontroller is the very small footprint it would take up in the confined space of the umpire indicator at just 0.7” by 1.3”. The specifications of this chipset are shown in 2.6.2 Table 1 of this document. The major drawback of this design is the limited number of I/O pins of only 14 available on this chipset. With the displays requiring numerous numbers of pins apiece this chip really cannot be used for the needs of this project.
2.6.2 Table 1: Specifications of Arduino Mini Pro The last investigated microcontroller for this project was the PIC24HJ64GP204 from microchip.com. This microcontroller showed many of the same benefits as the Arduino board with significantly more pins to connect to the numerous pins required of the 7-segment displays. The PIC24 microcontroller benefits from a c complier optimized instruction set for ease of programming and has up to 5V stable digital output pins for triggering the display drivers to display the appropriate data whatever the triggering voltage might be. This chipset also benefits from sleep functions or low power states to aid in better battery life of the handheld device. The onboard clock is beneficial for looping procedures and keeping track of when to update the information in the registers for faulty input rejection. This microcontroller is also economical at $5.10 from the microchip.com website. 2.6.2 Table 2 shows an abbreviated table of specifications that make the PIC24 microcontroller a good choice for this project.
2.6.2 Table 2: Specifications of PIC24HJ64GP204 2.6.2.1 Development ToolsOne of the easiest ways to program the microcontroller chosen for this project is through the use of development tools. These tools can also later on in the testing phases of this project be used for evaluating whether the code is correct for the device and to see if the appropriate peripheral components are getting the appropriate information. One of the things that make development tools so convenient is their ability to connect with the computer so that code can be transferred to and from the development tools and the microcontroller itself to debug the chipset and implement any test programs available from outside sources like the Internet. The development tool for the PIC24H family of microcontrollers is called the Explorer 16. The Explorer 16 has a great number of useful features. The Explorer 16 has a very large onboard screen useful for displaying outputs and data that would be sent to a peripheral screen, but also is useful for displaying debugging information while in the testing and programming phase of implementing the microcontroller. This development tool connects directly to all MPLAB software supplied by Microchip and also has the ability to hook to a computer via USB or RS-232 serial ports. Another unique feature is the ability for the Explorer 16 to very accurately measure the heat being dissipated by the microcontroller to rapidly warn the user of over-current happening in the device. The Explorer 16 also comes with a large amount of software including an MPLAB C compiler that allows C code to be put on the chip through the controller. The largest drawback to the Explorer 16 is the cost of the device. The Explorer 16 is $339 from the microchip website. 2.6.2.1 Figure 1 shows the Explorer 16 and all included items that come bundled with its purchase. 
2.6.2.1 Figure 1: Explorer 16 Development Kit – printed from Microchip.com – Permission Requested 2.6.3 Display SelectionWhile researching, two main designs for displaying the information of the handheld umpire device were investigated. The first design looked at for this project was the LCD display. LCD displays are very powerful display devices, with the ability to display fairly large amounts of information at one time on the display. A good example of this design is the Hitachi 44780 based module. This module has the ability to display up to 2x20 characters of information, which would consist of ball, strike, out, and inning counts and possibly even battery life of the device. The amount of information that can be displayed to the user is great but the coding and pin configuration of this display can be unruly and time consuming. The 44780-display controller requires 12 pins of a microcontroller to work properly. This in itself is not a very big issue, but the coding of the LCD’s microcontroller has the potential to be quite difficult to display information that is completely understandable if just displayed as a number. Another issue with using this device is its actual size. Although the controller is not all that large, choosing a screen that is roughly 1.5” x 2” and putting it on a hand device that is roughly 3” wide by 5” tall would be deemed overkill. The second investigated screen design is to go with individual 7-segment LED displays. These individual LED displays will have laser engravings above the general locations of the current design of the umpire device. These LED segments need to be no larger than half of an inch tall as that is still substantially larger than the existing numbers. Each of the displays has a ten-pin configuration with only 8 unique pins but the decimal point will not be used for any of these numbers. This makes the needed pin count per 7-segment display go to a count of seven pins and a total number of pins for all three displays of 22 pins. These pins need to be analog pins with a forward voltage of 2.6V to turn on the individual display segments. Some of the unique features of the LCD display are lost with this design however. The ability to display user messages and more information than just the numbers of balls, strikes, and outs is now lost. Also the battery can no longer be displayed on the screen. These are all acceptable losses because changing to 7-segment displays from a LCD design maintains a higher level of commonness between the existing umpire indicator and the one the group is designing. This aids in shortening learning curves of learning the equipment, which is a goal of this project. To keep the ability to monitor battery life a dual function LED battery life/power on indicator will be used. This LED for example will turn on green to indicate that the device is on and perhaps turn red to indicate that the 9V battery has reached a standard threshold of low battery. The LED 7-segment displays were found at webtronics.com for $0.48 per screen. Another option to controlling the 7-segment displays is to use a controller for them like the 4511ic found at hobbyengineering.com for $0.99 per chip. This integrated circuit is a BCD to seven-segment display decoder. This device allows for a ten pin LED alphanumeric display to be controlled by only four pins of the microcontroller. This greatly simplifies the required coding of the microcontroller and the number of pins needed on that microcontroller. Another benefit of the 4511 is that it has inputs of a CMOS design. These inputs allow for a very low amperage input to be applied and still have the 4511 see that the input has been triggered. Most microcontrollers have the ability to supply fairly high voltages to the I/O pins, upwards of 5V, but seldom can supply amperages enough to turn on an LED. With the very high sensitivity to signal that the CMOS technology brings to the 4511 it is possible to directly connect the microcontroller to the 4511. By implementing the 4511ic the number of pins for the 7-segment displays is reduced from 22 pins to operate the displays with analog pins to needing only 12 pins to operate the three displays with the pins being able to be digital pins. Since the microcontroller that the group is looking at using for this project has mainly digital output pins this is the best solution to using the LED displays. 2.6.4 Wireless SelectionThe available types of wireless technology on the market today make it almost daunting to select a specific type of wireless technology. The numbers of technologies investigated from simple RF transmitters to Bluetooth to Wi-Fi technologies were numerous. To start the search for the correct wireless communication device the group looked devices compatible with using Wi-Fi. A benefit to having a Wi-Fi based chipset is that all of the technology from the umpire indicator to the coach tablets can all be on the same wireless network and this greatly improves the speed at which the data can be stored and recalled between the necessary parties. When investigating these devices the group discovered very few chipsets that were even able to connect to an existing Wi-Fi environment. The issue seems to be that the necessary protocols of Wi-Fi are more extensive then are wanted and needed in the chipsets the group wants to investigate for this project. Another investigated area of wireless communication is RF transceivers. The ranges of available chipset are very large in the RF transceiver category. One of the chips researched in this category was the XBee 802.15.4. This XBee wireless module would certainly achieve the necessary amount of data throughput at the chips operating 250kbps. The XBee is also reasonably affordable at $23 from Digi-key. Another benefit of the XBee is that it has an operating voltage of 2.8V – 3.4V that works well with the microcontrollers 3.3V. Some of the drawbacks to the XBee chip are properly coding the output from the microcontroller to work with this chipset and having an appropriate receiver if not a matching pair of transceivers to transmit the data. The information recorded on the handheld device is not all that involved or requiring of very high refresh rates, however, and very advanced wireless systems are not needed. This greatly reduces the need for sophisticated transceiver based designs. All this project requires is a simple transmitter only RF design as apposed to a 2-way design that operates at a slower frequency but increased range is a good idea with this project because the data to be sent is a simple sequence of push button readings. Having this simplification of the design the group searched for a wireless RF chip that was a transmitter and receiver pair to make a wireless system that properly sent the one-way data over a distance that exceeded adequately the approximate 200ft range from the umpire to the scoring box. The 2KM Long Range RF transmitter pair that is being investigated for this project has many features that make it work very well for the design and was found at SeedStudio.com for $18.00. The RF Link has an operating voltage of 5V that is easily achieved with the power supply the group will be designing. Another feature that is beneficial for the purposes of this project is that the operating range of this specific transmitter receiver pair is up to 2000ft. This is quite a lot over the needed amount of range but there are many factors that have a potential to shorten range. The Umpire Indicator being a handheld device has the potential of having a reduced range because it is in the umpire’s hand. Another factor that has a potential of reducing range is the batteries running low and full voltage not being supplied to the wireless chipset. This chipset also has other benefits. The transmitter is designed to send data from a four-port system individually to the receiver to be used to input into the database system. This is very beneficial because there is a maximum of four push buttons that will need to be monitored for this system. 2.6.3 Figure 1 is the image of the RF link. There are a few drawbacks to this design approach however. The transmitter is installed internally in the device while the receiver needs to have a secondary device made for it to function with a computer via USB or a serial port or the coaching tablets. This is an added step that requires a computer to be used with this design that might not be necessary. Further options need to be investigated to see if making a receiver dongle using the 2KM RF pair is the best option.  
2.6.3 Figure 3: Long Range RF Link – printed form SeedStudio.com – Permission Requested The last investigated method of wireless communication is Bluetooth. There are many features of Bluetooth that cannot be overlooked for this design. Bluetooth is being implemented into many new devices as a standard feature and is available in the tablets that will be used by the coaches in this project. Connecting to a device over Bluetooth simplifies the design such that the receiver for the 2KM would not need to be built and eliminates the need to use a USB dongle in one of the tablets or have a secondary computer at the field for the RF transmitter to talk to. This from the very beginning of investigating Bluetooth lends us to choosing it as the method for transmitting the umpire indicator data in this project. The Bluetooth chipset the group is investigating for this project is the LinkMatik 2.0 found at mouser electronics for $50.89. This is one of the most expensive options of the several investigated but the group feels the benefits of using this chipset out way the expense. This Bluetooth device has plenty of distance at a range of up to 100 meters and is conveniently powered by 3.3V. The transfer rate of this chipset also completely meets and exceeds the desired results of this project at a default setting of 9600 Baud. The thing that most interests the group to use the LinkMatik chipset over the other options is the LinkMatik’s ability to connect to more than one Bluetooth device at a time. The LinkMatik can actually connect to up to four devices at the same time to send the data to the pair of coaching tablets. Another benefit of this chip is the built in sleep function where power consumption drops from ~25mA while transmitting to ~370uA while sleeping. 2.6.4 Figure 2 is an image of the LinkMatik Bluetooth transceiver and its dimensions are 35.5mm x 14mm x 2.3mm. 
2.6.3 Figure 4: LinkMatik 2.0 – printed form flexipanel.com 2.6.5 Pushbutton SelectionThere is a minimum of five buttons on the umpire indicator the group is designing for this project. The selection of buttons on the market that can fill the needs of what the group requires for this project are numerous. To narrow the available buttons to choose from the group eliminated unneeded features. Lit buttons are not needed for the requirements of this project, nor are buttons that are very large or colored. The way that buttons trigger is also very wide ranging. While searching for the proper buttons for this project the group found buttons that were on in their resting state then off when they were pressed, buttons that when pressed clicked on and then required a second press to click off. These are not the types of buttons the group is looking for. Research was done into momentary trigger buttons that only when pressed read an on setting and then go back to an off or low setting when no longer pressed. Choosing these specific wants narrowed the available buttons considerably and the group was able to find a five pack of buttons with a small footprint from pololu.com for $0.95. This button can withstand a voltage of up to 12V, which is over the maximum voltage used in this project of 3.3V and can withstand up to 50mA of current flowing through them. Since the group is just using these buttons as interrupts and not power buttons the design should never even get close to 50mA of current through the pushbuttons. The dimensions of this mini pushbutton are shown in the image of the switch seen in 2.6.5 Figure 1. 
2.6.4 Figure 1: Mini pushbutton dimensions – printed form pololu.com 2.6.6 Battery SelectionAt this point in the research of this project most if not all of the components needed to beginning designing the umpire indicator have been found. This makes what to power these components with the next item to be investigated. Knowing that the designed device is handheld and has to be as portable as possible batteries for the device is the only option. There are many types of batteries on the market today that would prove useful for the design of this project. The two main categories of batteries available today are standard disposable batteries or those that have the ability to be recharged. Both of these types of batteries show promise for this project. The disposable battery type is very easily found and easily replaced; there is no need to worry with recharging and no issues with not being compatible with the device because of very standardized sizes of batteries available. The rechargeable batteries need to be properly investigated for this project because of the cost saving benefits of the user not having to spend money on repeat purchases of batteries for the umpire device. There are five main chemical varieties of rechargeable batteries on the market today: Alkaline, Lead-acid, Lithium-ion, Nickel-cadmium, Nickel-metal-hydride. Alkaline batteries are most likely the lowest cost batteries of the group and are widely available and commonly used in consumer electronics of wide variety. The Alkaline has a number of benefits that would prove well for this project. The inexpensive nature of this battery is one of the biggest advantages of this battery. The alkaline batteries also have a very low self-discharge and can be shelved for long periods of time and still maintain most of their charge. Another advantage to the alkaline rechargeable battery is that the chemical makeup of this battery uses non-toxic metals. The disadvantages to this battery though are that the batteries life reduces with every cycle of its charge and only holds 60% of the manufacture’s claims of current hours after only a few charges. Another drawback to this battery is to prevent shortened life this battery needs to be charged before the battery gets too low. The next investigated type of battery is the lead-acid battery. The lead-acid batteries are also a very common battery but do not show many promising properties that would benefit the groups designed umpire indicator. Lead-acid batteries are heavy and offer a low weight to charge value. Also charging of these batteries is often very slow. Also the small amount of current draw of umpire indicator is not ideal for the large current able to be supplied by the lead-acid batteries. Another drawback to the lead-acid batteries is that the materials that make up this battery are harmful for the environment. Special care needs to be taken to dispose of these batteries properly. Lithium-ion batteries are a very new technology but are becoming very widespread in electronic devices like laptops and cell phones. Lithium-ion batteries show promise for use in this project. Lithium-ion batteries have a very good weight to charge ratio and do not have to be periodically discharged and have no memory. Some of the disadvantages to using lithium-ion batteries are a poor shelf life and discharging the lithium-ion cell below the defined low voltage point of the cell can completely render the battery useless. These batteries are available in some standard sized batteries but more often are custom made for the device they are installed in. Because of the need to minimize budget and the short time that the group has to construct this design, having a battery made for the umpire indicator is not the best option. Nickel-cadmium batteries are one of the oldest varieties of rechargeable batteries. These batteries offer a large number of cycles for recharge compared to the other battery choices available today and charge faster than most of the other types of batteries investigated. Some of the disadvantages of this battery are a low power to density rating when compared to the other batteries in the rechargeable category. The nickel-cadmium batteries also have a memory and need to be periodically fully discharged and recharged again. Another disadvantage is that the nickel-cadmium batteries have a fairly high load capacity but do not respond well to the mild load over a prolonged period time like the design of the umpire indicator. Because of the umpire indicator not being well suited for this type of battery nickel-cadmium batteries will not be used with this design. The last rechargeable battery type to be investigated for this design is the Nickel-metal-hydride battery (NimH). NimH batteries are growing in popularity in the market and are going to be considered for use in this design. NimH batteries have a higher capacity than the nickel-cadmium batteries and are also less prone to memory losses. Another large advantage to this type of battery is that it is an environmentally friendly battery that has only mildly toxic materials used in its construction. Some of the disadvantages of this battery type is that it needs to be fully charged every few months to avoid deterioration of the charge material inside the battery. Also the NimH batteries have a fairly high self-discharge rate. Even with these limitations Alkaline and Nickel-metal-hydride batteries will be investigated for use as the battery source for the umpire indicator designed in this senior design project. 2.6.7 Case SelectionThere are many things to consider when choosing what to encase the umpire device in. What the case is made out of is important to consider. Also the size of the enclosure is very important because this defines whether or not the umpire indicator the group is designing is still able to be handheld and if it has maintained the usability of the traditional device. If the group uses the traditional umpire device as an example of what to choose for the case material the choices consist of various types of plastic and metals such as aluminum and stainless steel. These are very good options as to what to encase the designed umpire indicator in. The first option is stainless steel. Stainless steel cases definitely have an appearance that stands out as being a unique item. In fact nearly all of the cases found near the size requirements of this project were predefined for a specific purpose. There were many cases found made of stainless steel found for portable mp3 players and even some varieties of cell phones. Other cases that were found out of this material were found to be niche items such as cigar cases and the like. Because of the specialization in all of the cases found out of this material none were deemed generic enough to use for the purposes of this project. The next material investigated as a case for this project was those constructed out of aluminum. Aluminum is a soft enough metal to be easy to drill and light enough as a metal to be able to use as a handheld device case without fatiguing the user because of the weight of the case. The best examples of aluminum cases are those that have been extruded. Extruded cases are well known in the circle of prototypers and hobbyists of small-scale electronics. Many of the extruded aluminum cases also have built in grooves to slide PCBs into the cases and have them stay securely. Of the cases found made out of aluminum one of the best suited for the needs of this project was the TEKAL22-B.29 from tekalenclosures.com. This black enclosure has the dimensions 5.708” x 3.378” x 1.453”. The internal grooves allow for this case to hold a PCB of up to 115.5mm x 80.5mm. This is quite a large PCB with ample area for the design of the umpire indicator to be implemented on. Another feature of this design is that the case comes with the ability to hold either two AA batteries or a single 9V battery. This feature could come in very handy, as one of the options to power our device is a single 9V battery. From the tekalenclouseres.com website this extruded aluminum case would cost $21.18. The last case type to be investigated is those made of plastic. Plastic cases are very lightweight and easy to use. Because of the versatility of small plastic enclosures, there are a large amount of them to choose from. Plastic cases are very brittle, however, and can be cracked easily while drilling the appropriate holes for the screens and pushbuttons. Knowing the approximate dimensions of the case that would be needed for this project the group narrowed the selection of cases down to those that met the needs of the case for the umpire device. Because this project will be battery powered a case with a changeable battery compartment would be useful. Another feature that the case needs to have is the ability to hold a PCB inside securely. Reducing the available selection of cases down to the ones that meet this criteria two were found that worked well. Both of the cases were found at allelectronics.com for approximately $5. The first plastic case investigated is part number 1593-QBK. This case can hold PCBs internally with an included battery compartment and has an external dimension of 2.6” x 4.4” x 1.1”. The second case from allelectronics.com has almost the same dimensions as the previous case but is slightly longer to accommodate the extra space taken up by the battery and has final dimensions of 2.6” x 5.45” x 1.1”. This case can enclose a PCB of up to 2.25” x 3.81”. From the cases looked into for this design there are two things to be decided to choose which case is better. If the necessary space for the PCB is that of the aluminum case and a cost of four times as much is not an issue then the aluminum case should be chosen. With the extruded aluminum case and the plastic case being almost the same size however and cost is an important factor for the group, the group is considering the plastic case from allelectronics.com as the enclosure for this project. 2.6.7 Surface MountingAfter completing the necessary research for this project, it has been found that some of the parts needed for this design are surface mount components. Surface mount components unlike through-hole components have all of the pins of the device closely grouped and the components sit closer to the PCB and allow for multi layer PCBs to be used because the mounting points do not disrupt the other layers of the board. There are several drawbacks however to surface mounted components. The very small nature of these components and the extensive amount of pins make soldering by hand very problematic. The microcontroller for example has 44 pins on the chip. These pins are all surface mounted pins and the whole chip is slightly larger than one inch squared. The exactness that must be used to surface mount these parts by hand are a skill that must be acquired or paid for. There are businesses in Orlando that are thoughtful to students in need of having their components surface mounted and will do so for these groups at a reasonable if not free of cost to the group. This is an option for the larger more delicate items of this project, but the group feels that both knowing how to surface mount parts and the time and cost saving benefits of not having to rely on a companies availability of doing the surface mounting are worth the time and effort it would take to as a group learn how to surface mount parts. The Internet is a very useful place to gain knowledge on how to surface mount parts. One member of the group or the entirety of the group will need to utilize the guides and videos available online to gain tips on how to best surface mount parts. There are a number of specialized tools needed to surface mount parts that need to be investigated in order for the group to successfully mount all of the parts. The first thing to be acquired is a regulated digitally controlled soldering iron. Electronic components are very sensitive to heat and only a short amount of time can be spent touching any given pin. When soldering chips that can have pins as small as .2mm or smaller a 10x loupe or microscope can be very helpful if not necessary. The solder used needs to be around 0.015” in diameter and a solder braid will be very useful to suck up any unwanted solder left from accidently bridging adjacent pins or being messy with the soldering process. The main thing that is needed to properly surface mount components is flux paste or some kind of flux pen. Flux is the agent that allows the solder to bond the two metals of the lead of the component and the metal substrate of the PCB. For the group to successfully be able to surface mount the necessary parts for this design, all of the supplies will need to be budgeted for and acquired. The next step to become proficient at surface mounting parts is to practice on less important parts of the design or on scrap parts to perfect the method and timing of steps to avoid destroying chips that are costly. The group will certainly use the beginning weeks of the building of the umpire device to perfect their soldering skills of both surface mounted parts and through hole parts so that the finished PCB is both fully functional and professional looking. Directory: seniordesign -> fa2010sp2011 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 -> Remote Touchscreen-Controlled Defense Turret Senior Design Documentation Courtney Mann, Brad Clymer, Szu-yu Huang Group 11 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 Download 471.88 Kb. Share with your friends:
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