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5. 750 Wolves Calculator Deconstruction

Team 750W - Wolves Texas Instruments Electronics Online Challenge By Shiven Kumar, Rahul Shah, Jasmine Parekh, Tejas Latupalli, and Suthikshan Karthik Link to Google Doc: https://docs.google.com/document/d/17zUo_AFhkpOZtJM2ojZOifho3UPX_Hp5DT9eyUyzGb8/edit?usp=sharing  Summary: Our brains are amazingly versatile, however we can often find it hard to calculate and compute numbers in our heads because they can store only so many numbers. According to a famous researcher in the 1950s, George Miller, we can only remember an average of 5 to 9 digits before our brains start to ache and fail to recall. That’s why people have been using aids to help them calculate from literally the beginning of time. From abacus to modern, more advanced colored graphing calculators, counting “machines” have been an incredibly useful piece of technology that many take for granted. We specifically chose to disassemble a Texas Instruments TI-84 Plus C SE because of how useful calculators are in our daily lives. In school, or even at home, to students in high school like us it is a piece of technology that is constantly used and depended upon. So, our team decided to take one apart to see how it works and what parts it is made of. First, we removed the battery door and the rechargeable battery, and then the back of the calculator. This exposed the main PCB of the calculator, giving us the ability to see the protective foil shield covering parts of the fragile circuit board. After removing this, we saw the CPU, memory, capacitors, and other electronic circuitry, wiring, and connectors. Then, we removed the front keypad of the calculator, showing us how each press of the plastic button compresses a rubber membrane, which then touches a golden - colored contact switch beneath each key. This allows the calculator to register which key has been pressed. We connected this type of technology to the mechanics of a desktop membrane keyboard as they both are quite similar, just different in scale. Taking a closer look at the PCB, the ribbon-cable connector from the circuit board to the LCD display is visible. This cable transmits the visual signals from the integrated graphics processing unit, or GPU, on the main CPU to the screen, allowing calculations, graphs, and more to be seen. The CPU of this calculator is actually made by Texas Instruments - a model T6TX7AFG-0002 according to the number inscribed on the silicon. The way that this calculator works is very similar to the parts of a computer, only on a smaller and less powerful scale. Both have RAM, a CPU, GPU, and other very similar parts. The top of the PCB has two connectors - one miniUSB, and one round power plug. The miniUSB connects directly to the battery, for charging, while the round power input provides power from a wall outlet for continuous usage. The bottom of the PCB also has two contact points, which were linked to two metal contacts on the outside of the shell. These contacts are also connected to the battery charging circuits, for use with a dock rather than a cable. By removing the polarizing filters from the disconnected LCD, we found out that the screen was likely a TN panel, similar to some older flat screen monitors. This means that the panel can refresh quickly, but does not have as vibrant colors or wide viewing angles like the IPS displays used in most new laptops, phones, and TVs. The polarizing filters help direct the light, and make sure that the backlight spreads evenly across the liquid crystal in the display. Finally, we grouped all the parts together, seeing how tightly they fit into the relatively compact frame. This really amazed us, as only a few decades ago, computers took up entire rooms, and now a powerful calculator can fit into a small, lightweight, affordable package.   The TI-84 Plus C Silver Edition calculator before disassembly The battery has been removed from the rear of the calculator. It is a 1,200mAh, 3.7V rechargeable battery. The back of the calculator and the foil PCB shield have been removed. The CPU, memory, and other key parts are now visible. The keypad is exposed. The single rubber membrane that presses on the exposed electronic contact switches is removed from the body. The main PCB. Capacitors, circuitry, inputs, connectors, and chips are visible. The memory chip, which is used for RAM and storage. Also, the ribbon-cable display connector that connects to the LCD. The calculator’s processor. It is a model T6TX7AFG-0002 CPU, made by none other than Texas Instruments. Left - power jack Right - Mini USB charging port The two golden contact points on the PCB are used for charging the calculator with a dock, rather than the miniUSB cable. The LCD module, removed from the main PCB. The LCD itself, with no filters removed. One of the two polarizing filters used to direct the backlight directly into the LCD.   LCD Filters & Glass Cover LCD & PCB Calculator Keypad Battery & Cover Foil Shield & Display Cable