Scientific Calculator

Scientific calculatorsare more than just a necessity for every engineer. Filled with features that are able to deal with complicatedtrigonometric, exponential, and logarithmic issues in a blink of the eye. scientific calculators are nothing more than a small pocket brain. Find out the secret behind what makes this compact device perform.

Fig. 1: Image of an Scientific Calculator Most of the scientific calculators, irrespective of the manufacturer, are housed in a tough plastic casing like described above. The layout of the buttons is tidy and ergonomic , so that calculators can be used for a long periods of time without risk of straining the wrist. Additionally, they ensure an accurate keystroke every time, no matter the size of the fingers that press them.

PCB

Fig. 2. Circuit Board and LCD Display of a Scientific Calculator A plastic casing houses the PCB, batteries and screen of LCD on the calculator. A double-sided PCB can be utilized in a scientific calculator. On one side is the COB IC and the necessary circuitry and connections to an LCD The other side creates the keypad that houses the tracks that generate signals corresponding to the keys pressed. The rear of the PCB can be seen below.

Fig. 3: Chip on Board Integrated Circuit

Processing Core: COB IC or no COB?

Fig. 4. Integrated Circuit of Scientific Calculator Using a COB IC is an economical option since it can save significant amounts of hardware and is able to perform all the functions that are available to the calculator however, it usually eliminates the capability of that calculator to be user programmable. This also spells the difference between an ordinary, off the mill pocket calculator used for simple multiplication and adding purposes and a high-end scientific calculator that can handle a variety of computation. COB ICs are typically utilized in calculators that are not programmeable. However, those calculators that are programmable do come with a Packaged or Surface mounted microprocessor based IC which is connected to an external memory flash. Programmable calculators can be instructed to store user-defined information and formulas. The chip is not evident when used in scientific calculators too as that will also look like an COB IC due to the fact that the chip is covered with an epoxy coating. A few of the suitable ICs that have been employed in programmable calculators are the 8502 Microprocessor which was used within HP's 35s range of scientific calculators and the ARMv4T chips that are used in more powerful calculators , which include graph plotting capabilities and support for inputs to memory externally such as memory cards.

Keypad

Fig. 5. Keypad and circuit board from Scientific Calculator Shown in the image above is the reverse side of the plastic keyboard and PCB. Designs are drawn on the PCB's surface, which generate the signal for the keypad that is pressed. The signal is then convey in to the COB IC. Keypads function the same way that a keyboard does. The plastic switches on the casing are connected to a keypad made of rubber. When the key is pulled, the black rubber marker under that keypad's rubber reaches to the PCB. This creates the track to transmit signals.

LCD Display

Fig. 6: LCD Display and the Functions based on the capabilities included in the calculator, LCD screens in the calculator can be of different sizes and styles. For a basic calculator, it has a 16X2 LCD display, the ones enabled with advanced features feature an touchscreen LCD, too. Advanced scientific calculators even have a vibrant display.Shown in the photo above is a two line display LCD. The top line is an Dot matrix LCD display. While the lower one is an LCD display with seven segments of digits. The LCD is connected to the PCB by the aid of a heat seal connector. The term "heat seal" refers to a light connector made out from polyester films. Two polyester films are held (sealed) together at high temperatures with conductive paste that is the reason for the name heat seal.

Batteries

Fig. 7: Battery Combination of Scientific Calculator The type of batteries used depends on the features of the calculator. With more features or a larger size of displays on the LCD, the more efficient the battery will be. Above is an AA pencil cell combination that provides power to the calculator. Button cell and "AAA" batteries are also used in many calculators. The life expectancy of a battery pack is about 1-2 years (though it is different for each type of battery, and also from calculator to calculator). Incorporating a solar panel increases the life of the battery to the point that the primary reason for replacing the calculator isn't the depletion of batteries, but rather something related to physical harm due to falling it from a certain height. Moreover, calculators run on very little power and do not run dry as easily. In order to consume least possible battery power, they have an auto Power Off feature. This feature is controlled using a "Power Control Consumption System" which turns off the calculator in the event that no key is used during a predetermined time. Usually this time is approximately 7-9 minutes. If the calculator is currently in the middle of calculation (which is rarely the case) it saves the data for ease of the user.The first calculator that was scientific in nature was created in the late decade of the 60s Hewlett Packard and numerous electronic companies followed. It was initially expensive and features limited Engineers have continued to squeeze many more features into this tiny space since the industry of manufacturing semiconductors continues to mature.


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