The Technical Description of an Optical Computer Mouse

Simon Au

The City College of New York

ENGL 21007: Writing for Engineering

Professor C. Rodwell

April 5^th, 2020

 

 

 

 

Table of the Contents

Cover Page ……………………………..…………………………………………………………… 1

Table of Contents ………..………………………………………………….….…………………. 2

Introduction …………………………………………………………………………………………. 3

Inventors …………………………………………………………………………..……………….. 3

History of the Mouse …..………………………………………………………….………………. 3

Innovations on the Mouse …………………………………………………………………………. 3

External Parts ………………………………………………………………………………………. 4

Cord ……………………………………………………………………………..………..………… 4

Mouse Buttons ………….………………………………………………………………………….. 4

Mouse Shell/Case …………………………………………………………………………………. 5

Screw/Pad ……………………………………………………….….……………………………… 5

Internal Parts ……………………………………………………………………………………….. 5

Light ………………………………………………………………………………………………….. 6

Prism/Mirror …………………………………………………………………………………………. 6

CMOS Censor/Camera ……………………………………..……………………………………. 6

Microswitch/Spring …………………………………………….………………………………….. 7

Rotary Encoder ……………………………………………………………………………………. 7

Circuit Board ………………………………………………………………………………………. 7

How they connect? ………………………………………………………………………………. 8

Conclusion ……………………………………………………..…………………………………. 9

Reference Page ………………………………………………………………………………….. 10

 

 

 

 

 

 

Introduction

        The purpose of this paper is to inform the audience of the structure and inner workings of a Logitech M-UAE96 optical mouse. The paper will touch on topics such as the components, the function of each part, and how the parts works with each other. In addition, general information along with visuals will be used throughout the paper to better inform the reader of the product.

        To begin, the computer mouse that are commonly used today are known as the optical mouse (Fig. 1). These types of mice use a camera-like censor that tracks the movement of the mouse across the mousepad. However, this style was not commonly used until the recent decade. In the past, there have been various innovations, shaping the computer mouse to what it is today. Looking into the first computer mouse (Fig. 2) created in 1964, the inventor, Douglas Engelbart, created what was essentially just a wooden block with a circular disk to detect movement and a button for clicking. This bulky inefficient invention may seem unimpressive, but this first mouse created a spark in the invention and innovations to come for electronics. In 1974, the first major innovation for the mouse occurred, reducing the size and changing the shape of the overall mouse. In addition, two button mice started becoming more popular due to the convenience of right clicking. However, it was not until 1996 did the common two button and a scroll button mouse appeared in market. Created by Microsoft, the mouse was designed for the purpose of convenience as the scroll button would minimize the dragging needed to move a web page. In addition, it was around this time that a new type of mouse appeared in the market. Unlike the first models that used a disk, this new model uses a ball (Fig. 3). The ball mouse allows for easier mobility and allows for the mouse to be the size of your palm. Finally, in 2001, the first cordless mouse was created, allowing the mouse to move more freely. It was also around this time did the newest model, the optical mouse, rise in popularity.

   Figure 1 (Optical Mouse)

  Figure 2 (First Computer Mouse)

  Figure 3 (Mouse with Ball)

        Clearly shown throughout the timeline of the mouse, the need for innovation for a mouse revolves around simplicity sake and convenience. This means that all the modifications and improvements made since the first mouse targeted the consumer’s need for a more compact and simple style of mouse. Now, the paper will discuss each component of the latest type of mouse, the optical mouse.

External Parts

        An optical mouse has four main external components: the cord, the buttons, the shell, and the screws.

        The cord is essentially what connects the mouse to the computer, relaying information as well as what charges the mouse. Although the colors may vary, the most common color is black and usually extends to around 4-6ft in length. At one end of the cord attaches a USB which can be inserted to your computer (Fig. 4). The other end runs into the mouse and attaches to the circuit board which will be mentioned later in the paper. (Fig. 7 Wires)

        The typical mouse has three buttons which are the left mouse button, right mouse button, and the middle mouse button (Fig. 5). The left and right mouse buttons are exactly the same, but the shape is flipped across the y-axis. As for the middle mouse button, it is resting between the left and the right mouse button. The middle mouse button is different in that it is a wheel instead of a flat piece of plastic. As for the button’s underside, the three buttons have a little wedge below them and when pressed downwards, the wedge would hit the microswitch, which will be talked about in the microswitch section. Other than this, the three buttons are made of plastic and is slightly curved downwards to fit the shape of a hand.

        The shell, also known as the case, has two parts, the upper shell and the lower shell (Fig. 5). The shell is essentially two pieces of hard plastic, one of which curves to the shape of your palm (upper shell), and the other flat to glide across your mousepad (lower shell). The flat piece holds all the inner circuits and components while the curved part is to protect the sensitive parts within the mouse and a place to rest your hands while using the device.

  Figure 4 (Mouse Cord End)

  Figure 5 (Lower and Upper Shell)

  Figure 6 (Screw and Screw Hole)

        The screw and pads are the last external components of the mouse (Fig. 6). The screw is a one-centimeter screw that holds the upper and lower shells together. As for the pads, they are also known as Teflon pads and help in reducing resistance when moving the mouse. Looking at figure 6, you could see the lower pad with a slight white color to it.

Internal Parts

        The optical mouse has six main internal components: The LED light, the prism/mirror, the CMOS sensor/camera, the microswitch, the rotary encoder, and the circuit board.

        The LED lights serves two purposes for the mouse. The first is just for aesthetics, creating a glow that is popular in many gaming mice today. The second and more practical use is to light up the area below the CMOS sensor. In order to more accurately sense movement, lighting the area under the sensors will allow for better precision for the mouse. Looking at Figure 7, the yellowish part with a red dot is where the LED light is in. Figure 8 removes the hood to see the LED light turned on.

  Figure 7 (CMOS Sensor and LED Light Hood)

  Figure 8 (Close Up of LED Light and CMOS Sensor)

        The prism is essentially a semi-clear piece that is used to reflect and guide the light produced by the LED light to the bottom of your mouse (Fig. 9). It has a small lens at the end where it helps shine the LED light to the right place for the CMOS sensor to be able to sense movement. Figure 10 shows how the prism is used to reflect the light and will be discussed later.

        The CMOS sensor is one of the most crucial part for the mouse, serving as the eyes to track movement (Fig. 12 Black Square). Essentially, this is a cameralike sensor that would take in light and convert them into electrical signals. What this means is that it uses the light provided by the LED and takes thousands of pictures of the bottom of the mouse every few second. Upon moving, the pictures will track the movement, allowing for the CMOS sensor to convert the information to electrical signals and send it off to the digital signal processor located on the circuit board. Figure 10 shows how light would hit the CMOS sensor thanks to the prism.

Figure 9 (Prism)

Figure 10 (Diagram of LED shining through prism into CMOS Sensor)

        The microswitch is the next component and is basically the sensor that detects clicking of the mouse. The microswitch has a small metal strap on the top that would sense the slightest touch from the wedge under the mouse buttons. When pressed, the wedge would hit the metal strap, sending a signal that the button has been hit. There is also a spring under this metal strap to push the button back up, resetting the button. Each mouse button has its own microswitch, which can be seen on Figure 11, the three black rectangular pieces with a white bump on top.

        The rotary encoder is the next piece and essentially serves one purpose. This part is located on Figure 11, where you can see the small black box, parallel to the blue small box. This piece is similar to the CMOS sensor, but senses the direction of which the wheel goes. When you scroll up or down, the direction of the wheel is recorded by the rotary encoder and then sends the information to the circuit board. This part also measures the speed in which the wheel moves which sends signals of how fast the webpage should be moving up or down.

        The circuit board is the final component and the largest of all the components listed. Shown on Figure 12, the circuit board is the green board with all the wiring on it. This part provides the support for the electrical signals and information to pass on to other components. It is made of plastic, metal, and bits of silicon and in this case, holds the wires, CMOS sensor, LED light, resistors, capacitors, rotary sensors, and essentially all the important components on here.

  Figure 11 (Three Microswitches and Rotary Encoder)

  Figure 12 (Circuitboard)

        The capacitors are the battery like part which can be seen on Figure 11 on the upper right corner and Figure 7 on the upper left corner. They save energy by storing the electrical energy within this tube until it is needed. As for the resistors, they slow down the current in the circuit to create resistance and believe it can be seen on Figure 7, the wire part next to the middle mouse microswitch. All these parts are attached to the circuit, allowing for information to pass easily and for the mouse to function properly.

How They Connect?

       All these components work together and are all connected in some form. To begin, the buttons are attached to the upper shell, which is screwed down to the lower shell. A cord runs between a hole in the front of the shell, connecting to a white box through five wires shown on the upper right of Figure 7. The wires are then attached to the circuit board, which rests on the lower shell of the mouse. This wire would relay information between the computer and the mouse. Under the mouse buttons are the microswitches, that relay information to the rest of the circuit. The mouse button also has the rotary sensors next to the microswitch to detect movement on the wheel, sending signals directly to the computer. Towards the center of the board lies the CMOS sensor, which is attached to the prism and LED light. These parts work with each other to sense movement in the mouse, turning it into information for the computer. Basically, all this is compacted into a fist size mouse that people use in their everyday lives.

Conclusion

        To conclude, there are roughly 10 main parts of an optical mouse, all of which serves an important purpose in the function of the mouse. The components are dividing into three sections, the outer shell, the components that works with the buttons, and the components that sense mouse movement. These parts work on top of the circuit board, which is the brain in relaying information between the mouse and computer. Together, these parts make up the optical mouse in which every office building in NYC and most of the world uses every day. Although there are many more improvements that could be made in the future, the optical mouse today is the most innovative version of the mice available today.

 

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