Electronics Optical Mouse Dissection Essay

For the “Take it Apart and Figure It Out” Project, Team Arsenic was given a wired optical mouse. The mouse brand was Onn, produced by Blue Trace Technology and sold by Wal-Mart. During the in-class part, we obtained a basic understanding of the workings of the mouse, but, to completely understand the operation of the mouse, we had to research the various parts individually since no blueprint for the mouse exists. After understanding the individual parts of the mouse, we figured out how they work together to scroll the cursor, move across web pages, and select options through the buttons of the mouse.

In order for the mouse to be powered, it must be plugged into a power source, as this is a wired mouse. In this case, the mouse receives power through the universal serial bus (USB) port. The cord entering the mouse has four wires; two are for power, and two are for data. The grey is the hot wire while the blue is the ground. For data transfer, green provides the incoming data stream while white provides the outgoing data stream. When the power enters, it immediately goes to the microchip. The microchip processes all operations of the mouse.

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It is responsible for all the responses the mouse makes to movements by the operator. The microchip also houses a semi-conductor, the importance of which will be explained later. Once power reaches the microchip, it distributes it to different portions of the mouse including two contact switches, a scrolling wheel, the switch on the wheel, and a light emitting diode (LED). Before reaching any of these portions of the mouse, however, the current must flow through a series of mica capacitors, electrolytic capacitors, and resistors.

In this mouse, five capacitors (two mica, three electrolytic) and one resistor control the current to the LED. The mouse contains two contact switches (push button switches) at the front for the left and right buttons. The operations of these devices correlate to its name. When pushed down, the plastic button presses a thin, flimsy slice of metal to the bottom metal strip, thus completing the connection with the other side. This circuit allows current to flow as long as the mouse button is pressed down.

After releasing the button, the circuit breaks and current no longer flows. Hence, the name “contact” switch. Another switch is located on the left side of the scroll wheel. A second variety of push button switch, this one alternately locks on and off when pushed, meaning it locks in the “on” position until pushed again. This switch controls an arrow scrolling option on the screen. When this icon appears, the operator can scroll in any direction in which the mouse is moved. The scroll wheel provides a method of scrolling up and down on web pages.

The operation of this wheel begins with the incoming power. One side has alternating contact points and plastic breakpoints so the wheel is not constantly making contact and scrolling. The other side has three metal wedge contact points split in two slightly protruding to make contact with the other side at appropriate places. To prevent the wheel from spinning freely, a small wedge is located at the side of the wheel housing, which causes the intervals when scrolling the mouse wheel.

As previously mentioned, the main control of the mouse, the microchip, contains a semi-conductor which provides a means for scrolling on the page. The LED, encased by a black box, projects light through the top magnification portion of the lens, which is reflected onto the surface on which the mouse is moved. This light reflects back off the surface into the lens where it magnifies the light and shoots into the semiconductor. Once in the semiconductor, the movement of the image is processed to determine speed of the movement as well as distance. This translates to the movement on the computer monitor.