Help! - I Can't Scroll With My Mouse!
The Wheel on My Mouse is Not Working Properly?
Mice can be optical or use a roller ball. They can also be corded or cordless. However most mice nowadays have a scroll wheel which allows users to scroll up and down a webpage, image or document. When the scroll function fails totally or scrolling becomes erratic, the cause can often be due to dust and fluff which has made its way into the wheel.
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How Does the Scroll Wheel Work?
The scroll wheel in a mouse is a little like a bicycle wheel with "spokes" and "slots", however the spokes are somewhat thicker. An infra-red LED shines a beam axially (i.e. parallel to the axle) through the wheel, and the beam is picked up by an infra-red sensor (probably a photo-transistor) on the opposite side of the wheel. As the wheel turns, the spokes repeatedly break the beam so that the output signal from the phototransistor is a pulse waveform. This signal is then processed by an integrated circuit and sent to the computer. The frequency of the pulses increases when you roll the wheel faster with your finger (because the beam is being broken more often), so this results in faster scrolling on-screen. Non optical, i.e. roller ball mice, use the same system for detecting the motion of the ball, and also the scroll wheel.
Why Does Scrolling Stop Working?
Over time, crumbs and fluff from clothing, upholstery, bed linen etc gets transferred from fingers to the scroll wheel and makes its way inside the mouse. Also the wheel can become sticky or oily from contaminated fingers, which causes stuff to accumulate faster, compounding the problem. All this grime can block the slots, interrupting the infra-red beam, so that the signal from the sensor is not a nice clean pulse waveform. The result is non-smooth scrolling of the display.
How to Dismantle a Mouse
Mice like many electronic gadgets have an outer shell composed of two parts held together by screws. The screwheads may be visible, or hidden under pads which need to be peeled off first.
This guide specifically deals with a Microsoft Wireless Notebook Optical Mouse 4000, however the wheel in other mice won't be vastly different, maybe just clipped down in a different manner.
Remove the Battery
Remove the battery before you dismantle the mouse.
Warning - Static Can Damage Sensitive Electronics!
Walking over carpets or linoleum floors while wearing shoes or trainers with PVC soles can generate lots of static electricity, especially in dry weather, or if the air is dry inside from heating/air conditioning. You probably know all about this if you've ever got a shock when you touched a door handle or metal object. Static can destroy electronics, so just before you handle a circuit board, touch your finger against an earthed (grounded) metal object, e.g. a radiator or metal cased appliance. This will drain charge from your body. You can also use a ground strap which fastens around your wrist. See this Wikipedia link for an article about antistatic devices and ground straps
Cleaning the Wheel
You can remove bits of fluff with a small screwdriver, tweezers, piece of thin wire or whatever. A small air compressor and blow gun are very useful for cleaning parts/equipment and do a great job at blowing away this sort of stuff. You can also buy cans of compressed air (known as air dusters) which do the same job as an air compressor. Once you've done this, it's a good idea to spray the wheel with IPA (). This removes oils and grease. Alternatively wash the wheel in warm sudsy water, rinse and allow to dry. Once you've done this, replace the wheel, screw the cover back onto the mouse, and you're ready to go, everything should work fine again! isopropyl alcohol