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Help! - I Can't Scroll With My Mouse!

Updated on February 27, 2017
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Eugene is a qualified control/instrumentation engineer Bsc (Eng) and has worked as a developer of electronics & software for SCADA systems.

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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.

The scroll wheel spokes and slots repeatedly make and break the beam, so the sensor generates a pulse signal
The scroll wheel spokes and slots repeatedly make and break the beam, so the sensor generates a pulse signal | Source
Pulse signal from infra red detector
Pulse signal from infra red detector

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.

Remove the battery!
Remove the battery! | Source
The screws holding this Microsoft optical mouse together, are hidden under pads
The screws holding this Microsoft optical mouse together, are hidden under pads | Source
Peel or poke out the pad with with a screwdriver
Peel or poke out the pad with with a screwdriver | Source
Remove the screws
Remove the screws | Source

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

Anti-static warning
Anti-static warning | Source
Touch your finger off a grounded (earthed) appliance such as a radiator to drain charge from your body before handling electronic components
Touch your finger off a grounded (earthed) appliance such as a radiator to drain charge from your body before handling electronic components | Source
Antistatic wrist strap with a crocodile clip for connecting to ground
Antistatic wrist strap with a crocodile clip for connecting to ground | Source
Inside the mouse
Inside the mouse | Source
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The infra-red LED shines a beam through the wheel
The infra-red LED shines a beam through the wheel | Source
Lever up from the front with a small screwdriver......
Lever up from the front with a small screwdriver...... | Source
......and pull up with your fingers
......and pull up with your fingers | Source
Next lever up from the back
Next lever up from the back | Source

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 (isopropyl alcohol). 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!

This wheel is clogged with fluff and crumbs
This wheel is clogged with fluff and crumbs | Source
After cleaning
After cleaning

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    • Jodah profile image

      John Hansen 9 months ago from Queensland Australia

      Very comprehensive advice for keeping your mouse scrolling smoothly, Eugene. Good clear pics too. Well done.

    • eugbug profile image
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      Eugene Brennan 9 months ago from Ireland

      Thanks Jodah!

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      James 2 months ago

      Why would scrolling up work but scrolling down doesn't (sometimes it does for about 2 cm, sometimes not at all)?

      I've tried it on 2 computers.

    • eugbug profile image
      Author

      Eugene Brennan 2 months ago from Ireland

      Hi James,

      Is the mouse a roller ball or optical type?

      Cleaning the rollers and roller ball with meths or IPA removes any grease/fluff which can prevent the rollers from turning.

      I'm not quite sure how roll direction is worked out for the scroll wheel. For roller ball mice, two sensors are used for each of the encoding disks for x and y movement of the roll ball. My mouse seemed to have one sensor for the scroll wheel, but there may be two active elements built into the casing of the sensor. Sometimes a plate is used between sensor and disk/scroll wheel so that each sensor gives either a high or low state when th second sensor transitions. Check whether this is obstructed or if the sensor is loose on the circuit board.

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      evan 2 months ago

      my mouse problem is very different, i have 4 different mouses, all of them work, all of them new but my pc wont detect the scroller

    • eugbug profile image
      Author

      Eugene Brennan 2 months ago from Ireland

      Hi Evan,

      Launch Control Panel, go to mouse settings, then the buttons tab and check whether "connected device" corresponds to your device.

      Under the scrolling tab, check whether scrolling is enabled.

      These setting layout may be slightly different depending on your operating system and mouse type.

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      chau nguyen 2 months ago

      sincerely thank you, u just save me from buying new mouse. btw, there's a better way to do it, using ear swap and clean the scroll from the outside, without dismantling the mouse ^^

      and i also use metal staples or paper clips to take all the excess dirt inside.

      but, ur instructions are still tremendously helpful.

    • eugbug profile image
      Author

      Eugene Brennan 2 months ago from Ireland

      Thanks Chau! - You can clean the perimeter of the wheel without dismantling but can do a better job if the cover is removed. Depending on the design, the slots may be shrouded from access (like the mouse above) but if you can get a paper clip into the gap you may get some of the fluff out. The battery should be removed also to prevent shorting anything out.

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