Eugene is a qualified control/instrumentation engineer Bsc (Eng) and has worked as a developer of electronics & software for SCADA systems.
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 non double insulated metal cased appliance that is plugged in (for example a metal kettle or cooker/range) 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 (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!
Best Computer Mouse! — If your Mouse Still Won't Work, This is the One to Buy!
The mouse in the photos above is a Microsoft Wireless Notebook Mouse 4000. I bought it 8 years ago for my new notebook computer and it has never given any trouble. The touchpad on a laptop is fine for general use, but a mouse is much faster for navigating the cursor around the screen, and is practically essential for CAD.
The Microsoft Wireless Notebook Mouse 4000 is the "Goldilocks" of mice. Not too big, not too small, but fits comfortably under the palm. The scroll wheel turns smoothly without any resistance and there is no "bumpiness" or "clickiness" which I've noticed with other mice. A third auxiliary button on the side of the mouse can be programmed for any function as can the left, right button and scroll wheel. The scroll wheel can be clicked also which is pretty much standard on mice. This mouse isn't available on Amazon any more, but the upgraded version is the Microsoft Wireless Mobile Mouse 4000
By the Same Author
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
© 2016 Eugene Brennan
Eugene Brennan (author) from Ireland on May 05, 2020:
Thanks for the comments. Blowing can shift dust and sort the problem.The clogging up can take years to happen so it'll probably sort your problem for some time anyway.
SMARTIN on May 04, 2020:
Hi Eugene... I may have over simplified my repair technique... after reading comments I blew into the wheel from above (assembled from above the wheel) and also changed the USB port it was plugged into... seems to be working. thanks for your "how it works" or I would have never tried this. hope it helps as a first result?
Nothing here on December 29, 2019:
If it's a usb mouse, try plugging the usb into a different slot. Worked for me.
Dee Hechtor H on March 17, 2018:
Thank you so much, my mouse scroll wheel just stopped scrolling, just like that. This post informed me on the inner workings of a mouse and fix my mouse in about 10 minutes. Thank you.
Eugene Brennan (author) from Ireland on December 04, 2017:
Emanuel it could be a resolution issue, because Hall-effect magnetic encoders don't give the same fine control as an optical type. Magnetoresistive encoders are available, that give better resolution, but optical sensors are cheap and simple so that's probably why they're used.
Eugene Brennan (author) from Ireland on December 04, 2017:
Thanks Diana, glad it helped!
Diana Jones on December 04, 2017:
At first I thought my computer was hit by virus. my mouse cannot scroll like usual and distorted. thanks to your explanation my mouse back to work again. thank you.
Emanuel Bucsa from Baia Mare, Romania on November 10, 2017:
I'm wondering why they don't just replace the optical encoder with a mechanical encoder (rotary encoder?). I mean if dust is the issue, wouldn't it make sense to replace the part that frequently causes these kinds of issues with a part that's mostly unaffected by dust?
Just my two cents here :)
Louise Powles from Norfolk, England on July 20, 2017:
Well that was interesting to read. I always use a wired mouse, and would never attempt to fix one! I'd probably end up breaking it more lol. I would rather just get a new one.
Eugene Brennan (author) from Ireland on January 23, 2017:
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.
chau nguyen on January 23, 2017:
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.
Eugene Brennan (author) from Ireland on January 19, 2017:
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.
evan on January 19, 2017:
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
Eugene Brennan (author) from Ireland on January 12, 2017:
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.
James on January 06, 2017:
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.
Eugene Brennan (author) from Ireland on June 19, 2016:
John Hansen from Gondwana Land on June 18, 2016:
Very comprehensive advice for keeping your mouse scrolling smoothly, Eugene. Good clear pics too. Well done.