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Optical Mouse IR LED Mod Written by AidanII (25/Nov/02) Page 1 of 2
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Untitled Document
I've had a wireless optical mouse for ages. Never been bothered to
make any changes to it, and just used it as is. I remember when the first
batch of LED changes came out, people swapping out the red LED for
a blue LED. Cool, I guess, as long as your mouse works as well afterwards.
Unfortunately, most optical mice are not so sensitive to blue! Anyway,
I finally decided that my mouse needed to be different.
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The victim of this operation is a Trust wireless optical mouse.
It's been fairly reliable, except when used on certain blue surfaces. (Like
my mouse mat!). Red is boring, so I needed to choose another colour.
Handily I have a number of LEDs just sitting around on my desk, waiting
for something to happen. See? |
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| Choosing an LED should be simple really. In that little selection
I have two types. One is an amber LED. That's no good! The rest of
them are Infrared. Now, IR is invisible to the naked eye, but not invisible
to the sensor in the mouse. In fact, the sensor in the mouse is probably
more sensitive to IR than to red light!
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| First things first, the single screw holding everything together has
to come out. A quick grab of the leatherman, and there's little resistance
offered. Strange, there's no sticker saying "No user serviceable
parts inside". Yes, the batteries are still inside. It just makes
things more interesting! Note the red LED shining at the scroll wheel.
That illuminates to indicate the batteries are running low. There's also
two crystals at the bottom of the picture. They select the frequency the
mouse transmits on. It's just a simple switch that changes between the
two of them! It's difficult to see, but there is a separate circuit board
underneath, which houses the LED and sensor.
The next logical step is to remove the boards from the mouse without
breaking them. Before that happens, the batteries need to come out,
as they're currently holding the top board in place!
The two boards are connected together with a standard connector. They
need to be separated before work can commence on changing that all important
part, the LED. |
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As you can probably see, there's lots of stuff inside. The
top board has the little microcontroller on it that deals with generating
the messages and transmitting them to the base station.
The bottom board just concerns itself with the optical sensor and the
input switches. Yes, there are five on this board! Under the big white
blob is the optical sensor itself. The sticker helps to prevent light
getting in the wrong side of the sensor. Below the sticker is a black
plastic plate which houses the LED. The plastic is to ensure that the
LED only illuminates the surface under the mouse, rather than trying to
throw light directly into the sensor. |
| The plastic plate is held on by two small lugs on the bottom,
which slot into the two holes on the PCB. Once the LED is bent upwards,
the plate can be removed, leaving a clear view of the LED. You can also
see the top of the optical sensor more clearly. I have no idea why
there are holes in the top of the sensor packaging. Somewhat unsurprisingly
there is a hole in the bottom however, to allow the light in!
The next step is to desolder the existing LED, ready for the new LED
to go in. For that, more tools are needed. |
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