Optical Mouse

We are back with the Disassemble series. This time with an optical mouse. We will try to figure out how the optical mouse works.

Tools of the trade.

We open up the mouse

and the insides plop out.

The LED that you see in the image below is the source of the red light that you see under the mouse.

The plastic “thingy” has a convex lens that directs the light from the red LED and directs it downwards.

There is another convex lens on the thingy, seen as the round dent in the image below.

The lens gathers the reflected light from the surface on which the mouse is resting. The light goes into a small hole pointed in the image below on the underside of the mouse.

The light goes into the hole which is part of a microchip. The chip is basically a very sensitive signal processor that continuously compares the images sent in through the hole and compares it with the previous images to identify the movement of the mouse.

This LED is just to light up the scroll button. Just above the this LED is the middle button below the scroll wheel.

The red thing pointed is compressed when the left mouse button is pressed.

Scrolling the mouse wheel turns this contraption which in turn translates that into signals that the laptop can understand.

A simple collection of a couple of LEDs, one of which is just for show, and a microchip is what it takes to move that versatile little pointer on your whim.

The Repellent

For my first post in the disassemble series I am going to look inside a simple All Out Mosquito Repellent.

The device appears to be working with its light glowing as seen in the below image.


But the device does not work as concluded by all the bite marks on my body and an absence of smell of the liquid. Note that in the image I have removed the bottle that contains the repellent liquid.Repellent2

The underside with the screws.

Opening up the device

Further disassembly

Going even further

So basically the device consists of a pair of aluminium rings separated by insulating material and a resistor. The resistor is color coded probably Red – Violet – Gold/brown – Blue — Which makes it either 2.7 ohms or 270 ohms with a tolerance of +/- 0.25% 🙁 The colors are not very visible. Its more likely to be 270 ohms.

What I dint get is what is that circularish, brownish object between and above the two aluminium rings. I don’t know its function.

Learnings from this experiment:

I need better tools. May be a plier and some other tools. Also some electrical measuring instruments like a multimeter. Also as I progress from electrical to electronic instruments, my knowledge would be woefully inadequate to deal with the complexity.