How does a laptop touch pad work?
The grid of wires is how stylus touch pads work, like a PDA or and iPod Touch, laptop mouse touchpads usually use heat to detect touch, which is why it doesn’t work as well (i.e. skips a bit) when your hands are very cold. The difference in usage is that the heat touchpads cannot easily be made transparent, and are very low resolution, but cheaper to make. The low resolution means that you need to use a larger object to contact them in order to get a good result, such as a finger rather than a stylus. The conductivity pads are much higher resolution, and can be two transparent layers (one flexible film and one the hard glass) that can detect a much smaller and precise contact. You can tell the difference between the two by tapping it gently. If you hear a normal hard surface tap, it’s a heat sensitive pad. If you hear a noise almost like two distinct clicks, it’s a conductivity sensitive pad.
Hey folks, Most of the above answers are correct in terms of touchpads through history, they have all worked on gird array’s of wires, thermal pickups etc throughout the evolution of the devices, but duffmean has come the closest to it so far. Nowdays, 99.9% of laptops use capacitance pads. This is a system where wires are overlaid across each other, but the change in capacitance when your finger moves over is what triggers the pad. A capacitor consists of 2x main elements, the plates and the dialectric (being some sort of material that interferes with current flow between the plates, electrolyte in an electrolytic capacitor for example, tantilum in a tantilum capacitor etc). Imagine 2 metal plates about an inch apart, with power flowing through them. If you place an object between the plates, the capacitance will change as you are effectivly modifying the distance between the plates by adding mass (those who have ever pulled the guts out of a valve radio will be familiar with the rota
On the subject of how does a touchpad know when you touched it. There are different methods and materials that can be used. If you want the technical answer then you go to http://www.patentstorm.us/patents/5521336.html for a specific patent. Other patents exist for touchpad technology. If you don’t have an electronics background, then it is probably much more than you really wanted to know. The following is incorrect but it does give you the basic idea of how it works. If you want to know how it really works then you should read the patent for the touchpad you want to know about.. Think of a touchpad as a grid of wires that cross each other but are not touching each other. There is a low conductivity material between the wire intersections so that electricity does not flow between the wires. When you press on it, the material get’s thinner between the wires which when thin enough will allow elec
The touchpad, as I believe it, is comprised of overlaying wires, as someone had said before. But as the wired touch, they need a magnetic source to tell the laptop that something magnetic is touching it. I don’t know… Why doesn’t someone try to put a magnet next to their laptop and see if it works. There is only one weird thing with that theory. I tried the touchpad with my fingernail, and it didn’t work. As far as I know, bone doesn’t stop a magnetic field.
