Browse Prior Art Database

Embeded Touch Sensor for PC

IP.com Disclosure Number: IPCOM000011857D
Original Publication Date: 2003-Mar-20
Included in the Prior Art Database: 2003-Mar-20
Document File: 2 page(s) / 10K

Publishing Venue

IBM

Abstract

Disclose is a circuit for touch sensor which is embeded in personal computer.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 53% of the total text.

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Embeded Touch Sensor for PC

Main Idea: Standard personal computer has a super I/O chip which controls input/output devices(keyboard, mouse, floppy, printer, etc,.). And it also has several tachometer function to sense cooling fan speed. Ordinary personal computer's cooling fan generates pulse signal and the pulse frequency depends on rotation speed of the fan. Therefore tachometer can sense rotaion speed by counting pulse number per fixed period of time. This invention uses the tachometer as a circuit of touch sensor.

How this disclose works: General touch sensor consists of following four sections. #1. Pulse generator It generates pulse signal. #2. Sensor plate and filter If someone touches a sensor plate, plate's capacitance is changed by human body. Filter's characteristic is designed to use the change of capacitance as follows.

a) if touched, filter passes #1 pulse signal

b) if not touched, filter cuts #1 pulse signal #3. Signal smoother It makes #2 signal flat. If input is pulse signal(touched), flatted signal voltage is higher than non pulse signal(non touched).
#4. Comparater It compares #3 signal voltage to determine whether it is touched or not.

This disclose uses tachometer function instead of #3 and #4 circuit. Case-1: Embed touch sensor on personal computer's motherboard #1 and #2 sections are required on motherboard for this implementation. Output signal of #2 is connected with input of tachometer after signal arrangement between 0 and 5V. It is possible to use both of fan tachometer and touch sensor, if a gate logic is attached before tachometer input. In th...