Browse Prior Art Database

Touchpad Indicator LED

IP.com Disclosure Number: IPCOM000061020D
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Connors, BJ: AUTHOR

Abstract

This article describes a circuit arrangement and method utilizing a light-emitting diode (LED) for indicating low battery power and circuit self-test in a touchpad unit. A single LED (yellow) is positioned behind the front lens of the touchpad. Low battery is determined by the low battery sense circuit illustrated in the block diagram in Fig. 1. A voltage potential is presented to the analog-to-digital (A/D) converter so the microcomputer can determine if battery power is low enough to start blinking the LED. When the battery voltage from the cells gets below approximately 4.5 volts, the LED blinks at a one-second rate, indicating to the user that the batteries need replacement. Infrared transmission stops when the low battery threshold is reached, signalling to the user to observe the LED indicator.

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Touchpad Indicator LED

This article describes a circuit arrangement and method utilizing a light-emitting diode (LED) for indicating low battery power and circuit self-test in a touchpad unit. A single LED (yellow) is positioned behind the front lens of the touchpad. Low battery is determined by the low battery sense circuit illustrated in the block diagram in Fig. 1. A voltage potential is presented to the analog-to-digital (A/D) converter so the microcomputer can determine if battery power is low enough to start blinking the LED. When the battery voltage from the cells gets below approximately 4.5 volts, the LED blinks at a one-second rate, indicating to the user that the batteries need replacement. Infrared transmission stops when the low battery threshold is reached, signalling to the user to observe the LED indicator. The LED will only blink when there is a touch down on the pad. This feature ensures that the battery potential does not decrease significantly enough so that it will not have the capability of powering the LED. Fig. 2 is a flow chart of the method used for indicating low battery and the technique followed for self-test of the LED. A test of the electronic card inside the touchpad unit occurs initially when the cable is plugged into the touchpad and when new batteries are placed in the touchpad without the cable attached. The same LED used for low battery will blink once, indicating that the electronic card self-test was passed.

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