Browse Prior Art Database

Keyboard Tester

IP.com Disclosure Number: IPCOM000041998D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Duffy, DD: AUTHOR [+5]

Abstract

The force detector on the keyboard tester requires a near linear waveform detector. Waveform detectors cannot detect near linear waveforms. Ideally, the force applied to a key button on the keyboard should result in a linear waveform, as shown in Fig. 1, where P is the point at which the key spring buckles and a force value must be captured. Due to sticking, spring variations, etc., the actual waveform seen by the tester is approximated in Fig. 2. Using the standard peak detector, point A or B would be sensed as the "peak" value, stopping the search before the real peak is found at point P. The peak differential in the waveform is small at points A and B when compared to the value at P. This difference is the key to the near linear peak detector operation.

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Keyboard Tester

The force detector on the keyboard tester requires a near linear waveform detector. Waveform detectors cannot detect near linear waveforms. Ideally, the force applied to a key button on the keyboard should result in a linear waveform, as shown in Fig. 1, where P is the point at which the key spring buckles and a force value must be captured. Due to sticking, spring variations, etc., the actual waveform seen by the tester is approximated in Fig. 2. Using the standard peak detector, point A or B would be sensed as the "peak" value, stopping the search before the real peak is found at point P. The peak differential in the waveform is small at points A and B when compared to the value at P. This difference is the key to the near linear peak detector operation. The circuit developed uses an operational amplifier at the input to the peak detector (Fig. 3). The bias required to switch the state of the peak detector is set by RB, which is set to a delta value near the peak change expected at the spring buckle point. The small changes noted at points A and B are too small to overcome the detector bias. The same type of circuit is required to catch the spring unbuckle point, except the polarity of the change is reversed, and is of a much smaller value. The AML (Advanced Manufacturing Language) language was too slow to provide start/stop testing of the keyboard. Snapshot registers were utilized to capture data on the fly of up to 4 data values. The system requirements for the keyboard tester specify...