Solution to Phantom Key Problems
Original Publication Date: 1985-Oct-01
Included in the Prior Art Database: 2005-Feb-19
This article describes a technique to minimize phantom keystrokes connected with a keyboard switch matrix of rubber-dome switches which function as regular on-off switches. When using a switch matrix of rubber-dome switches, however, there appears the problem of phantom keys. A phantom is a key that appears down to the sensing circuitry but in reality is not. Whenever there are three keys down which form an electrical rectangle in the matrix, it looks to the driving circuitry that the fourth key is down, as illustrated in Fig. 1. In order to correct this problem, a three-part solution is disclosed herein consisting of a process of choosing an optimal array, designing a matrix layout which minimizes the phantom occurrence, and software for accomplishing the result.