Edge detection is always an interesting field for researchers in the area of artificial intelligence, including machine visions and robotics. In the context of tactile sensors, many studies have been conducted on edge-identification algorithms. These investigations often use high-resolution tactile sensor arrays to track an edge of a large object. In this work, edge identification is examined in which a coarse-resolution tactile sensor, specif., a 2${ imes}$2 array, is used to detect and track edges of a small object. To simplify the control, we control the sensor just in 2D and in just one direction at a time. We propose two methods to solve this problem: a scanning method, of which the principle of operation is similar to that of a scanner, and an edge-following method that can make the sensor follow the boundary of the object. The flowchart of each method will be presented in detail in this paper. Some simulations in MATLAB, including four shapes, viz., square, triangle, ellipse, and hexagon, have been executed to verify our proposal. A comparison and a critique of the two methods are also presented for improving the methods.