LEDs light LAN-cable tester
Noureddine Benabadji, University of Sciences and Technology, Oran, Algeria; Edited by Martin Rowe and Fran Granville - December 2, 2010
Cable and connector faults are relatively common in LANs (local-area networks). You can use the circuit in Figure 1 to test straight- or cross-link 10BaseT, 100BaseT, or gigabit UTP (unshielded-twisted-pair) and STP (shielded-twisted-pair) cables. The circuit performs a continuity test for each linked pair. An LED representing each linked pair flashes when the corresponding pair connects properly between the cable’s RJ-45 connectors. It can also determine whether the cable is a straight-link or a cross-link type.
IC1, a small, six-pin Microchip PIC10F200 microcontroller, performs the test. On power-up, the four I/O pins act as outputs and are driven high for approximately 0.5 second and then are driven low in the following sequence: GP0, GP1, GP2, and GP3. Once this task finishes, the microcontroller has a dead time for about 4 seconds, after which it loops to the beginning to repeat the procedure.
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