ULTRA_SIMPLE_RS232_TESTER

Published:2009/7/12 21:05:00 Author:May | From:SeekIC

The tester consists of no more than a two-color LED (or a red and a green LED connected in anti-parallel) in series with a 1-kΩ resistor. The free ends of the resistor and the LEDs should preferably be terminated in 1-mm plugs. One of the free ends should be covered in green sleeving, or use a green 1-mm plug. This is touched on pin 7 (signal ground) of the connector under test. The other end is touched on each pin to be tested, in turn. The LED (or LED pair) is connected so that a positive voltage emits a red glow and a negative voltage causes a green glow. Sometimes, an RS232 input will be found that has an internally connected pull-up to drive a particular default RS232 level when unconnected. Although this will cause the tester to glow as if the pin were an output, it will do so with markedly less brightness. Bearing this in mind, the tester can be used to diagnose most RS232 problems at the electrical level.



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