BI_COLOR_INDICATOR

Published:2009/6/16 22:36:00 Author:May | From:SeekIC

With S1 open, base bias is supplied to Q2 through avoltage divider (formed by R2 and R3), thus turning on the green element in the LED. That indicates that power is being supplied to the project.Ifyou close S1, current through RI biases Q1 on, thereby grounding the voltage divider and turning off Q2. That reverses the flow of current through the LED, which causes its red element to light. That indicates that the circuit is under power and S1 (really a DPDT switch), whose remaining section controls another circuit, is active. In this circuit, a bi-color LED is used to indicate when a circuit is under power and the status of S1. In that way, the LED does the job of two indicators.



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