N＋1WIRES_CONNECT_N_HALL_EFFECT_SWITCHES

Published:2009/7/10 5:03:00 Author:May | From:SeekIC

Hall-effect switches have several advantages over mechanically and optically coupled switches. Their major drawback is that they require three wires per device. This circuit, however, reduces this wire count to N + 1 wires for N devices.Amplifter IC1A is configured as a current-to-voltage converter. It senses the sensor assembly's output current. When the Hall-effect switch is actuated, the sensor's output current increases to twice its quiescent value. Amplifter IC1B, conftgured as a comparator, detects this increase. The comparator's output goes low when the Hall-effect switch turns on.The circuit also contains a fault-detection function. If any sensor output wire is open, its corresponding LED will turn on. If the power-supply line opens, several LEDs will tum on. A short circuit will also tum an LED on. Every time an LED tums on, Q1 turns on and the alarm relay is actuated.



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