Abstract: A device is provided. The device includes one or more of a radially-wound coil, a hall-effect sensor, a power source, and a control circuit. The radially-wound coil is configured to produce a first magnetic field in response to a periodic current applied to the coil. The hall-effect sensor includes a sensor output that indicates proximity of a magnet to the hall-effect sensor. The magnet provides a second magnetic field and the sensor output indicates proximity in response to a combination of a strength of the first magnetic field and a strength of the second magnetic field exceeds a trip level. The coil is in fixed proximity to the hall-effect sensor, and the current is configured to control a polarity of the first magnetic field to detect the magnet. The power source is coupled to the hall-effect sensor, and is configured to provide power that alternates between on and off voltages to the hall-effect sensor.

Abstract: A device is provided. The device includes one or more of a plurality of sensor/light source groups, each including a sensor, a first light source of a first color, and a second light source of a second color, arranged in sequence along an expected direction of travel of an object. The device also includes a device to track objects, coupled to the plurality of sensor/light source groups, and configured to drive first light sources in response to playback of a stored sequence and drive second light sources in response to received active sensor outputs from sensors of the plurality of sensor/light source groups.

Abstract: A device is provided. The device includes one or more of a radially-wound coil, a hall-effect sensor, a power source, and a control circuit. The radially-wound coil is configured to produce a first magnetic field in response to a periodic current applied to the coil. The hall-effect sensor includes a sensor output that indicates proximity of a magnet to the hall-effect sensor. The magnet provides a second magnetic field and the sensor output indicates proximity in response to a combination of a strength of the first magnetic field and a strength of the second magnetic field exceeds a trip level. The coil is in fixed proximity to the hall-effect sensor, and the current is configured to control a polarity of the first magnetic field to detect the magnet. The power source is coupled to the hall-effect sensor, and is configured to provide power that alternates between on and off voltages to the hall-effect sensor.

Abstract: A device is provided. The device includes one or more of a plurality of sensor/light source groups, each including a sensor, a first light source of a first color, and a second light source of a second color, arranged in sequence along an expected direction of travel of an object. The device also includes a device to track objects, coupled to the plurality of sensor/light source groups, and configured to drive first light sources in response to playback of a stored sequence and drive second light sources in response to received active sensor outputs from sensors of the plurality of sensor/light source groups.

Abstract: A device is provided. The device includes one or more of a radially-wound coil, a hall-effect sensor, a power source, and a control circuit. The radially-wound coil is configured to produce a first magnetic field in response to a DC current applied to the coil. The hall-effect sensor includes a sensor output that indicates proximity of a magnet to the hall-effect sensor. The magnet produces a second magnetic field and the sensor output indicates proximity in response to a sum of a strength of the first magnetic field and a strength of the second magnetic field at the hall-effect sensor exceeds a trip level. The radially-wound coil is in fixed proximity to the hall-effect sensor. The power source is coupled to the hall-effect sensor and is configured to provide power that alternates between on and off voltages to the hall-effect sensor.

Abstract: A device is provided. The device includes one or more of a radially-wound coil, a hall-effect sensor, a power source, and a control circuit. The radially-wound coil is configured to produce a first magnetic field in response to a DC current applied to the coil. The hall-effect sensor includes a sensor output that indicates proximity of a magnet to the hall-effect sensor. The magnet produces a second magnetic field and the sensor output indicates proximity in response to a sum of a strength of the first magnetic field and a strength of the second magnetic field at the hall-effect sensor exceeds a trip level. The radially-wound coil is in fixed proximity to the hall-effect sensor. The power source is coupled to the hall-effect sensor and is configured to provide power that alternates between on and off voltages to the hall-effect sensor.