Proximity switch integrated circuit composed of the magnetic field sensor HMC1001

The circuit depicted in the figure includes the HMC1001 magnetic sensor, an operational amplifier (AMP04), and a light-emitting diode (LED), forming a proximity switch circuit. In this application, the operational amplifier functions as a comparator. When a magnet, approximately 6mm to 12mm in length, is brought close to the HMC1001, the output voltage of the MR bridge reaches 30mV, causing the comparator to flip and the output to go low, which in turn illuminates the LED. Conversely, when the magnet is removed, the comparator output switches to a high level, turning off the LED. This circuit effectively operates as a proximity switch with an indicator light, suitable for detecting displacement, speed, and other non-electrical variables. The threshold voltage of the switch can be adjusted by modifying the value of resistor R1.

The proximity switch circuit integrates several key components to achieve its functionality. The HMC1001 is a magnetic sensor that detects the presence of a magnetic field. When a magnet approaches the sensor, it generates a voltage output that is fed into the operational amplifier, which is configured as a comparator. The comparator compares the sensor output voltage to a preset reference voltage.

The operational amplifier (AMP04) is chosen for its precision and ability to operate in low-voltage scenarios. The output of the comparator is connected to the anode of the LED, while the cathode is connected to ground through a current-limiting resistor. This configuration ensures that the LED only activates when the output of the comparator is low, indicating the presence of the magnet.

Resistor R1 plays a crucial role in setting the reference voltage for the comparator. By adjusting R1, the sensitivity of the circuit can be fine-tuned, allowing it to respond to different strengths of magnetic fields. This feature makes the circuit versatile for various applications, including proximity sensing in automation systems, speed detection in moving objects, and other non-contact measurements.

The overall design of this proximity switch circuit is compact and efficient, making it suitable for integration into various electronic systems where space and power consumption are critical considerations. The use of an LED as an indicator provides immediate visual feedback, enhancing the usability of the circuit in practical applications. As shown in FIG grounds HMC1001 and an operational amplifier (AMP04) and light emitting diode (LED) constituting the proximity switch circuit. As used herein, the op amp as a c omparator. The length of about 6mm ~ 12mm magnet closer HMC1001, when moved to a certain position, MR bridge output voltage reaches 30mV, the comparator flip, output goes low the LED light. If the magnet is removed, the comparator outputs a high level so that the LED goes out. Obviously, this circuit is equivalent to a proximity switch with indicator light can be used to detect displacement, speed and other non-electricity.

Adjusting the value of the resistor R1 can set the threshold voltage of the switch.