OHN3040U – OPTEK

The OHN3040U, manufactured by OPTEK, is a unipolar Hall-effect magnetic switch packaged in a through-hole TO-92 3-pin configuration. This device incorporates a Hall-effect sensor, signal conditioning circuitry, and an open-collector output. Functionally, the OHN3040U activates (output switches low) when a magnetic field of sufficient strength and polarity (south pole facing the marked side of the package) is applied. The device remains activated while the magnetic field is present and exceeding the operate point (typically 30 Gauss). Upon removal of the magnetic field, the output deactivates (switches high) when the field falls below the release point (typically 10 Gauss), exhibiting inherent hysteresis to prevent output oscillation. The open-collector output requires an external pull-up resistor for proper operation and allows for interface with various logic families. It is typically used in proximity sensing, position detection, and speed sensing applications.