The A3144 Hall Sensor is an electronic circuit that responds to an alternating magnetic field similar to a reed switch.
Hall Sensors are easier to adjust since the distance between sensor and magnet is not critical.
The Digital Hall Sensor device is a small integrated circuit, which has just two states, ‘On’ and ‘Off’.
Unipolar in its action, only requires a single magnetic South Pole (Hall Sensor face with writing on) to both operate and release them as they move in and out of the magnetic field.
The rear side can be activated with a North Pole magnet.
The IC contains a Hall Sensor that detects the magnetic field, a high gain amplifier and a Schmitt trigger to provide hysteresis.
When a magnet is passing the Hall Sensor, it will exceed the pre-set value of the output from the device to switch quickly between its ‘On’ condition to an ‘Off’ condition, without any type of contact bounce.
This built-in hysteresis eliminates any oscillation of the output signal as the sensor moves in and out of the magnetic field.
The A3144 Hall Sensor device cannot directly switch large electrical loads as the output drive capability is only 25 mA. For large current loads an open-collector NPN or PNP Transistor can be added to increase the output.
Despite the internal complexity, only three wires are required to interface with the outside world. The output is an open collector transistor, so a load resistor is required between the output and the positive supply.
When the device detects a magnetic field, the output voltage switches from supply voltage potential to ground potential, providing the correct input for a device, for example on a decoder, sound card, or to a Feedback Module.
Three different designs that are being used for connection to the Feedback Module.
Bottom two were salvaged from a previous project, and repurposed for testing the connection to the Feedback Module.
Top two are a variation of the bottom pair.
Test rig to test correct operation of the Hall Sensor.
Further testing with the Servo Tester Modified, correct operation, per activation of the Hall Sensor.
The circuit is fairly simple, consisting of the A3144 Hall Sensor, 10 K Ω resistor to ensure correct operation of the Hall Sensor, and a bridge rectifier to convert the DCC Signal to a rectified DC voltage, approx 21 volts, (figure derived from available voltage provided by the Massoth 1210Z DCC System), and below the maximum voltage for the Hall Sensor.
In operation on the Test Layout, Massoth Automatic Switch routines activated, two Hall Sensor units connected to the 1A and 2A (Orange Wire) on the Feedback Module, Black GND to GND.
White & Brown DCC Track in to bridge rectifier.
LGB Switch decoder, Address 28, connected to a Relay.
Hall Sensor activated on 1A, sends request to the LGB Switch decoder on Address 28, turn Relay ON.
Hall Sensor activated on 2A, sends request to the LGB Switch decoder on Address 28, turn Relay OFF
Further testing, and some form of protective cover to either 3D print, or encapsulate in Resin, for durability for an outside environment.
3D printed housing, purely functional, testing to find optimum for reliable operation.
For outdoor use, covering in Spray on Liquid Electrical Tape over the PCB and components, 3D printed parts to be sprayed will Filler Primer then a top coat black paint.
