Pulse Motors: Allegro A3503 Hall Effect Sensor Demo
The Allegro Microsystems A3503 Ratiometric Hall effect sensor, combined with a TL082 dual JFET-input op-amp chip, makes a very versatile tool that can be used for many purposes. Schematic at the end of the video.
It can be used as a magnet polarity indicator, a pulse motor driver sensor stage, a current monitor, even an electronic compass.
Here I demonstrate the sensor and op-amp combination in a basic driver configuration, using LEDs as the driven loads. The LEDs could of course be replaced by driver transistors for switching heavier loads, like levitator coils or pulse motors.
With a slightly different wiring of the op-amps, the output could be made proportional instead of “all or none” as with the comparator configuration, and this could make a sensitive gaussmeter or proximity indicator. The Allegro data sheet for the sensor also shows how to use it for a gear-tooth sensor or a current monitor.
The applications of the sensor + op-amp are endless, limited only by the imagination… and the power source.
The sensor needs 4.5 to 6 volts to operate, and I’ve provided a stable voltage source with the 78L05 mini-voltage regulator, which is used both for the sensor power supply and the reference voltages for the two independent comparators, with setpoints independently controlled by the 2 ea. 20-turn 50k trimpots. The chip has a bandwidth of about 24 kHz so it can switch very fast. The op-amp can switch even faster than that.
I used a small transistor socket for the Hall sensor itself since the leads are tiny, and I simply stuck the TL082 chip, upside down, to the board with a piece of double-stick foam mounting tape. I used wire-wrap technology to connect to the upward-sticking pins of the chip and soldered connections elsewhere.