E-Field Level Sensor Based on MC33794

The system of MC33794-based E-field sensor was designed around the MC68HC908JK3 microcontroller to be used in any plastic containers in order to detect the liquid levels.

The project is utilizing the MC33794 for detecting objects in an electric field where an electrode is associated. This is used for applications where non-contact sensing objects are preferred since a low-level electric field is generated by having the necessary circuitry while the field loading caused by objects moved into the field is measured. By using an external resistor that has been optimized for 125 kHz, the frequency becomes adjustable and a low-frequency sine wave is generated by the IC. The generation of harmonic interference will be avoided since the sine wave has a very low harmonic content. A nominal 5V peak-to-peak output is produced by the internal generator that is included in this E-field sensor.

The aluminum foils are used to make the electrodes and are wrapped all around the circumference of the container. Due to the size of the container used in the prototype and width of aluminum sensor rings, 6 of the 9 channels available in the MC33794 are used by the system.
Read more