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Aquaponics

final sensor design

The Aquaponics project goal is to find a way to measure the electric field of a plant. The team worked on designing a set of probes with electrodes that can measure the electric field emitted by a plant. The idea is to design two probes with electrodes that can catch the electric potential from the atmosphere around the plant and the plant itself.

final sensor design
Final sensor design front side (left) and back side (right).

Project description

Our approach is to measure the potential in the air and close to the plant, followed by digital filtering to reduce the noise in the measurement results. We compare our measurement results a COMSOL simulation of the process. If the physical measurements align with the simulation, then we have a higher confidence that the results can be trusted.
Each time we will do two measurements: one without the plant in between the probes and one with the plant in between the probes. With these measurement results, and knowing the distance between the electrodes and probes, the electric field caused by the plant can be calculated.
Digital filtering to eliminate noise is important because the value of the electric field of the plant is very low, in the range of millivolts per meter (mV/m), and the signal has an extremely low frequency (zero or close to zero).

Project results

From the simulations it is clear that a plant can be easily detected and mapped with enough electrodes on the probe. However, to map the shape of the plant accurately, additional software has to be developed. It is very challenging to determine the dielectric constant of the plant from the measurements. The dielectric constant is required to be able to draw conclusions about the water content and substances present in the plant, which is the ultimate goal. The dielectric constant’s effect on the voltage differential across the electrodes is expected to be 35 mV at maximum. This is in the range for reasonable dielectric values for the plant and can be determined by a high precision measurement.

The sensor that we designed is a good fit for the project goal. The follower circuit that was implemented on a breadboard works according to the expectation, but for a better stability we advise to create a dedicated PCB for it. The performance of the probes system meets all the requirements defined at the beginning of the project.

Video

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