Findings, Analysis and Challenges
This section discusses the key observations, analysis and issues faced during the implementation of this POC.
Observation 1: The Piezoelectric Sensor produces a higher voltage when it is bent or on a hollow surface. Thus, have placed the sensor on the bottle cap. In order to conclude that the sensor produces a higher voltage when placed on a bottle cap, the sensor was first placed on a flat surface and then a sponge followed by a slightly elevated bottle cap. Then, the voltages produced were compared. It was then concluded that the bottle cap produced a voltage of up to 7.5 V compared to 3-4 V on the other surfaces.
Observation 2: The Piezoelectric sensors produce a higher voltage when placed in close proximity to each other.
Observation 3: The Piezoelectric sensors work better when all the sensors are being knocked at once together.
Observation 4: 4 Piezoelectric sensors are able to light up 3 12V DC LEDs!
Analysis
According to the direct piezoelectric effect, the following are characteristics of electric charge Q:
Q∝d
Q∝S
Where:
Q is the electric charge generated by the piezoelectric sensor
d is the piezoelectric coefficient (a material-specific constant)
S is the applied mechanical stress or deformation
The electric charge generated by the piezoelectric sensor is directly proportional to the applied mechanical stress or deformation. The voltage (V) can be obtained by dividing the electric charge (Q) by the capacitance (C) of the sensor:
V=Q/C
Where:
V is the voltage generated by the piezoelectric sensor
Q is the electric charge generated by the piezoelectric sensor
C is the capacitance of the piezoelectric sensor
Therefore, the higher the piezoelectric coefficient d, the higher would the voltage be. And the higher the applied mechanical stress s, the higher the voltage.
Assume in this POC, that the coefficient d is constant since identical piezoelectric sensors have been used.
On a flat surface or a sponge, the mechanical stress experienced by the piezoelectric sensor is relatively uniform, leading to a certain level of voltage output. However, when the sensor is placed on a hollow surface like a bottle cap, the curvature and the specific shape of the surface cause localized areas of higher mechanical stress. This non-uniform stress distribution increases the separation of charges and leads to a higher electric field and voltage output, as observed.
When multiple piezoelectric sensors are placed in close proximity to each other, their individual responses can influence each other. This phenomenon is known as the coupled effect or the cooperative effect.
The close proximity of the sensors allows for the transfer of mechanical stress or vibrations from one sensor to the others. As a result, the total mechanical stress experienced by each sensor is enhanced, leading to an increased generation of voltage. This cooperative effect can amplify the voltage output compared to the voltage produced by individual sensors when isolated.
Lastly, when all the piezoelectric sensors are knocked at once together, they experience a synchronized mechanical stress or deformation. This collective impact creates a higher overall mechanical stress on each sensor compared to when they are knocked individually or at different times, resulting in higher voltage output from the sensors.
Challenges
No major challenges or issues were faced during the implementation of this POC.
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