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lamaPLC project: Arduino - Vibration sensors
A vibration sensor is a device that detects mechanical oscillations and transforms them into electrical signals to measure displacement, velocity, or acceleration. They are vital for predictive maintenance, enabling teams to identify machine issues such as misalignment or bearing wear before a failure becomes catastrophic.
Common Types of Vibration Sensors
Selecting a sensor depends on the frequency range and whether your measurement target is displacement (position), velocity (speed), or acceleration.
| Sensor Type | Best For | Typical Use Case | Key Benefit |
|---|---|---|---|
| Piezoelectric | High frequencies (>1 kHz) | Bearing monitoring, gearboxes, turbines | Extremely robust, wide frequency range |
| MEMS (Capacitive) | Low frequencies (0–1 kHz) | Imbalance, misalignment, looseness | Low cost, low power, long battery life |
| Eddy-Current | Shaft displacement | Non-contact monitoring of rotating shafts | Measures distance without physical contact |
| Velocity (Electrodynamic) | Machinery protection | Heavy industrial machines, pumps, fans | Self-powered and less prone to overload |
| Laser Displacement | Delicate/Hot surfaces | Precision measurement in clean or harsh environments | High precision, non-contact measurement |
Key Applications
- Industrial Health Monitoring: Used on pumps, motors, and fans to detect early signs of wear and prevent downtime.
- Structural Safety: Installed on bridges, dams, and buildings to monitor seismic performance and structural health.
- Security & Alarms: Detects forced entry on doors or windows (e.g., car alarms or smart home sensors).
- Quality Control: Automotive and aerospace companies test finished products against vibration tolerance benchmarks
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LDTM-028K
The LDTM-028K is a piezoelectric film vibration sensor.
It specifically features a cantilever beam design with an integrated mass (the “M” in the name) to increase its sensitivity, especially at lower frequencies.
Key Characteristics
- Technology: It employs a flexible PVDF (Polyvinylidene Fluoride) polymer film that is 28 μm thick.
- Operating Principle: When the film is bent or vibrates, it produces a high voltage output proportional to the amount of strain.
- Dual Function:
- Vibration Sensor: Functions as an accelerometer when its contacts support it, and it is free to vibrate.
- Flexible Switch: Functions as a switch that produces sufficient voltage to directly activate MOSFET or CMOS circuits when pressed by direct contact.
- Key Benefit: The additional mass decreases the resonant frequency, increasing sensitivity to low-frequency movements and strong shocks.
Technical Specifications
- Sensitivity: Approximately (200 mV/g at resonance).
- Frequency Range: Typically 0.1 Hz to 180 Hz.
- Temperature Range: 0°C to 85°C.
Wiring the Standalone Sensor (Raw Element)
The standalone LDTM-028K features only two crimped contacts. Since piezoelectric elements can produce very high voltage spikes (AC), they need a dedicated circuit to protect your microcontroller and ensure the signal remains stable.
Parallel Resistor: Attach a 1 MΩ resistor across the sensor's two pins. It functions as a pull-down resistor, helping to dissipate static charge.
Microcontroller Connection
- Connect one pin to GND.
- Connect the other pin to an Analogue Input pin (e.g., A0).
Protection (optional but recommended): To prevent voltage spikes from damaging the pins, some designers install a Schottky diode or a Zener diode across the terminals to clamp the voltage to the supply level.
Wiring
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