50PCS 27mm Drum Piezo Elements Sounder Sensor Trigger Disc Copper

KOEED · Electronic Components · Piezo & Acoustic · In stock

What Are the 50PCS 27mm Drum Piezo Elements?

This is a 50-piece bulk pack of 27mm diameter drum-type piezoelectric elements — thin brass (or copper-alloy) discs with a bonded ceramic piezoelectric layer on one face. When an AC voltage is applied across the disc, the piezo ceramic expands and contracts at the driving frequency, causing the entire disc to flex and produce sound. In reverse, mechanical vibration or pressure applied to the disc generates a proportional voltage — making the same component usable as a vibration sensor, contact microphone, knock detector, or acoustic pickup. Each disc has two electrical connection points: one on the ceramic surface (typically the positive/signal electrode) and one on the brass substrate (ground).

In short: These 27mm piezo discs are the standard building block for DIY buzzers, electronic sounders, vibration alarms, knock sensors, and simple acoustic pickups — 50 pieces gives you enough inventory for prototyping, small-batch production, or student lab kits.

How These Piezo Discs Work and Why They Are Useful

1. Bidirectional Electromechanical Transduction

What it means: A piezo disc converts electrical energy into mechanical vibration (actuator/sounder mode) and mechanical vibration into electrical voltage (sensor/generator mode) — it is a true transducer, not just a speaker or just a sensor.
Why it matters: This dual functionality means you can use a single component type for two completely different roles in the same product platform — a buzzer on one PCB, a knock sensor on another — reducing BOM part count and simplifying procurement.
Result: One purchased component serves your acoustic output and vibration-sensing needs, with predictable electrical behavior in both directions.

2. Resonant Frequency Simplicity

What it means: A bare 27mm drum piezo disc has a natural resonant frequency — typically in the 2-8 kHz range depending on brass thickness and ceramic diameter — where it produces the loudest sound output for a given drive voltage.
Why it matters: Unlike a voice-coil speaker that requires a crossover network and enclosure tuning, a piezo disc driven at its resonant frequency produces a piercing single-tone output directly, ideal for alarm sounders, beepers, and attention-getting indicators.
Result: Simple, low-component-count tone generation for products that need to be heard — fire alarm panels, microwave oven completion beeps, truck reverse alarms, and industrial control panel audible alerts.

3. Wide Operating Temperature and Long Life

What it means: The PZT (lead zirconate titanate) ceramic used in these discs maintains its piezoelectric properties across a broad temperature span — typically -20 degrees C to +80 degrees C — and does not require the Curie-point repolarization maintenance that some magnetic transducers need.
Why it matters: Compared to an electromagnetic buzzer coil, a piezo disc has no moving armature, no contact points to arc or wear, and no voice coil that can overheat. The only wear mechanism is mechanical fatigue of the brass substrate if driven far beyond its rated flexural limit.
Result: Decades of operational life in a properly designed circuit — useful for products that are installed once and expected to work for 15-20 years without field service.

Key Specifications

Resonant frequency, impedance at resonance, and capacitance values vary between production batches. Electrical test data for the specific batch may be available — inquire at Moritta@KOEED.COM. Soldering temperature should not exceed 300 degrees C for more than 3 seconds to avoid depolarizing the ceramic.

What You Can Build With These Discs

• Audible Alarm Sounders: Drive the disc at its resonant frequency with a square-wave oscillator (555 timer, MCU GPIO with transistor buffer) for piercing single-tone alerts in security panels, smoke detectors, and industrial warning indicators
• Contact Microphones / Acoustic Pickups: Bond the brass face to a surface (guitar body, machine housing, glass pane) and buffer the piezo voltage with a high-impedance JFET or op-amp front-end for vibration monitoring or acoustic recording
• Knock / Vibration Sensors: Mount the disc flat against an engine block, pump housing, or gearbox casing to detect abnormal impact patterns — the piezo output voltage is proportional to the vibration amplitude
• Ultrasonic Transducers (driver): At diameters around 27mm with appropriate ceramic thickness, some discs can be driven at their overtone frequencies into the 20-40 kHz range for basic ultrasonic distance measurement or cleaning applications
• Energy Harvesting Prototypes: Research projects and proof-of-concept demonstrations that convert ambient mechanical vibration into microwatts of electrical power for low-duty-cycle wireless sensor nodes
• Electronic Drum Triggers: Mounted under a drum head, the piezo disc generates a sharp voltage spike on each stick impact, which a microcontroller reads as a MIDI trigger event — common in DIY electronic drum kits
• Educational Lab Kits: The classic introduction to piezoelectricity — students build a simple buzzer circuit, measure the frequency response, and observe the voltage generated by tapping the disc

Frequently Asked Questions

"Do these discs come with wires pre-soldered, or do I have to solder them myself?"

These piezo elements ship as bare discs with no pre-attached leads. You will need to solder a wire to the ceramic electrode (use a low-temperature iron, less than 300 degrees C, for under 3 seconds) and a wire to the brass substrate. The brass side takes solder readily; the ceramic side requires careful technique — a small solder pad is usually visible. If you need piezo elements with pre-soldered wire leads, contact us for alternative options.

"How loud are these 27mm discs compared to a magnetic buzzer?"

At resonance and with a proper drive circuit (typically 10-30V peak-to-peak square wave), a 27mm piezo disc can produce sound pressure levels of 85-95 dB at 10 cm. A magnetic buzzer of comparable size may reach similar dB levels but draws considerably more current (piezos are voltage-driven, not current-driven — they consume milliwatts at resonance). The trade-off is that piezo discs produce a narrow-band single-tone output, whereas a magnetic buzzer can handle a wider frequency range. For an alarm that just needs to be loud and attention-getting, the piezo disc is usually the lighter, lower-power choice.

"I am building a knock sensor for an engine test stand — will these survive the vibration?"

The brass/copper substrate is mechanically robust within its flexural limits. For engine bay mounting, you should bond the disc to a rigid metal housing (epoxy or cyanoacrylate adhesive) and provide strain relief on the solder connections. The ceramic layer is brittle — it will crack if the brass disc is bent or if a point load is applied directly to the ceramic face. Used within its elastic deformation range with proper mounting, a 27mm disc has been used successfully in DIY engine knock detection circuits. For production-grade automotive sensors, refer to purpose-built piezo knock sensors with integrated housings and connectors.

"What is the capacitance of each disc — I need to design a matching preamplifier?"

A 27mm piezo disc typically exhibits a capacitance in the range of 10-30 nF. However, capacitance varies with ceramic thickness, disc diameter, and manufacturing tolerances. When designing a buffer preamplifier for sensor-mode operation, assume a source capacitance of ~20 nF and select a JFET or op-amp input stage with an input impedance above 1 megaohm to avoid low-frequency roll-off below 20 Hz. For the most accurate design, measure the actual capacitance of a sample disc from your batch with an LCR meter before finalizing your circuit values.

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