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Mounted Transducers

Mounted Transducers

Mallory’s mounted transducer models do not contain circuitry, so the user must apply the correct frequency signal to the device. Mallory offers both piezo and electromagnetic technology. Electromagnetic mounted transducers utilize a metal disc deflected by an electro-magnet inside a plastic housing. These devices can produce relatively good sound levels at a very low voltage in a very compact package, so they excel in electronic applications where space is limited, low DC voltage is available, and only a soft or medium sound level is needed. Piezo mounted transducers consist of a piezoelectric element mounted in a plastic housing. These devices have much lower current draw and can produce extremely loud sound levels, an example being the ear-piercing sound produced by smoke detectors.

There are two basic types of mounted piezo transducers to choose from. Direct drive mounted transducers have just two terminals which make them relatively easy to implement in an application. The user must apply a peak-to-peak sine or square wave signal to the device at the appropriate rated device frequency. Self-drive mounted transducers have three terminals. The third terminal supplies a feed-back voltage which is 180 degrees out-of-phase with the primary frequency signal, so the feedback signal helps the circuit self-tune itself to the optimum sound frequency. The result is a simpler circuit and an optimized sound level. The challenge with a self-drive circuit is that the transducer is becomes an integral part of the circuit, so more time will be spent designing and testing the circuit to make sure it works properly under all application conditions.

Mounted transducer package types include surface mount, PC pins, and flange mount with wires. Because mounted transducer devices do not have circuitry, they will be at a lower cost point than buzzers with circuitry.

Mounted Transducer Applications

  • Bar Code Readers
  • Non-Critical Medical
  • Detectors (Smoke or CO)
  • Key Pad Entry
  • Appliances
  • Surge Protectors
  • Low Battery Indicators
  • ATM’s
  • Tools
  • Pill Dispensers

Transducers-External Drive-Piezo

Piezoelectric external drive transducers come with two terminals or wires that are connected to the piezoelectric element. By applying a sine or square wave to the device at the appropriate drive frequency on the specification sheet, an audible sound at that frequency will be produced. The more peak-to-peak voltage applied (up to the rated maximum), the higher the sound level. Square wave signals will generally produce more sound level than sine wave signals.

Transducers-External Drive-Electromagnetic

Electromagnetic external drive transducers come with two terminals or wires that apply the voltage signal to the sounder element. The operating voltage range of these buzzers is typically limited to a much more narrow range as compared to piezoelectric technology, so applying more peak-to-peak voltage to get more sound level is not helpful with these electromagnetic buzzers.

Transducers-Self Drive-Piezo

Piezoelectric self drive transducers come with three terminals or wires that are connected to the piezoelectric element. The third wire or terminals is connected to a small isolated portion on the piezoelectric transducer which provides a feedback voltage signal which can be fed back into the circuit so that the circuit self-tunes itself to the optimal sound frequency. These devices do require the designer to spend more time optimizing the circuitry so that the buzzer performs optimally under all expected environmental conditions. The advantage of using self-drive piezo transducers is a more simplified (and lower cost) circuit, and a buzzer design that will emit maximum sound level every time.