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
- Surge Protectors
- Low Battery Indicators
- Pill Dispensers
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.