QuickPack - Technical Notes

Tech notes - 4

Integrating the Quickpack OmniCom Transducer Into a Handheld Product

The Midé OmniCom transducer is a member of the QuickPack actuator family of products. It is a packaged, piezoceramic device that is operated as a bimorph actuator to provide tone alert, vibration alert and speaker functions. By combining 3 features into a single compact device, manufacturers of handheld devices can add functionality, and reduce the size and complexity of their products.

Operating the OmniCom transducer requires clamping the ”tail end” of the transducer and attaching this clamp to the housing of your product. By applying a voltage to the clamped transducer, you will actuate the tip of the device which will produce an audible or vibratory output. (See Figure 2.) Supplying varying frequency and voltage inputs changes the mode of operation: tone, speaker, vibration.

There are a variety of methods for integrating the OmniCom transducer into an OEM product. This note outlines a reliable integration method for the OmniCom transducer. It is the method used to fabricate the OmniCom demonstration unit. Midé can work with OEM manufacturers to design and implement alternative methods.

1. Select Location

The OmniCom transducer requires a 0.67” × 1.83” area. During operation the maximum displacement at the tip is 0.17” (since there is no deflection at the clamp end, other handheld product components may be located nearer to the transducer). The OmniCom transducer resonates the OEM product housing itself, so it should be placed in a location which provides a suitable case panel radiating surface of at least 1.40” × 2.25”. While this panel area may house other device components, the panel itself should be free of stiffening ribs. The wall thickness of this panel area should be 0.060”. (For demonstration and evaluation purposes, an existing housing may be modified by milling to the specified thickness and removing any ribs etc.). Ideally, the actuator should be clamped near one edge of the panel, on axis with the center line of the panel surface. This allows the transducer to resonate a larger panel area without being constrained by the stiffness of the product walls or other stiffeners. (See Figure 3.)

The OmniCom device operates without any special enclosure or speaker grille and does not require the OEM product housing to be sealed.

2. Clamp Device

A firm clamp is required to achieve the optimal performance. The OmniCom demonstration units use a 6061-T6 aluminum or 303 stainless steel clamp. Other materials like ceramic or plastics may be used. When evaluating alternative clamp materials ensure that the clamp does not creep nor deform during operation.

The clamp should be positioned over a 0.6" x 0.2" area of the piezoceramic portion of the transducer. The suggested clamp size is 0.7" x 0.5".(see figure 4) Two #2-56 UNC screws are used to fasten the clamp to the product housing. Tightening screws to apply a 2.5 inlb. torque (280 lbs. total) force provides ideal performance. While tests have shown that varying the clamping pressure may produce satisfactory performance; at the extremes, under-clamping will lead to lower outputs and over-clamping may damage the device. (NOTE: The QuickPack device's protective coating mechanically protects the piezoceramic elements and electrodes against cracking in the clamping region allowing ACX to recommend approximately 2300-3000 PSI for QuickPack bimorphs. This ideal clamping pressure could fracture unprotected, "raw" piezoceramic materials).

Screws / actuator holes provide ideal registration actuator holes provide ideal registration features for high volume manufacturing. Mide can work with OEMs to evaluate alternative clamping options such as insert molding and bonding.

3. Electrical Connection

The OmniCom transducer provides two exposed and knurled brass contact pads. Electrical contact can be made to these pads by leaf springs, pogo pins or conductive elastomers, or wires can be soldered directly to the pads.

4. Driving Conditions

The QuickPack actuators are capacitive devices; the OmniCom transducer has a capacitance of 40nF. Like most piezoceramics, QuickPack OmniCom actuators require high voltage and low current. The electronics subsystem that drives the OmniCom transducer should be capable of delivering 0.5W power, a bandwidth of at least 6.5KHz and should be able to reach peak voltages of ±75V. The Mide 1224/5 QuickPack Power Amplifier can easily meet these needs for lab evaluation. Discrete drive electronics or an ASIC, such as SIPEX model SP4515 , are appropriate for production solutions. Figure 5 illustrates the functionality of the complete system.

Omnicom system architecture.

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For more information:

Please email Conor Clery (Products), or call: 781-306-0609 x292