Features and Specifications for 16 Key Proximity Keypad,

The QKEYPAD is a 16 key proximity keypad intended to detect human touch through any dielectric panel up to a thickness of 10 mm. This product is designed specifically for OEM users needing to provide data entry into a sealed or protected environment.

The Qkeypad features:

·	16 touch keys through any dielectric up to 10 mm thick.

·	4 x 4 Analog crosspoint switch output to mimic traditional electromechanical keypads.

·	TTL Uart port.

·	User selectable sensitivity ranges via DIP switches.

·	Key active LED indicator.

·	Auto calibrating with noise and adjacent key suppression.

·	100% surface mount components to ensure easy mounting against any flat panel.

·	Access to power and signals via industry standard DB15 connector.

When placed behind a panel made from any dielectric material such as glass, wood, or plastic the contacting surface becomes a touch sensitive keypad with 16 discrete keys. During operation minute amounts of charge is coupled by a set of 16 electrodes through the overlying panel. Any contact with the panel over the area of the electrodes causes charge
to leak away from the electrodes and a corresponding drop in voltage is detected as a key activation.

Interface Selection
The interface is selectable between a 4x4 analog crosspoint matrix, and a uart output. Selection is made by way of a switch on the DIP switch array.
Shown here is the equivalent circuit output when the analog crosspoint matrix is selected. The row to column connections for inactive keys are effectively open circuit. When a key is selected the row to column connection remains active until the key is released. When selected the uart output will transmit key codes whenever the corresponding key is activated. Codes are sent once at the point of contact detection

The Qkeypad proximity keypad unit has 16 proximity key sensing areas. The sensing areas consist of simple PCB tracks of conducting material that when pulsed with an electric charge creates an electrostatic field surrounding each proximity key area. When a non-conductive panel is placed over the Qkeypad the electrostatic field permeates through the panel above the sensing area. When contact is made by the human finger some of the charge flowing through the overlying panel is "leaked" away as shown in this figure below.

This leaking away of charge is detected by the associated circuitry as a change in voltage levels. When the change in voltage beyond a certain reference level reaches a defined trigger point the Qkeypad detects this as a key press.

In practice any object near the sensing electrodes will cause some leaking of charge to occur. Also water droplets and other surface contaminates will cause coupling of the electrostatic field between the individual proximity keys. To avoid a false trigger an individual reference voltage is generated for each proximity key area. Additionally the reference voltage is adjusted periodically to allow for any fluctuating influences such as water moisture that would change with time at a rate much slower than would be the case for a genuine key press

Applications:

·	Interactive Shop Windows - Estate Agents - Electrical Goods Demonstrators

·	After Hours Viewing - Information Points - ATM Machines

·	Appliance Controls - Security Keypads - Vandal Proof Keypads

·	Ultra Rugged Control Panels - Heating Controls - Lighting Controls

·	Exterior Keypads - Exhibition Stand Interface - Hidden Controllers - Touch Systems