Keypads Buying Advice
A keypad is a set of buttons arranged in a plastic or metal block which usually bear digits and other symbols but not a complete set of alphabetical letters. If it mostly contains numbers then it can also be called a numeric keypad. Others like fingerprint sensor and optical sensors.
Most keypads allow users to press keys or enter codes to control equipment, machinery and for household usages. People can set one person or multiple people to access to the keypads. Keypads use several basic switching technologies. Direct membrane keypads include a membrane painted with conductive ink, a spacer, and a substrate. Holes punched in the spacer are arranged so that pressing a key deflects the contacts on the membrane to complete the circuit on the substrate. Indirect full-travel membrane keypads
mount keys above three layers of punched, flexible polymer sheets that are sandwiched together. Circuits are silk-screened with a conductive silver ink on both the top and bottom membrane layers. A middle spacer separates the two circuits and holes punched in the top spacer are arranged so that pressing a key deflects the top circuit to connect with the bottom circuit. Carbon pill keypads contain protruding, pill-shaped covers that are molded over the top of each key. When a key is pressed, the conductive
pill actuates a pad trace. The average life for a carbon pill exceeds 5 million actuations. The contact resistance is usually less than 200 W. Usually all keypads are programmable, 4-8 digits of codes could be preset. Each keypad could have over 100 million combinations of codes to set. Standard keypads mount on the front or rear of panels and are made from a variety of plastic, thermoplastic, and metallic materials. There are four standard keypad sizes: 1 x 4, 3 x 4, 4 x 4 and 5 x 4. For each keypad size,
the first number indicates the number of columns and the second indicates the number of buttons. For example, 1 x 4 keypads have one column and four rows of buttons. 3 x 4 keypads are telephone-style devices with three columns and four rows of buttons. 4 x 4 keypads have four columns and four by rows of buttons. 5 x 4 keypads have five columns and four rows of buttons. Electrical switch specifications for standard keypads include maximum current rating, maximum alternating current (AC) voltage rating, and
maximum direct current (DC) current rating. Standard keypads with X-Y outputs are matrix-style devices. Devices with a single pole or common bus outputs require the same number of pins as buttons. Standard keypads are often backlit and include light emitting diodes (LED) to indicate process status, system functions, machine interlocks, and alarm conditions. Embossed switches have graphics or alphanumerical characters that are raised from switch surface. Switches, panels and keypads that are designed for outdoor
use are water resistant or waterproof and can withstand both ultraviolet (UV) light and variations in temperature. Standard keypads that are used in medical and electronics applications provide protection from electromagnetic interference (EMI), radio frequency interference (RFI), and electrostatic discharge (ESD). ESD protection may be accomplished with static-dissipative or conductive elements in the switch material, or through special electronics grounding.
Buying suggestions
Pay attention to the material used for the keypad you selected. Some of the touch screen keypads make sure there is not defection on the LCD screen. Keep the receipt well and leave your exact address and phone number for convenience of free installation. Also, test for the code setup process and check how it works and make sure it can be easily operated.
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