The Wiegand interface is a wiring standard used to connect a card swiping device to an access control system. As such, you can see it in a typical point-of-sale (PoS) device found in a store, restaurant, hotel, or any establishment that accepts card payments.
The Wiegand interface takes its roots from the popularity gained by the Wiegand effect card readers in the 1980s. The Wiegand effect is a nonlinear magnetic effect named after John R. Wiegand. It is produced in specially heated and hardened wires called “Wiegand wires.”
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Read More about the “Wiegand Interface”
The video below describes what the Wiegand interface is.
How the Wigand Interface Works
A Wiegand interface uses three wires in the physical layer. The first is a ground wire, while the remaining two are for data transmission. The data transmission wires are called “data low/DATA0” and “data high/DATA1.”
The data transmission wires can send three inputs to readers:
- No data: DATA0 and DATA1 are pulled up to a high voltage.
- “0”: The DATA0 wire is pulled to a low voltage, while DATA1 stays at a high voltage.
- “1”: DATA0 stays at a high voltage, while DATA1 is pulled to a low voltage.
In a door keycard, no data requires no response. “0” could translate to keep the door closed, while “1” tells the reader to open the door.
Applications of the Wiegand Interface
The Wiegand interface has several applications explained in more detail below.
Wiegand Sensors
Wiegand sensors are magnetic sensors that power energy-efficient devices. They don’t need an external power source. Instead, they use the Wiegand effect to generate a consistent pulse each time the magnetic field polarity reverses.
Wiegand Keycards
The Wiegand interface is also used for security keycard door locks. Plastic keycards have a series of short lengths of embedded Wiegand wires. The presence or absence of wires in each keycard makes it unique. A second set of wires serves as a clock track. When a card is slid through a reader’s slot, its magnetic state reverses, telling the lock to open.
Rotary Encoders
Some rotary magnetic encoders use Wiegand wires to power multiturn circuitry. As the encoder revolves, the Wiegand wire core coil generates a pulse of electricity sufficient to power it and write the number of turns to nonvolatile memory. This process works at any speed and eliminates the need for a clock or gear mechanism.
Wheel Speed Sensors
Wiegand wires are fitted to wheels to measure rotational speed. An externally mounted reading head detects Wiegand pulses.
Devices That Have a Wiegand Interface
Examples of everyday things with a Wiegand interface include fingerprint readers, card swipers, and iris recognition devices to control door panels.
Advantages and Disadvantage of Using the Wiegand Interface
Using the Wiegand interface has both benefits and drawbacks that include the following:
Advantages
The Wiegand interface is easy to implement and use when sending data between two units. It also works when encryption is not necessary, or only a low level of security is required.
Disadvantages
If the data sent from a card reader is not encrypted or sent in plain text, anyone can read it. The Wiegand protocol is one-way. It doesn’t have card write data functionality.
Data a Wiegand Interface Can Read
The data that Wiegand interfaces can interpret include credit card numbers, bank account numbers, employee identification information, criminal records, and medical histories. This ability makes Wiegand devices useful for stores, restaurants, hotels, companies, banks, law enforcement agencies, hospitals, and many other organizations that use the aforementioned data.
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The simplicity of the Wiegand interface is the primary reason why it’s still in use today.
