An iButton is a device with a microchip that is encased in a durable stainless steel enclosure measuring 16 mm thick and meant to resemble a button, hence the name. It is designed to be durable and mountable anywhere so that it can be used to carry up-to-date information, even in harsh outdoor environments. It is very small and portable, and can be attached to a ring, watch, key fob or other personal items to be used as access control for devices, computers and buildings, and then carry out data logging and data management tasks.
The iButton uses its “can” housing as the communications interface with the lid being the data contact and the base (formed by the sides and bottom) acting as the ground, which are all connected to the microchip inside. Both leads are separated by a polypropylene grommet through which a perfect seal is made that prevents dust and water from getting through to the microchip.
Data is read and placed in the iButton using a 1-Wire interface that only requires the user to touch the iButton to a corresponding reader connected to a computer system or any other electronic system designed for the iButton. It essentially has the same applications as smart cards, only the application is much more diverse because of its form-factor — for starters it can be placed on large machinery, shipping containers, outdoor locations or other items and places that are exposed to the elements where a smart card form-factor may fail easily. The application differs depending on the type of chip used for the iButton.
Types of iButtons include:
- Address only – Simple microchips that only contain unique serial numbers used for identification, access control and verification applications
- Memory – May use EEPROM, EPROM or NVRAM chips to store information such as destination and route, lists such as contents of a container or other data
- Real-time clock – Contains a chip that maintains time
- Secure – Contains encrypted data
- Temperature and data loggers – Contains a chip with more memory for saving data from sensor systems quickly