The keypads are set of buttons, which usually bears digits, symbols and letters of the alphabets that are arranged in blocks. It can be used as numeric keys, function keys, or both. It is made of mechanical and electrical contact-based system. Most systems of keypad are prone to breaking due to the moving parts and dependence on electrical contact. This system uses a 16-button inductive keypad using a 16-bit MCU. The Inductive sensing is capable of handling rugged and wet environment. It is also has low cost maintenance compared to other system in rugged and wet environment, and scalable keyboard.





The system consist of a keypad assembly, MCU, two 4:1 analog multiplexers, and an inductive to digital converter. The system is supplied by a 5V USB power. A low dropout linear regulator is used to step down the 5V USB power to the 3.3V required by the LDC1314 inductive to digital converter and MSP430 MCU. The LDC1314 is a 4-channel inductance to digital converter that is set to a continuous conversion mode. The design can be expanded to 32 or 64 keys by using the rest of the channels. The MCU is used as a bridge between the LDC1314 and the USB port. It also provides the non-volatile memory for the dial’s calibration data. The sensor design has a diameter of each coil of 8mm, matching the size of its snap dome. It has a nominal inductance of the coil of around 2.3uH. Each coil contains 16 turns on each side.





The induction sensing keypad can work in harsh, rugged and wet environment, it is suited in applications like point of sales terminals, gas station pump keypads, vending machines, ATM, industrial equipment, health maintenance devices, building automation and access control equipment.