Keyclick flute5/1/2023 This prevents changes of the impedance at the MCU input pin, as well as a limited amount of ESD protection.īy substituting the voltage divider resistors with two equivalent resistances (RE1 for the upper set of resistors, and RE2 for the lower set of resistors) the principle can be understood even better: when the top button is pressed (T1), the equivalent RE1 resistance will be 0 Ω, so regardless of the RE2 resistance, the voltage at the AN pin will be equal to VCC. The buttons are rubberized and have a pleasant tactile feel when pressed.īy pressing a button, the respective connection point becomes redirected to the input of the OPA344, a low-power operational amplifier from Texas Instruments, which is configured to work with the unity gain, forming a buffer for the input of the microcontroller (MCU). These buttons are rated to endure up to 300,000 switching cycles and have very low ON resistance of less than 100 mΩ. The KMR2 series KMR221 tactile buttons are high-quality SPST switches produced by CKSwitches, a company specialized in production of various types of quality switches. Those resistors are connected in series, and each connection point is routed to one pin of the SPST pushbutton. How does it work?Īs already mentioned, the working principle of this Click board™ is very simple: it contains a voltage divider, formed by six 1 kΩ resistors. This type of keyboard can be used as password terminals for small alarm systems, for selecting an option in various embedded applications, and for all kinds of small DIY projects where low pin count is a big concern. Featuring six high-quality pushbuttons, a simple debouncing circuit, and the output op-amp buffer, this Click board™ is an ideal solution for different applications controlled by discrete voltage levels, but also for applications which have restricted number of free pins.
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