Free running loop pendulum for time clock algorithm

Abstract

Time based control loop in digital algorithm could be accomplished through built-in circuits such as watchdog timer or external device that known as Real Time Clock (RTC). Another option which is simple, fast and easily implemented is by using free run internal coding interval. The accuracy is not as good as compared to RTC but it simplifies a lot of work especially setting up time during interfacing hardware between microcontroller and RTC. Those who experience with the intermittent work with RTC, escaping the choice with something else is always triggered in mind. RTC is good but the process of activating the device must be properly done through hardware and software. Hence this problem initiates a very simple technique that could be used to replace RTC by using free run internal coding. Microcontrollers need 4 clock cycles to execute one line of assembly code. In a simple free control loop for instance 100 assembly codes, it will consume 5 us to complete the execution in 8 MHz oscillator. As long as the time taken to complete a loop is less than a second, the free run loop coding is executed to function as pendulum in mechanical clock. The result from this work shows very marginable run time error and the most important issue is simplicity of constructing the time base circuit gives a very good option.