Timer IC 555 is a free Android app developed by sweet_baked_pie that helps calculate the values of resistors/capacitor from frequency and duty cycle, and vice versa. The app is based on the industrial standard timer IC 555 and is a useful tool for professionals and hobbyists alike.

One of the standout features of Timer IC 555 is its ability to limit the values of resistors/capacitor to E3/E6/E12/E24 series, providing greater accuracy and convenience. Additionally, the app provides a simple waveform output and supports only Astable operation.

To use the app, there are two methods. The first method involves inputting the values of resistor Ra, Rb, and capacitor C, after which the app outputs the frequency, duty cycle, and waveform. The second method involves inputting the frequency and duty cycle, and the app outputs a list of recommended parts (resistor Ra, Rb, and capacitor C) that can be used as input for the first method.

Overall, Timer IC 555 is a well-designed and practical app for anyone working with the 555 timer IC.