Simple 555 Timer Circuits & Projects - Electronics Hub LC Meter Circuit using 555 Timer: The LC meter circuit shown here will measure the value of a reactive element like capacitor or an inductor. This circuit is designed using 555 timer IC. Frequency Counter Circuit: This project shows a frequency measuring circuit. The two 555 555 Timer IC: Internal Structure, Working, Pin Diagram and Jun 18, 2015555 Timer IC is one of the commonly used IC among students and hobbyists. There are a lot of applications of this IC, mostly used as vibrators like, ASTABLE MULTIVIBRATOR, MONOSTABLE MULTIVIBRATOR, and BISTABLE MULTIVIBRATOR.