Circuit knowledge

This is a Simple 555 Tester Circuit Diagram. The IC 555 is a widely used timers, control diagram, PWM, alarms, etc.. Often we set up a schema that does not work or works differently than expected, this time the ideal is a test schema for this IC. 

This test schema 555 is connected as an astable multivibrator when the button switch S1 is pressed, the LEDs D1 and D2 flash alternately. Ie, when the output is high D2 will light when the output is low D3 will light, and the other a Hi Lo. The speed of flashes is determined by the components R1, R2 and C1.Pressing the S1 test the 555 starts and any change in the IC flashes may consider to be defective.