This post is part of the series IC 555 Tested Mini Projects
Other posts in this series:
This is a very interesting circuit of IC 555 Head or Tail Project. It uses a simple trick that if we break the charging path of the timing capacitor in AMV circuit using IC 555, then the output condition of the circuit remains locked in a particular state.
First note that the circuit uses PUSH TO OFF type switch shown on the left side of the circuit. When this switch is NOT PRESSED, then its contact is made and when it is PRESSED its contact is broken. Such type of switch is used in car door light and refrigerator door light.
Now when power supply is connected to the circuit, keeping the Head/Tail Sw in released condition, the capacitor C1 starts charging through resistors R1 and R2. So the output of the IC changes from HIGH to LOW and LOW to HIGH at a very fast rate, because the R1, R2 and C1 have very small values.
The two LEDs – red and green are connected in series and their middle point is connected to output pin-3 of the IC. So when the output of the IC changes to HIGH, the lower green LED D2 glows, and when its output is LOW, the upper red LED glows.
Now when the Head/Tail switch is pressed at random, either during charging or discharging phase of the capacitor C1, then the RED or GREEN LED stays ON at random.
You can check the actual working of this circuit, in following video also.
Note that, the time for which you press the Head/Tail switch, the output condition of the circuit remains stable i.e. either Head or Tail. The moment you release this switch, the output of the IC starts changing again at a fast rate.
You can select the values of R2 and C1 as per your requirement. The values given here are practically tested values. This project is suitable for mini project submission at your school or college. The PCB layout of the circuit is also given below.
The practically tested PCB layout of the above circuit is given below. The following image is NOT size proportional. If you want to get the PCB layout of this circuit for actual construction, then contact us. We shall send you the actual size PCB layout for free.
Video of actual working
Continue reading this series:
IC 555 simple burglar alarm mini project