Simple Head and Tail
Several complicated electronic head or tail circuits have already been published in www.electronicsproject.org. But this is a very simple circuit which uses a CMOS CD4017 counter IC.
This circuit is operated by touching the plate. This action injects AC mains hum to the input pin 14 of IC. The outputs Q0 to Q5 from this IC are used to drive the two LEDs. It is very difficult to predict which LED will remain illuminated.
To make the circuit more attractive, it can be modified to display a letter ‘h’ or‘t’ on the 7-segment common cathode LED display.
As e, f and g segments of the diplay are hard wired to the positive of the supply, high value resistors are used to maintain same intensity of all the segments.
The circuit has been excellently simplified and superbly designed. I would like to further simplify it by modifying, thus eliminate the need for six diodes.
The further modification in above circuit is shown below.
Resistors (all ¼-watt, ± 5% Carbon)
(For figure 1)
R1 = 10 MΩ
IC1 = CD4017
D1 – D6 = 1N4148
LED1 – LED2 = Two different LEDs