|
Automatic
Dual-output Display
|
| This
circuit lights up ten bulbs sequentially, first in one
direc- tion and then in the opposite direction, thus presenting
a nice visual effect. In this circuit, gates N1 and N2
form an oscillator. The output of this oscillator is used
as a clock for BCD up/down counter CD4510 (IC2). Depending
on the logic state at its pin 10, the counter counts up
or down. During count up operation, pin 7 of IC2 outputs
an active low pulse on reaching the ninth count. Similarly,
during count-down operation, you again get a low-going
pulse at pin 7. This terminal count output from pin 7,
after inversion by gate N3, is connected to clock pin
14 of decade counter IC3 (CD4017) which is configured
here as a toggle flip-flop by returning its Q2 output
at pin 4 to reset pin 15. Thus output at pin 3 of IC3
goes to logic 1 and logic 0 state alternately at each
terminal count of IC2. Initially, pin 3 (Q0) of IC3 is
high and the counter is in count-up state. On reaching
ninth count, pin 3 of IC3 goes low and as a result IC2
starts counting down. When the counter reaches 0 count,
Q2 output of IC3 momentarily goes high to reset it, thus
taking pin 3 to logic 1 state, and the cycle repeats.
The BCD output of IC2 is connected to 1-of-10 decoder
CD4028 (IC4). During count-up operation of IC2, the outputs
of IC4 go logic high sequentially from Q0 to Q9 and thus
trigger the triacs and lighting bulbs 1 through 10, one
after the other. Thereafter, during count-down operation
of IC2, the bulbs light in the reverse order, presenting
a wonderful visual effect. |
|
|
Click on the Image for it larger version
|
