This circuit of “Dynamic Display Ads” is based on serial input and parallel output sift register 74164. With the help of the circuit dynamic display ads we can build a display board, where LEDs blink to give a running light effect.
The circuit dynamic display ads may be used to advertise or display of name plates etc. It is made versatile by using the 555 and 74 series of ICs, which are readily available in the market.
In the circuit dynamic display ads we have given four inputs to IC 74164 and Vcc supply of 5V is given at pin 14. The output here is taken from pins 3, 4, 5, 6, 10, 11, 12 and 13. The input to the pins 1, 8 and 9 are given with adjustable frequency. The input given by IC 555 is designed for 50%duty cycle, with T = 2Ã—7.92 ms. Pin 2 in IC 74164 (IC3) is made ‘high’ continuously to enable input. Pin 8 of IC3 takes clock pulse from timer IC2 having 50% duty cycle with time period of 0.555 sec. the output from pin 13 of IC3is inverted by IC4 and given to pin 9 of IC3. This terminal is used for resetting purpose. In IC 74164 the data of pin 3 shifts to pins 4, 5, 6, 10, 11, 12 and 13 successively. We have used LEDs at output terminals of IC3 which act as load. The LEDs are arranged in such a way that they form a display. As the LEDs connected to pin 13 glow the whole display will reset and the cycle will start again.
Here we have the display of LEDs arranged in a way to make ‘ELECTRON’ with the output pins 3, 4, 5, 6, 10, 11, 12 and 13 respectively. In the first cycle the letter E will glow, in the second cycle L will glow, in the third cycle the first and the third letter will glow. In the fourth cycle C and L will glow, in the fifth cycle E, E and T will glow, in the 6th cycle L, C and R will glow, in 7th cycle E, E, T and O will glow and in 8th cycle L, C, R and N will glow and the circuit will be reset switching off the whole display. After receiving the reset pulse, the first cycle will start again and will display in the same manner. The above operation will be so fast it will give a running light effect. This is limited up to 7 characters only.
We can increase the display by 7 characters by cascading one more IC 74164. If we are cascading four ICs, we can get 7+4*8=39 characters. Here we can cascade as many ICs as we require. For cascading purpose, the output of pin 13 of first IC 74164 should be given to the input of second IC 74174 at pin 1. And the reset input pin 1 should be connected to the same as corresponding pins of first IC 74164. In place of LEDs we can also display of AC bulbs. For this purpose we have to use relays at output terminals and this relay should be of high switching speed.
The waveform is shown in figure 2.
NOTE: Time period of IC1 applied at A input of IC3 is doubled the CLK input 8, i.e. A input period = 1.10 sec. approximately.
PARTS LIST OF DYNAMIC DISPLAY ADS.
Resistor (all ¼-watt, ± 5% Carbon)
R1, R2 = 72 KΩ
R3, R4 = 36 KΩ
C1 – C4 = 10 µF/10V
IC1, IC2 = NE555
IC3 = 74164
IC4 = 7404
D1, D2 = 1N4148