IC 555 Based Message Display Circuit

Here is a simple circuit that displays a “HAPPY NEW YEAR” message. The alphanumeric display can be fitted anywhere in your home .This simple message display circuit is built around 555 ICs, twelve KLA511 common-anode alphanumeric displays(IC1 to IC12) and a few discrete components.

IC 555 functions as timer circuit and message is displayed for two minutes which is pre-determined by making the 555 work into monostable multivibrator mode. In this mode, one state of 555 based timer has a fixed duration, while other state surfaces up only when an interrupt is witnessed.

KLA511 displays are a popular category of alphanumeric LED displays that consume low power and can work for longer duration without generating excess amount of heat. Each KLA511 unit comprises of 7 LEDs and has a common-anode circuit arrangement which along with some passive components, gives optimized display outputs.

For easy understanding, the entire circuit can be divided into two sections: controller and display. The controller section is built around IC13 while the display section is built around alphanumeric displays (IC1 to IC12).

As shown in the circuit, IC13 is wired as a monostable multivibrator, having time periods of around 5 seconds. You can change the time period of IC1 by changing the values of resistor R2 and capacitor C1.

Alphanumeric displays IC1 to IC12 are wired, such that they show “HAPPY NEW YEAR” when the output of IC13 goes high. The circuit is powered by a 6V battery. Else, you can use the 6V, 300mApower adaptor that is readily available in the market. The 6V battery or power adaptor provides regulated 6V required to operate the circuit. A 6V DC socket is used in the circuit to connect the output of the adaptor if you don’t use the battery.

Working of the circuit is simple. First, power-on the circuit using switch S2. LED1 glows to indicate presence of power supply in the circuit. IC13 produces a high output at its pin 3 for about two minutes. Transistor T1 conducts to enable the alphanumeric displays. The word “HAPPY NEW YEAR” is displayed for about two minutes as IC1 to IC12 are ground via transistor T1.