It is very simple and easy to construct project which will display random numbers from 0 to 7 on a 7 segment display. This random number generator circuit can serve as an alternative that can be used to replace the traditional dice while playing games such as snake ladder, monopoly etc. It uses NE555 which is a well known multivibrator IC. Here 555 timer IC is wired as an astable oscillator which provide a clock pulse to CD4017 IC.CD4017 which is a medium speed Johnson Counter that works at 10MHz and has 10 decoded outputs. CD4017 ICs are widely used in frequency dividers, binary counters, divide by N counters and register design applications and CD4511 which is a BCD to 7 segment decoder.
Fig. 1: Prototype Of Random Number Generator Using 7 Segment Display
This random number generator circuit is based on three IC’s namely NE555, CD4017 and CD4511 with few more components.
In this circuit, NE555 astable generates a clock for the circuit, which provides an oscillating wave to the output pin 3 of IC1. You can vary the speed of oscillation with the help of VR1. The frequency of oscillation of 555 timer can be calculated by-
CD4017 is a CMOS counter/ divider IC. It takes the clock signal from t from pin3 of IC1
and turns on the 10 output in sequence, each time when it receives clock input pulses.
CD4511 is a CMOS BCD to seven segment latch/decoder. This IC provides the functions of a 4-bit storage latch, an 8421 BCD-to-seven segment decoder, and an output drive capability. It also provide you the of facility lamp test . It is used to check that all segments of 7 segment are working properly or not. For testing, momentarily make the pin low, in short used to test the display.
Blanking input is use to turn off or vary the brightness of the display. Latch enable (LE) is used to store BCD codes. CD4511 is used in various application like in clock, watches,
computer, calculators etc.
When 555 timer output from pin 3 is applied to CD4017 decade counter pin 14 provides
a clock for the working of IC2. Here, after receiving the clock input, CD4017 starts its
counter from zero.
It advances one by one each time pin 14 goes high. For instance, first we get output from pin3
(Q0) then from pin 2 ( Q1) , so on. As we are get continuous pulses from NE555, when switch is pressed pin 14 goes high, we see the corresponding number on 7 segment display. From the circuit diagram, you can see that we have connected pin 5 (Q6 output) to reset pin 15 so, we will receive numeric number from 0 to 7.
We are getting binary output from CD4017 that can be converted into numeric value with the help of CD4511 IC and a 7 segment common cathode display. We have connected the resistor R5 to R11 between CD4511 output and 7 segment display because, each LED segment requires its own voltage drop. If you don’t connect a resistor, it will destroy that section. Also remember that IC 4511 is used only for common cathode display.
You can also use LED’s at the output if you don’t have CD4511 and 7 segment display.