Electronic Coin Toss Circuit using IC 555 and JK Flip-Flop

Many times people make choice by flipping coin.

But this method is not always fair but sometimes it give biased result.

To fix this we can use Electronic Coin Toss Circuit using IC 555 and JK Flip-Flop.

It works like real coin flip using digital technology and LED.

This circuit has two main parts:

• IC 555 timer
• IC 74LS76 (dual JK flip-flop)

In the circuit diagram below IC1 555 runs as astable multivibrator at 10Hz and IC2 74LS76 set to toggle and works as needed.

Circuit Working:

Parts List:

IC1 555 Timer works as astable multivibrator as it makes square wave signal ON/OFF at set speed.

It keeps sending pulses again and again.

Transistor Q1 BC547 works like switch, when we press button S1 as it turns ON the JK flip-flop IC2 74LS76.

Button S1 gives trigger pulse to IC2 and IC2 holds the toss result and controls LEDs.

Because IC1 runs fast IC2 changes state fast and looks random.

Flip-flop output controls two LEDs with one LED lights up based on final flip-flop state.

S1 starts the toss.

High speed pulse makes LED choice look random like fair coin flip.

Note:

• Red LED (Heads) is pin 14
• Green LED (Tails) is pin 15

Formulas:

To make our own circuit we used this formula for 555 Timer:

555 Timer Frequency Formula:

f = 1.44 / ((R1 + 2×R2) × C1)

where,

R1 is 47k
R2 is 47k
C1 is 1µF

How to Build:

To build a Electronic Coin Toss Circuit using IC 555 and JK Flip-Flop following steps need to be followed:

• Connect pin 1 of IC1 555 to GND
• Join pin 2 and pin 6 of IC1 together
• Connect C1 positive to pin 2 and negative to GND
• Connect pin 3 of IC1 to base of Q1 BC547 using R3
• Connect pin 4 and pin 8 of IC1 to +5V supply
• Connect pin 5 of IC1 to GND using capacitor C2
• Place resistor R2 between pin 6 and pin 7
• Place another R2 between pin 7 and +5V
• Connect collector of Q1 to +5V using R4
• Connect emitter of Q1 to GND
• Connect pin 1 of IC2 74LS76 to collector of Q1 through S1 switch
• Add R5 from pin 1 of IC2 to GND
• Connect pin 4, pin 5 and pin 16 of IC2 to +5V
• Connect pin 13 of IC2 to GND
• Connect pin 14 of IC2 to +5V through LED2 (Red Heads) and R6
• Connect pin 15 of IC2 to +5V through LED1 (Green Tails) and R7

Conclusion:

This Electronic Coin Toss Circuit using IC 555 and JK Flip-Flop removes unfair coin flips.

It gives random and equal result.

LEDs show Heads or Tails.

It is good project for students and hobby people to learn timers and flip-flops in digital circuits.

References:

DUAL J-K FLIP-FLOPS WITH PRESET AND CLEAR