The 7490 is a versatile decade counter integrated circuit that can count from 0 to 9, making it ideal for various counting applications in digital electronics. In this DIY project, we’ll guide you through building a simple decade counter using the 7490, which can be used to count pulses from a push button switch or a clock signal.

What You’ll Need
7490 IC (Decade Counter)
Breadboard
Jumper Wires
LEDs (10)
Resistors (220Ω)
Push Button Switch
Capacitor (10µF for debouncing)
Power Source (e.g., 5V DC supply)
Multimeter (optional for testing)
Understanding the 7490
The 7490 is a BCD (Binary-Coded Decimal) counter, meaning it counts from 0 to 9 in binary form (0000 to 1001). The counter has ten output pins (Q0 to Q3) that represent the count value in binary, and it can be reset to zero with a reset signal. When it counts to 10, it resets back to 0, making it perfect for counting applications.

Wiring the Components
Insert the IC: Place the 7490 IC onto the breadboard. Make sure the notch or dot indicating pin 1 is facing you.

Connect Power and Ground: Connect pin 14 (VCC) to the positive terminal of your power supply (+5V) and pin 11 (GND) to ground.

Setup Output LEDs: Connect LEDs to the output pins:

Q0 (pin 3) to LED1 through a 220Ω resistor.
Q1 (pin 2) to LED2 through a 220Ω resistor.
Q2 (pin 4) to LED3 through a 220Ω resistor.
Q3 (pin 10) to LED4 through a 220Ω resistor.
Connect the cathodes of all LEDs to ground.
Connect the Clock Input: Connect the push button switch to pin 14 (the clock input). Place a 10µF capacitor between the switch and ground to debounce the switch and prevent erratic counting.

Reset Connections: To enable the counter to reset, connect pin 6 (reset) to ground through a resistor. To reset the counter, you can briefly connect this pin to VCC.

Circuit Functionality
When the circuit is powered, pressing the push button switch sends a pulse to the clock input of the 7490. Each press increments the count by one. The output pins will light up the corresponding LEDs based on the current count in binary. For instance, if the counter reads 3 (0011 in binary), the first four LEDs will light up in a specific pattern.

Testing the Circuit
Once you have everything connected, power the circuit and press the push button. You should see the LEDs light up in a binary sequence as you press the button, counting from 0 to 9. If you press the button 10 times, the counter should reset back to 0, demonstrating its decade counting capability.

Optional Enhancements
For those looking to expand their understanding, consider these enhancements:

Frequency Generation: Replace the push button with an astable multivibrator circuit to create a continuous clock signal, allowing the counter to increment automatically.
Display Outputs: Use a 7-segment display driver IC to visually represent the count in decimal form rather than binary.
Chaining Counters: Connect multiple 7490 ICs to create a multi-digit counter that can count beyond 9, allowing you to explore larger counting systems.
Conclusion
Building a decade counter with the 7490 IC is a fantastic way to understand digital counting circuits. This project not only teaches you about binary counting but also provides a foundation for more complex electronics applications. Whether for educational purposes or as a stepping stone to larger projects, mastering the 7490 will enhance your electronics skills significantly. Happy counting!