Password Based Electronic Lock

In a world where security is becoming more important every day, building your own electronic password-based lock is not just a rewarding project — it’s also a practical one. In this post, I’ll walk you through how I built a simple but effective electronic lock system using the classic CD4013 (D Flip-Flop) and CD4011 (Nand Logic) ICs — all without a microcontroller

How It Works:

This lock operates on a fixed-sequence password using pure logic gates and flip-flops:

After the final correct key is pressed, the last flip-flop outputs a HIGH signal to unlock the system (e.g., light up an LED or activate a relay)

Each button is tied to a logic combination.

When the correct buttons are pressed in the right order, the logic gates (CD4011) enable a chain of CD4013 flip-flops to advance.

Pressing the wrong button at any stage triggers the reset line, which clears the flip-flops and starts over.

Components Required:

• CD1013 IC
• CD4017 IC
• Push Button
• Power Supply 3.7v-5v
• Resistor 1k Ohm
• Capacitor 10uf
• Solenoid Door Lock

Gerber File:

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CD1013 IC:

The CD1013 is a dual general-purpose operational amplifier (op-amp) IC. It is commonly used in analog signal processing tasks like amplification, filtering, and mathematical operations such as addition, subtraction, integration, and differentiation. It is similar in function to the popular LM358 op-amp.

Key Features:

• Dual op-amp: Contains two independent op-amps in a single package.
• Wide voltage range: Operates typically from a single supply (e.g., +3V to +32V) or dual supply (e.g., ±1.5V to ±16V).
• Low power consumption.
• Internally frequency compensated.
• Suitable for battery-operated devices.

Applications:

• Audio preamplifiers
• Active filters
• Oscillators
• Comparators
• Signal conditioning circuits
• Voltage followers (buffers)

CD4017 IC:

The CD4017 is a decade counter/divider IC with 10 decoded outputs. It is widely used in electronics projects for sequencing purposes—like LED chasers, timers, and digital counters.

🔧 Key Features of CD4017:

• 10 Decoded Outputs (Q0 to Q9): Each goes high in sequence on every clock pulse.
• Clock Input: Advances the counter on each rising edge.
• Divide-by-10 Counter: Returns to Q0 after Q9.
• Reset and Enable Pins: Used to reset the counter or control clock response.
• Low Power CMOS: Wide voltage range and low power consumption.

How It Works:

When the clock pin (14) receives a rising edge, the next output pin (Q0 to Q9) goes high, and the previous goes low.

• The reset pin (15) resets the counter to Q0 when driven high.
• The clock enable pin (13) must be low for the counter to respond to the clock.

Common Applications:

LED chasers or sequencers

• Light effects
• Digital counters (0–9)
• Frequency dividers
• Timers or event counters

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