Digital Combination LockCircuit Project Tutorial

Posted on Feb 4, 2014

The circuit above makes use of the CMOS 4017 decade counter IC. Each depression of a switch steps the output through 0 - 9. By coupling the output via an AND gate to the next IC, a predefined code has to be input to create the output. Each PBS switch is debounced by two gates of a CMOS4001 quad 2-input NOR gate. This ensures a clean pulse to the i

Digital Combination LockCircuit Project Tutorial

Click here to download the full size of the above Circuit.

nput of each CMOS 4017 counter. Only when the correct number of presses at PBS A will allow PBS B to become active. This is similar for PBS C and PBS D. At IC4, PBS D must be pressed 7 times. Then PBS C is again pressed 7 times, stepping from output 1 to output 8. The AND gate formed around CMOS4081 then goes high, lighting the LED. The Reset switch can be pressed at any time. Power on reset is provided by the 100n capacitor near the reset switch.

Visit page

Leave Comment

characters left:

Related Circuits

Cell Phone Controlled Home Appliance circuit

Ever Imagined controlling your home appliances using your cell phone. You can find a lot of circuits for this application. But they make use of Telephone. I modified the circuit and redesigned it...

Circuit for controlling 8 appliances using TV Remote

The IR circuit can be used to switch devices using TV Remote. Normal circuits can switch only one device. But using this circuit, different devices can be controlled using same remote with...

Serial COM port using ATmega8

Many times, I have written code for UART communication and when it came to testing, my laptop does not have a serial port. I bought a USB to serial port converter but it didnt worked. I felt...

de amst wiskar: robot line folower

One of my student has made a disgraceful robot that used two stepper motors and with a simple IR sensor. Yes, above picture is what I`m talking. Without battery carrying, a little bit torque of the...

Dual cable (serial + USB) for Nikon coolpixes

To assure that USB and serial segments are electrically isolated, we used an optocoupler (U1). The LED section of U1 is driven directly by DTR, so we should select a very sensitive optocoupler to...

classic led flasher circuit

This LED flasher circuit is a classic two transistor flip flop. This flasher circuit is very popular and it`s usually the first circuit to build when starting electronic circuit building hobby....

ac-motor-control-circuits

Perhaps the most challenging aspect of interpreting ladder diagrams, for people more familiar with electronic schematic diagrams, is how electromechanical relays are represented. Compare these two...

Stamp9G20

This document was written with care, but errors cannot be excluded. Neither the company named above nor the seller assumes legal liability for mistakes, resulting operational errors or the...

New Circuits

Zero consumption Anti-theft High power Code Switch for E-Bike Batteries

This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
Ultrasonic distance finder circuit

The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Simple Metal detector circuit with CD4030

Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Fully automatic watering circuit for flower pots

Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
Simple deep searching metal detector circuit

The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
Sub-Harmonic Bass Converter for Electric Guitars

The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
Echo Depth Sounding Sonar for Boats

In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
100W HiFi Audio Amplifier Circuit

This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
Plant-Pot Water Level Indicator Circuit

A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....

Create NOW your QR MENU for your Restaurant / Hotel / Bar / Caffe,

Comprehensive ordering/paying features. fully personalized to suit your Business.

Update Anytime! Easy and Simple!

Popular Circuits

Precision-full-wave-rectifier

This circuit provides accurate full-wave rectification. The output impedance is low for both...

Dark-Activated Alarm With Pulsed Tone Output Circuit

NOR gates a and b form a low-frequency oscillator that is activated when the CDS cell, under...

Ultrasonic range finder circuit

The circuit is designed to be low cost. It uses a PIC12C508 to perform the control functions and...

arduino temperature and light sensor

This device just sends data about the state of our office to Twitter (mainly because it`s just...

Temperature controlled DC fan

Here is a simple circuit based on two transistors that can be used to control the speed of a 12 V...