Digital code lock

Description.

This is a simple but effective code lock circuit that has an automatic reset facility. The circuit is made around the dual flip-flop IC CD4013.Two CD 4013 ICs are used here. Push button switches are used for entering the code number. One side of all the push button switches are connected to +12V DC. The remaining end of push buttons 2,3,6,8 is connected to clock input pins of the filp-flops. The remaining end of other push button switches are shorted and connected to the set pin of the filp-flops.

The relay coil will be activated only if the code is entered in correct sequence and if there is any variation, the lock will be resetted. Here is correct code is 2368.When you press 2 the first flip flop(IC1a) will be triggered and the value at the data in (pin9) will be transferred to the Q output (pin13).Since pin 9 is grounded the value is “0” and so the pin 13 becomes low. For the subsequent pressing of the remaining code digits in the correct sequence the “0” will reach the Q output (pin1) of the last flip flop (IC2b).This makes the transistor ON and the relay is energised.The automatic reset facility is achieved by the resistor R11 and capacitor C2.The positive end of capacitor C2 is connected to the set pin of the filp-flops.When the transistor is switched ON, the capacitor C2 begins to charge and when the voltage across it becomes sufficient the flip-flops are resetted. This makes the lock open for a fixed amount of time and then it locks automatically. The time delay can be adjusted by varying the values of R11 and C2.

Circuit diagram with Parts list

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Simple Electronic Combination Lock (IC LS 7220)

Description

This is the circuit diagram of a simple electronic combination lock using IC LS 7220.This circuit can be used to activate a relay for controlling (on & off) any device when a preset combination of 4 digits are pressed.The circuit can be operated from 5V to 12V.

To set the combination connect the appropriate switches to pin 3,4,5 and 6 of the IC through the header.As an example if S1 is connected to pin 3, S2 to pin 4 , S3 to pin 5, S4 to pin 6 of the IC ,the combination will be 1234.This way we can create any 4 digit combinations.Then connect the rest of the switches to pin 2 of IC.This will cause the IC to reset if any invalid key is pressed , and entire key code has to be re entered.

When the correct key combination is pressed the out put ( relay) will be activated for a preset time determined by the capacitor C1.Here it is set to be 6S.Increase C1 to increase on time.

For the key pad, arrange switches in a 3X4 matrix on a PCB.Write the digits on the keys using a marker.Instead of using numbers I wrote some symbols!.The bad guys will be more confused by this.

Circuit Diagram

Pin Assignment of LS7220

Parts List 

C1                           1   1uF 25V Electrolytic Capacitor

C2                           1    220uF 25V Electrolytic Capacitor

R1                           1    2.2K 1/4W Resistor

Q1                          1    2N3904 NPN Transistor    2N2222

D1                           1    1N4148 Rectifier Diode    1N4001-1N4007

K1                           1    12V SPDT Relay    Any appropriate relay with 12V coil

U1                          1     LS7220 Digital Lock IC

S1-S12                   12    SPST Momentary Pushbutton    Keypad (see notes)

HD1                        1    12 Position Header

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3 Input Mic Mixer Circuit

Here is a simple 3 input mic mixer circuit using the popular uA 741 ICs. Four 741s are used here.IC1, IC2, IC3 are used as preamplifiers. They produce a gain of around 40 decibel to the individual input signals. The IC4 is wired as a summing amplifier to add the signals from three preamplifiers.IC4 also gives a gain of around 5decibel to the final output signal. Total gain of the system is around 45decibel.

Notes.

• Assemble the circuit on a good quality PCB.
• A +15/-15 V DC dual power supply is needed for powering the circuit.
• All inputs and output must be connected with respect to the ground.
• ICs must be mounted on holders.
• Electrolytic capacitors C1, C2 and C3  must be rated 10V and other capacitors  must be 30V.

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Musical Bell (UM 66)

This circuits uses very few component and gives melody sound. It uses 3 terminal IC UM66 and can be build small enough to be placed inside a greeting card and operated off a single 3V flat button cell.

There is not much to the circuit. The UM66 is connected to its supply and its output fed to a transistor for amplification. Any common speaker can be used or a “flat” piezoelectric tweeter like the one found in alarm wrist watches. If you use the piezo, then it can be connected directly between the output pin 1 and ground pin 3 without the transistor.

The UM66 looks like a transistor with 3 terminals. It is complete miniature tone generator with a tune. Now they come with wide variety of different tunes.

For amplification we have used a NPN transistor which is BC548. Here BC548 makes a common emitter circuit. For limiting the base current we have used a resistance of 220 Ohms so that transistor will not get damaged by excess current.

PROCEDURE :

1. Draw circuit diagram on ply board and make hole with compass or broader for component pin insertion.

2. Identify emitter base collector of transistor and pin no. of IC UM66

3. Solder all parts according to the circuit. You will need soldering iron, Soldering flux and flexible wire.

4. Make sure all points are well soldered according to the Circuit Diagram and no dry solders. Wrong connection of IC may heat up and get damage.

5. After loading battery power ON the circuit. Now you can check the function of the project.

OR

• D400 - 1
• UM66 - 1
• 1k - 1
• speaker - 1

With an integrated series UM66TXX can get different melodies that are attached to the table.

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The Universal Timer

Now, a day automation task is necessity not only in industrial sphere but even in the domestic sphere.

The project universal timer in this website is unique because it offer an ultra wide range of time period having pin point precision anywhere (i.e. not affected by ant physical factor) from one – tenth of a second to hundreds of hours. Due to feature “auto latch” facilities and low power consumption CMOS IC used plus such a low current consumption on that most multimeter would fail to detect it. The above facility with low costlier and familiar design make the circuit “The Universal Timer ” more versatile.

Circuit description of universal timer

High frequency signal of several kilohertz is generated by IC1 CD4060, and VR1 is used to remove device imprecision errors. The internal frequency divider of IC1 divides the base frequency by a factor of 213 times i.e. 16384 times.

The output frequency of 10 KHz from pin 3 of IC1 is simultaneously divided by set of five CD4017 counters (IC2 – IC6) by 10, 6, 10, 6, and 10. Here IC2 to IC6 is configuring in maximum mode and divided-by-six decimal mode respectively where output is selected by range selector switch SW1.

The output time period from range selector of universal timer switch is 0.1 second, 1 second, 0.1 minute, 1 minute, 0.1 hour, 1 hour respectively given to two serial connected counter CD4017 (IC7, IC8). The outputs from range selector provide precise master clock frequency, counted by IC7 and IC8. IC7 and IC8 counts one and ten master pulses respectively.

The timer section of universal timer is control by two rotator switch SW2 and SW3 as shown in circuit diagram figure 1.

NAND gate N1 is used to change the state of output from SW2 and SW3. The feedback diode D1 helps to latches the next NAND gate N2.

Lastly a relay driver transistor T1 is used to drive relay connected to collector of transistor T1. The relay contacts can be selected to switch the load ‘ON’ or ‘OFF’ after the preset time. Switch SW4 (Push-To-On switch) is used to reset the whole circuit. Power supply interruption also reset the entire circuit of universal timer.

NOTE: Connect a device to a timer and set it to short period, say a few seconds, and adjust VR1 till exactly that time delay is obtained. The accuracy on rest of the range will follow automatically.

PARTS LIST

Resistors (all ¼-watt, ± 5% Carbon)

R1 – R4, R10, R11 = 1 KΩ

R5, R6 = 10 KΩ

R7 = 47 KΩ

R8 = 24 KΩ

R9 = 100 Ω

VR1 = 4.7 KΩ

Capacitors

C1 = 0.0001 µF ceramic

C2 = 100 µF/25V electrolytic

Semiconductors

IC1 = CD4060

IC2 – IC8 = CD4017

IC7 (N1 – N2) = CD4011

T1 = BC547 NPN transistor

D1 – D3 = 1N4148

Miscellaneous

SW1 = Single–pole 6–way rotary switch

SW2, SW3 = Single–pole 10–way rotary switch

SW4 = Push-To-On switch

SW5 = On/Off switch

SW6 = SPDT (Single pole double throw)

RL1 = 300 Ω 12V relay

LED1 = RED

LED2 = Green

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XS1B (Motor Bike)Wiring Diagram

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5 channel radio remote control

TX-2B / RX / 2B  5 channel radio remote control.

This article is about a simple 5 channel radio remote control circuit based on ICs TX-2B and RX-2B from Silan Semiconductors. TX-2B / RX-2B is a remote encoder decoder pair that can be used for remote control applications. TX-2B / RX-2B has five channels, wide operating voltage range (from 1.5V to 5V), low stand by current (around 10uA), low operating current (2mA), auto power off function and requires few external components. The TX-2B / RX-2B was originally designed for remote toy car applications, but they can be used for any kind of remote switching application.

Circuit diagrams and description.

Remote encoder / transmitter circuit.

The TX-2B forms the main part of the circuit. Push button switches S1 to S5 are used for activating (ON/OFF) the corresponding O/P channels in the receiver / decoder circuit. These push button switches are interfaced to the built-in latch circuitry of the TX-2B. Resistor R7 sets the frequency of the TX-2B’s internal oscillator. Resistor R1 and Zener diode D1 forms a simple Zener regulator circuit for providing the IC with 3V from the 9V main supply. C2 is the filter capacitor while C1 is a noise by-pass capacitor. D2 is the power on indicator LED while R6 limits the current through the same LED. S1 is the ON/OFF switch. The encoded control signal will be available at pin 8 of the IC. The encoded signal available at pin 8 is without carrier frequency. This signal is fed to the next stage of the circuit which is a radio transmitter. Crystal X1 sets the oscillator frequency of the transmitter section. R2 is the biasing resistor for Q1 while R3 limits the collector current of Q1. The encoded signal is coupled to the collector of Q1 through C3 for modulation. Transistor Q2 and associated components provide further amplification to the modulated signal.

Remote receiver / decoder circuit.

The remote receiver circuit is built around the IC RX-2B. The first part of the circuit is a radio receiver built around transistor Q1. The received signal is demodulated and fed to pin 14 of the IC. Pin 14 is the input of the built in inverter inside the IC. R2 sets the frequency of the IC’s internal oscillator. O/P 1 to O/5 are the output pins that are activated corresponding to the push buttons S1 to S5. Zener diode D1 and resistor R12 forms an elementary Zener regulator for supplying the RX-2B with 3V from the 9V main supply. C12 is the filter capacitor while R11 is the current limiter for the radio receiver section. Diode D2 protects the circuit from accidental polarity reversals. C15 is another filter capacitor and C14 is a noise by-pass capacitor.

Notes.

§  This circuit can be assembled on a vero board or a PCB.

§  Use 9V DC for powering the transmitter / receiver circuits.

§  Battery is the better option for powering the transmitter / receiver circuit.

§  If you are using a DC power supply circuit, it must be well regulated and free from any sort of noise.

§  Both ICs must be mounted on holders.

Interfacing relay to the RX-2B output.

The method for interfacing a relay to the output of RX-2B is shown below. When push button switch S1 of the transmitter circuit is pressed, pin O/P1 (pin 7 of the RX-2B) goes high. This makes the transistor 2N2222 to conduct and the relay is activated. The same technique can be applied to other output pins of the RX-2B. The relay used here is a 200 ohm type and at 9V supply voltage the load current will be 45mA which is fine for 2N2222 whose maximum possible collector current is 900mA. When using relays of other ratings this point has to be remembered and do not use a relay that consumes a current more than the maximum possible collector current of the driver transistor.

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Seven Segment Counter Display Circuit

Here is the circuit diagram of a seven segment counter based on the counter IC CD 4033.This circuit can be used in conjunction with various circuits where a counter to display the progress  adds some more attraction.
IC NE 555 is wired as an astable multivibrator for triggering the CD 4033.For each pulse the out put of CD 4033 advances by one count.The output of CD 4033 is displayed by the seven segment LED display LT543.Switch S1 is used to initiate the counting.Diode D1 prevents the risk of accidental polarity reversal.

Seven Segment Circuit Diagram with Parts List.

 

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IR Burglar Alarm for Basic Home security system

IR based entry detector alarm is useful for someone crosses the Gate or door of house when is left open.. It can alarm you and notify you that someone entered into the door or place.. This project will be used at Doors/ Entrance of office to get alert the owner or admin to notify someone crossed the gate or door of the location.

IR LED will send and receives signal when some one interrupts the IR signal alarm will be started to make alert of any burglar or theft.

 

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Cable LAN Tester Circuit

Here iscable LAN testercircuit. Thecable LAN testercircuit can also to test cable on telephone, coaxial cable, Lan cable and other. Thiscable LAN testercircuit using led for main indicator device. This simple cable LAN tester circuit, can be make in home. Designed initially for my intercom, but can be used with alarm wiring, CAT 5 cables and more. As the 4017 has limited driving capabilities, then each output is buffered by a 4050. This provides sufficient current boost for long cables and the transmitter and receiver LED's. The receiver is simply 8 LED's with a common wire…read on. The cable LAN tester circuit comprises transmitter and receiver, the cable under test linking the two. The transmitter is nothing more than a "LED chaser" the 4011 IC is wired as astable and clocks a 4017 decade counter divider. The 4017 is arranged so that on the 9th pulse,the count is reset. Each LED will light sequentially from LED 1 to LED 8 then back to LED 1 etc. Note also that as the CMOS 4050 is only a hex buffer, you need 8 gates so two 4050′s are required, the unused inputs are connected to ground (battery negative terminal). Please note that for clarity this cable LAN tester?circuit has been drawn without showing power supplies to the CMOS 4011 and CMOS 4050 IC’s. The positive battery terminal connects to Pin 14 of each IC and negative to Pin 7. The CMOS 4017 uses Pin 16 and Pin 8 respectively.

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