Monday, September 15, 2014
Digital Electronic Lock Wiring diagram Schematic
This Digital Electronic Lock Circuit Diagram shown below uses 4 common logic ICs to allow controlling a relay by entering a 4 digit number on a keypad. The first 4 outputs from the CD4017 decade counter (pins 3,2,4,7) are gated together with 4 digits from a keypad so that as the keys are depressed in the correct order, the counter will advance. As each correct key is pressed, a low level appears at the output of the dual NAND gate producing a high level at the output of the 8 input NAND at pin 13.
Digital Electronic Lock Circuit Diagram
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Digital Electronic Lock Circuit Diagram
The momentary high level from pin 13 activates a one shot schema which applies an approximate 80 millisecond positive going pulse to the clock line (pin 14) of the decade counter which advances it one count on the rising edge.
A second monostable, one shot schema is used to generate an approximate 40 millisecond positive going pulse which is applied to the common point of the keypad so that the appropriate NAND gate will see two logic high levels when the correct key is pressed (one from the counter and the other from the key). The inverted clock pulse (negative going) at pin 12 of the 74C14 and the positive going keypad pulse at pin 6 are gated together using two diodes as an AND gate (shown in lower right corner).
The output at the junction of the diodes will be positive in the event a wrong key is pressed and will reset the counter. When a correct key is pressed, outputs will be present from both monostable diagram (clock and keypad) causing the reset line to remain low and allowing the counter to advance. However, since the keypad pulse begins slightly before the clock, a 0.1uF capacitor is connected to the reset line to delay the reset until the inverted clock arrives.
The values are not critical and various other timing schemes could be used but the clock signal should be slightly longer than the keypad pulse so that the clock signal can mask out the keypad and avoid resetting the counter in the event the clock pulse ends before the keypad pulse. The fifth output of the counter is on pin 10, so that after four correct key entries have been made, pin 10 will move to a high level and can be used to activate a relay, illuminate an LED, ect. At this point, the lock can be reset simply by pressing any key. The schema can be extended with additional gates (one more CD4011) to accept up to a 8 digit code.
The 4017 counting order is 3 2 4 7 10 1 5 6 9 11 so that the first 8 outputs are connected to the NAND gates and pin 9 would be used to drive the relay or light. The 4 additional NAND gate outputs would connect to the 4 remaining inputs of the CD4068 (pins 9,10,11,12). The schema will operate from 3 to 12 volts on 4000 series CMOS but only 6 volts or less if 74HC parts are used. The schema draws very little current (about 165 microamps) so it could be powered for several months on 4 AA batteries assuming only intermittent use of the relay.
Friday, November 2, 2012
Freeze Protector Circuit
This is the simple freeze protector circuit diagram. It is also called timing circuit. It is just hobby project for beginners. When you need to operate automatically any device in the fixed time later after coming AC power supply, you can use this circuit.
The voltage amplitude
is high when AC power come. Suddenly high voltage destroys the
electronics device. For this reason, in the time of load shedding we
need to switched off electronics device (Audio/Video player, CD/DVD
Player, TV, Freeze or any electronics device). This circuit solve this problem.
Hobby Electronics helps the beginners to know the timing circuit specially using 555 IC
timer. NE555 IC is the very simple well known parts. Its configuration
is very simple. You can use this timer any simple circuit.
In this circuit use 12volt
power supplies. 300k variable resistor is used for timing control.
Timing resistor and capacitor are 300k and 1000uF. Only change the value
of the variable resistor for your required timing.
The circuit output pin 3 is connected with resistor (10k) and output 12 volt relay. Relay is connected as figured with the device. Making cost is too low. Anyone can make this circuit easily.
Complete Room Securty System Circuit diagram
This simple circuit is called room security system circuit. The main purpose of this circuit is to secure your room in night. You need not any security guard. When any unwanted person wants to enter your room in night then this circuit raised alarm. On the other benefit, it is always activated on load shedding.
There are five separates parts in this circuit – regulated power supply, relay driver, door switching, alarm system and audio amplifier. First section is regulated power supply. The output of IC 7809 is regulated +9Volt which is converted from 9Volt unregulated power supply. Capacitors are used for removing ripple. A full wave 9 volt transformer is connected in the input of this power section.
The second part is relay driver. Q1 transistor is used for driving relay. When the Q1 transistor is forward bias then the relay is ON and the total circuit gets positive voltage from ac source. In the time of load shedding relay is deactivated and the total circuit gets power from 6Volt Battery.
Continue Reading here[...]
There are five separates parts in this circuit – regulated power supply, relay driver, door switching, alarm system and audio amplifier. First section is regulated power supply. The output of IC 7809 is regulated +9Volt which is converted from 9Volt unregulated power supply. Capacitors are used for removing ripple. A full wave 9 volt transformer is connected in the input of this power section.
The second part is relay driver. Q1 transistor is used for driving relay. When the Q1 transistor is forward bias then the relay is ON and the total circuit gets positive voltage from ac source. In the time of load shedding relay is deactivated and the total circuit gets power from 6Volt Battery.
The third part is door switching. When C1 capacitor’s two terminals are short, transistor Q2 is reversed
biased. So Q2 transistor is OFF. When C1 capacitor’s two terminals are
open, transistor Q2 is forward biased. So Q2 transistor is ON. For this
reason IC UM66 is ON and it
generates music which is feed another two transistors Q3 and Q4. A
speaker is connected with collector of the transistor Q4 as circuit
diagram.
Automatic Street Light Controller Circuit Diagram
This circuit is an automatic street light controller. Sensors used to detect changes in light is LDR (Light dependent resistor), the working principle of Light dependent resistor
is exposed to light when the resistance value of LDR great, but if not
exposed to light or dark then the resistance value of LDR.
LDR is a special type of resistance whose value depends on the brightness of the light which is falling on it. It has resistance of about 1 mega ohm when in total darkness, but a resistance of only about 5k ohms when brightness illuminated. It responds to a large part of light spectrum.
When light falls on the LDR then its resistance decreases which results in increase of the voltage at pin 2 of the IC 555. IC 555 has got comparator
inbuilt, which compares between the input voltage from pin2 and 1/3rd
of the power supply voltage. When input falls below 1/3rd then output is
set high otherwise it is set low. Since in brightness, input voltage
rises so we obtain no positive voltage at output of pin 3 to drive relay.
Continue Reading here[...]
LDR is a special type of resistance whose value depends on the brightness of the light which is falling on it. It has resistance of about 1 mega ohm when in total darkness, but a resistance of only about 5k ohms when brightness illuminated. It responds to a large part of light spectrum.
Mobile Incoming Call Indicator Circuit Diagram
this circuit can be used to escape from the nuisance of mobile phone rings
when you are at home. This circuit will give a visual indication if
placed near a mobile phone even if the ringer is deactivated.
When a call is coming to the mobile phone, the transmitter inside it becomes activated. The frequency of the transmitter is around 900MHz.The coil L1 picks up these oscillations by induction and feds it to the base of Q1. This makes the transistor Q1 activated.Since the Collector of Q1 is connected to the pin 2 of IC1 (NE555) , the IC1 is triggered to make the LED connected at its output pin (pin 3) to blink. The blinking of the LED is the indication of incoming call.
Notes:
Continue Reading here[...]
When a call is coming to the mobile phone, the transmitter inside it becomes activated. The frequency of the transmitter is around 900MHz.The coil L1 picks up these oscillations by induction and feds it to the base of Q1. This makes the transistor Q1 activated.Since the Collector of Q1 is connected to the pin 2 of IC1 (NE555) , the IC1 is triggered to make the LED connected at its output pin (pin 3) to blink. The blinking of the LED is the indication of incoming call.
Notes:
- The coil L1 can be made by making 150 turns of 36 SWG enameled copper wire on a 5mm dia plastic former.Or you can purchase a 10 uH coil from shop if available.
- The circuit can be powered from a 6V battery.
- Assemble the circuit on a good quality PCB.
- C1 & C3 are to be polyester capacitors.
- The electrolytic capacitor C2 must be rated 10V.
4017 LED Knight Rider Running Light Circuit Diagram
In this 4017 Knight Rider circuit, the 555 timer is
wired as an oscillator. It can be adjusted to give the desired speed
for the display. The output of the 555 is directly connected to the
input of a Johnson Counter (CD 4017).
Continue Reading here[...]
The
input of the counter is called the CLOCK line. The 10 outputs become
active, one at a time, on the rising edge of the waveform from the 555. Each output can deliver about 20mA but a LED should not be connected to the output without a current-limiting resistor (220Ω in the circuit above).
The
first 6 outputs of the chip are connected directly to the 6 LEDs and
these “move” across the display. The next 4 outputs move the effect in
the opposite direction and the cycle repeats. The animation above shows
how the effect appears on the display. Using six LEDs,
the display can be placed in the front of a model car to give a very
realistic effect. The outputs can be taken to driver transistors to
produce a larger version of the display.
Digital Object Counter using LDR and digital IC 7490
This is the simple circuit on Hobby Electronics. In this circuit three modules are used in object counter. 555 timer are used as a monostable mode and astable mode. The other is counter module.
In this circuit 555 timer configured as a monostable mode, is a simple automatic dark sensor circuit that gives output when light falling is blocked on LDR. Pin 3 of monostable circuit has been connected to pin 4 of astable timer. When monostable circuit generates output, astable mode timer starts giving pulses to the counter module. Frequency for counter module is set up using R4, R3 and C2. 
Continue Reading here[...]
7490acts as a decade counter and 7447 uses the output of 7490
to display numbers on seven segment display. This circuit counts from 0
to 9. You can count 0 to 100 modifying counter module circuit. Just
adding few components as well as two counter ic, two display driver and two display. For count 0 to 100, comments on the comments box. You will get complete circuit.
The output will be: If you block light falling on LDR, the number on seven segment display will increase.
A Small project on Battery level Indicator
Working principle of this circuit is battery voltage compared with the reference voltage. This circuit is constructed by using 741 op-amp ICs. Op-amp is differential amplifier which output will be positive or negative, depends on the difference of input voltages.
When the input voltage difference is positive with respect to reference voltage and battery voltage, then the output is positive and the LED will emit light. If negative LED cannot emit light. It is the main principle of battery level indicator.
Voltage level indicated by the column of LEDs. For easy of reading LED rearranged in a vertical array.
The top four LEDs indicates the battery voltage is high. Sequentially the lower level indicates the battery voltage is low and bottom four LEDs indicates very low voltage of the battery. So, if the battery voltage continues to decline then LEDs will die in sequence from top to bottom. In this circuit 1mA current is adjusted for reference voltage. Vcc is divided by the total number of resistor for finding the value of resistor R. On the other hand, the resistor value of R1 is calculated by the equation,
Component:
1. Op-amp IC 741
2. R = 3kΩ
3. R1 =220kΩ
4. Diode
Operation:
The voltage drop against the each resistor is 3 volt.
So when the Vin = 0v or less than 3v the output of all op-amp are at
–Vsat . The silicon diodes protect the light emitting diodes against excessive reverse bias voltage.
When Vin is increased to a value 3v to 6v, only the output of op-amp#1 goes positive to light which indicate “Very Low”.
When Vin is increased to a value 3v and 6v, the output of op-amp#1 and op-amp#2 are at +Vsat and goes positive to light which indicate “Low”.
When Vin is increased to a value 6v and 9v, the output of op-amp#1, op-amp#2 and op-amp#3 are at +Vsat and goes positive to light which indicate “Medium”.
Similarly, when Vin increased to 12v or higher, the output of all op-amps are at +Vsat and all op-amps output goes positive to emit light of all LEDs which indicate “Full” .
Continue Reading here[...]
The top four LEDs indicates the battery voltage is high. Sequentially the lower level indicates the battery voltage is low and bottom four LEDs indicates very low voltage of the battery. So, if the battery voltage continues to decline then LEDs will die in sequence from top to bottom. In this circuit 1mA current is adjusted for reference voltage. Vcc is divided by the total number of resistor for finding the value of resistor R. On the other hand, the resistor value of R1 is calculated by the equation,
Component:1. Op-amp IC 741
2. R = 3kΩ
3. R1 =220kΩ
4. Diode
Operation:
The voltage drop against the each resistor is 3 volt.
So when the Vin = 0v or less than 3v the output of all op-amp are at
–Vsat . The silicon diodes protect the light emitting diodes against excessive reverse bias voltage.
When Vin is increased to a value 3v to 6v, only the output of op-amp#1 goes positive to light which indicate “Very Low”.
When Vin is increased to a value 3v and 6v, the output of op-amp#1 and op-amp#2 are at +Vsat and goes positive to light which indicate “Low”.
When Vin is increased to a value 6v and 9v, the output of op-amp#1, op-amp#2 and op-amp#3 are at +Vsat and goes positive to light which indicate “Medium”.
Similarly, when Vin increased to 12v or higher, the output of all op-amps are at +Vsat and all op-amps output goes positive to emit light of all LEDs which indicate “Full” .
Tuesday, October 9, 2012
Monday, September 17, 2012
Ceiling Fan Regulator - Motor Speed Control Circuit Diagram
This is a simple ceiling fan regulator circuit diagram. It is used to control the speed of a ceiling fan. In the other words it is an AC motor speed controller circuit, as because it's control the speed of a AC motor(Ceiling Fan). This ceiling fan regulator circuit built with few numbers of parts. The circuit mainly based on Z0607 TRIAC. This is a low power AC semiconductor device. Generally which is used to controlling speed of low power ac motor speed.
Circuit Diagram of Ceiling Fan Regulator :
In this ceiling fan regulator circuit, R1=500KΩ is a variable resistor that is used to adjust the fan speed. Capacitor C1 2A104J is a Polyester film capacitor.
Pin Diagram of TRIAC(T1)- Z0607:
Pin Diagram of Variable Resistor R1:
Parts List Ceiling Fan Motor Speed Controller circuit:
T1 = Z0607 -TRIACD1 = DB3 C312 -DIAC
R1 = 500KΩ -Variable Resistor
R2 = 37KΩ -Resistor
C1 = 2A104J -Polyester film capacitor.
M1 = Single Phase AC Motor (Ceiling Fan)-220V,50Hz
Saturday, July 14, 2012
555 Timer Touch Activated Alarm Circuit Diagram
This is the circuit diagram of touch activated alarm system which still activated on load shedding. Alarm system will be activated when someone touch the “touch plate” which is called trigger. In this circuit the most updated part is automatic battery activator which is made by a relay. So don’t upset on load shedding you alarm system is activated. This circuit could be used at your home door, locker, vehicle or metal gate etc.
Monday, May 14, 2012
Automatic Emergency Light Circuit Diagram
This is the simple circuit of automatic emergency light. It is called dark dependent circuit. A 555 timer IC and LDR is used for this configuration. When light fall on the LDR, its resistance is decrease and in dark position its resistance is going high. Using these characteristics of LDR, automatic emergency light is made.
LDR is called Light Dependent Resistor. Its resistance is inversely proportional to the falling light on its surface. In dark, its resistance is approximately 7k to 10k. When light fall on its surface, its resistance is decrease to less than 1k. In the circuit, a voltage dividerarrangement circuit is used here with LDR and 10K variable resistor.
When light fall on the surface of LDR, the resistance decrease to 1k. So the voltage of the timer pin-6 is greater than 2/3 of +Vcc. For this reason the output pin-3 goes low. The base voltage of transistor BC547 is less than 0.75 volt. The transistor is OFF state. So the light is OFF.
In dark position the LDR resistance increase is high so the voltage of the trigger pin-2 decrease to less than 1/3 of +Vcc. The output pin-3 goes high so the base voltage of the transistor BC547 is greater than 0.75 volt. The transistor is ON state. So the light is ON and it emits light.
Wednesday, January 18, 2012
Dual Voltage Power Supply 12 Volt
This is the simple circuit diagram of Dual Voltage Power Supply. It is used for Misc… application. This circuit is called regulated power supply. For this reason the main component of this circuit is Regulator IC. It also needs few components to built. The regulator 7812 is the positive voltage regulator and 7912 is the negative voltage regulator.
It regulates voltage from 24Volt to 12 Volt (DC). The transformer input is 110Volt to 220Volt (AC) and the output must be between 12Volt to 24Volt (AC) and current must be 500mA. In this circuit some capacitors are used as a filter for removing repole.
Sunday, October 30, 2011
Simple AM Transmitter Circuit
AM transmitter circuit that can transmit your audios to your backyard.This circuit is designed with limited the power output to match the FCC regulations and still produces enough amplitude modulation of voice in the medium wave band to satisfy your personal needs. You will love this.
These components can be easily obtained from your old medium wave radio. Q1 is provided with regenerative feedback by connecting the base and collector of Q1 to opposite ends of the tank circuit. C2 ,the 1nF capacitance , couples signals from the base to the top of L1, and C4 the 100pF capacitance ensures that the oscillation is transfered from collector, to the emitter, and through the internal base emitter resistance of the transistor Q2 (BC 109) , back to the base again.
The resistor R7 has a vital part in this circuit. It ensures that the oscillation will not be shunted to ground trough the very low value internal emitter resistance, re of Q1(BC 109), and also increases the input impedance such that the modulation signal will not be shunted to ground.
Q2 is wired as a common emitter RF amplifier, C5 decouples the emitter resistance and unleashes full gain of this stage. The microphone can be electret condenser microphone and the amount of AM modulation can be adjusted by the 4.7 K variable resistanceR5.
Tuesday, October 25, 2011
SIMPLE SWITCH TIME DELAY CIRCUIT DIAGRAM
SIMPLE SWITCH TIME DELAY CIRCUIT DIAGRAM
This Switch On Time Delay circuit should work with most any 12 volt DC relay that has a coil resistance of 75 ohms or more. The 10K resistor connected across the supply provides a discharge path for the capacitor when power is turned off and is not needed if the power supply already has a bleeder resistor.The circuit that takes advantage of the emitter/base breakdown voltage of an ordinary bi-polar transistor. The reverse connected emitter/base junction of a 2N3904 transistor is used as an 8 volt zener diode which creates a higher turn-on voltage for the Darlington connected transistor pair. Most any bi-polar transistor may be used, but the zener voltage will vary from about 6 to 9 volts depending on the particular transistor used. Time delay is roughly 7 seconds using a 47K resistor and 100uF capacitor and can be reduced by reducing the R or C values. Longer delays can be obtained with a larger capacitor, the timing resistor probably shouldn't be increased past 47K.
Monday, October 10, 2011
SIMPLE SWITCH-OFF TIME DELAY SCHEMATIC DIAGRAM
SIMPLE SWITCH-OFF TIME DELAY SCHEMATIC DIAGRAM
The two circuits di atas illustrate opening a relay contact a short time after the ignition or ligh switch is turned off. The capacitor is charged and the relay is closed when the voltage at the diode anode rises to 12 volts. The circuit on the left is a common collector or emitter follower and has the advantage of one less part since a resistor is not needed in series with the transistor base. However the voltage across the relay coil will be two diode drops less than the supply voltage, or about 11 volts for a 12.5 volt input. The common emitter configuration on the right offers the advantage of the full supply voltage across the load for most of the delay time, which makes the relay pull-in and drop-out voltages less of a concern but requires an extra resistor in series with transistor base. The common emitter (circuit on the right) is the better circuit since the series base resistor can be selected to obtain the desired delay time whereas the capacitor must be selected for the common collector (or an additional resistor used in parallel with the capacitor).
The time delay for the common emitter will be approximately 3 time constants or 3*R*C. The capacitor/resistor values can be worked out from the relay coil current and transistor gain. For example a 120 ohm relay coil will draw 100 mA at 12 volts and assumming a transistor gain of 30, the base current will be 100/30 = 3 mA. The voltage across the resistor will be the supply voltage minus two diode drops or 12-1.4 = 10.6. The resistor value will be the voltage/current = 10.6/0.003 = 3533 or about 3.6K. The capacitor value for a 15 second delay will be 15/3R = 1327 uF. We can use a standard 1000 uF capacitor and increase the resistor proportionally to get 15 seconds.
Saturday, October 8, 2011
SMOKE DETECTOR CIRCUIT USING LDR SCHEMATIC DIAGRAM
SMOKE DETECTOR CIRCUIT USING LDR SCHEMATIC DIAGRAM
When there is no smoke the light from the bulb will be directly falling on the LDR.The LDR resistance will be low and so the voltage across it (below .6V).The transistor will be OFF and nothing happens. When there is sufficient smoke to mask the light from falling on LDR, the LDR resistance increases and so do the voltage across it.Now the transistor will switch to ON.This gives power to the IC1 and it outputs 5V.This powers the tone generator IC2 to play a music.This music will be amplified by IC3 to drive the speaker.
The diode D1 and D2 in combination drops 1.4 V to give the rated voltage (3.5V ) to UM66 .UM 66 cannot withstand more than 4V.
AM Receiver Circuit Diagram Using ZN414 IC
A.M. Antenna coil and MW gang connected in parallel. One common point of this parallel circuit connected to the IC ZN414 pin number 2.
Another common point of that parallel circuit connected with two resistors (100kΩ, 1kΩ) in series. A capacitor is connected with the common point of resistors (100kΩ, 1kΩ). A capacitor is connected in series with base of the transistor and the pin number 1 of the ZN414.
One end of the 10kΩ resistor is connected with the collector point of the transistor BC549 and another end is connected with the power supply +Vcc.
And one end of the 100kΩ resistor is connected with the collector and another end connected with base. 105pF capacitor is connected between collector and ground. Pin 3 of IC ZN414 and emitter of the transistor is connected to the ground.
Required Instrument
- IC ZN 414.
- Capacitor(105pF×1,104pF×2,103pF×1)
- MW Gang
- Resistor(100kΩ×2,10kΩ×1,1kΩ×1,470Ω×1)
- AM antenna
- Transistor(BC549)
Friday, September 23, 2011
AM Transmitter Circuit Diagram Using 741 Op-amp
AM transmitter is a circuit which can transmit message signal to modulated signal. This circuit is designed with limited power and the required power supply of the transmitter circuit is 9 Volt.
The circuit has three parts that is an audio amplifier, radio frequency oscillator and modulator circuit. The frequency oscillator is built with 741 Op-amp and related components. The carrier signal frequency and its amplitude can be varied using variable resistor accordance with VR1 and VR2 respectively. C1 and C2 are the main components to generate the carrier frequency.
Another part of the circuit is an audio amplifier circuit. The audio amplifier is built with 741 Op-amp and related components. A microphone is used to convert the voice signal to the audio signal which is feed to the op-amp’s inverting terminal. This audio signal is amplified by the op-amp. The amplified audio signal is filtered using the capacitor C7. This output is feed to the modulator circuit.
The main part of the AM transmitter is modulator circuit which is built with the transistor BC109. The carrier signal is feed to the base of transistor and the message / audio signal is also feed to the emitter of the transistor.
Here the required modulated signal is taken from the collector of the transistor which is feed to the output antenna.
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