Ding Dong Bell circuit diagram

This is a ding dong bell circuit diagram.I have attached this circuit for my house.Even you can use this circuit as an sound generator.When we buy this circuit from the market we have to spend much money but now you can build this your self.Here I have used common Ic Ne 555 and you can operate this circuit with 9V power supply.




Note

# Build this circuit on a pcb

# use 9V power supply to power this circuit

# When you deal with 230V be careful

Night lamp Circuit diagram

This is a night lamp .This circuit operates with 3V power supply. Here I have used famous IC max660.Use a white LED to light up this.Use a pcb to build these circuit.

Fan controller with LM 741

This is fan controller circuit diagram.This circuit can operate the fan automatically.Here we have used supply from the transformer’s auxiliary 12V winding.we have used famous Ic LM 741 here

Simple Intercom Circuit diagram

This is a intercom circuit diagram.you can use this for your office or for your working place.Acoording to the changes of s1a and s1b You can use this as the reciever and the mic



Note

# Use screen wires Between these two circuits

Automatic Dresses Collector When Rain Comes

This is Little bit strange circuit.But I have used simple method.When the rain comes This circuit collects dresses automatically.So you don't want to collect dresses you yourself.Here I have used common Ic NE 555.Use a relay for the moter.

water tank Alarm to stop over flowing

This circuit is so simple concept.But by using this circuit you can prevent overflowing your water tank.After water touching sensors the circuit will give a sound.then you can switch off the mot er.




Note

# fix your circuit near by the water tank.Unless it will not work properly due to less power supply.

# This circuit operates with 9V power supply

water-triggered-alarm-system-with-555-timer

You can use this circuit for you water tank.then you can know before over flowing your tank.on the other hand you can use this circuit as a rain detector then you can know before rain comes.so I suppose this would be a so useful circuit for you

Thermostat

This is simple electronic thermostat using IC LM56.by using this one you can know whether the temperature of the equipment that you use is over heating or not.so this is very useful equipment to save your electrical equipments from over heating.





Two stable temperature trip points (VT1 and VT2) are created by dividing the LM56’s 1.250V internal voltage reference using 3 external resistors (R1, R2 and R3). There are two digital outputs for LM56 .Output1 becomes LOW when the temperature increases above T1 and goes HIGH when the temperature decreases below (T1±Hysteresis Temperature). In the same way, Output2 becomes LOW when the temperature goes above T2 and goes HIGH when the temperature goes below (T2±Hysteresis Temperature).


VT1 = 1.250V x (R1)/ (R1 + R2 + R3)
VT2 = 1.250V x (R1 + R2)/ (R1 + R2 + R3)
where:
(R1 + R2 + R3) = 27 k Ohms and
VT1 or T2 = [6.20 mV/degree Celsius x T] = 395 mV therefore:
R1 = VT1/ (1.25V) x 27 k Ohms
R2 = (VT2/ (1.25V) x 27 k Ohms) – R1
R3 = 27 k Ohms – R1 – R2

Water activated musical bell

This circuit gives a sound when water or conducting liquid touches with the sensors which are provided (A,B).by using this circuit you can get lots of advantages as an example you can attach this one for your water tank and when it over flows you can know it before be creative then you can make lots of things with this.





Notes.

* Two insulated aluminum wires can be used as the sensor.
* The IC1 must be mounted on an IC holder.
* The speaker can be a 8 Ohm, ½ W tweeter.
* Assemble the circuit on a good quality PCB or common board.

Door Bell circuit using UM 66 IC

Here is a simple and east to build doorbell circuit using IC UM 66.The details of UM 66 is given in the older post “Melody Generator using UM 66″.This is a slight modification of that circuit.In the previous circuit you have to keep the switch pressed for making the IC play the full music.




Here if once the push button is pressed C1 is charged and the transistor Q2 will keep the IC playing the music till it ends.The time for the IC to play depends on discharging time of C1 which can be set by R1.Set R1 to select your time ,whether full tone or a part in one press.Transistor Q2 drives the speaker.

Notes

* Do not give more than 4.5 V to UM 66.
* POT R2 is not necessary and can be bye passed .But if included you can set the loudness.

Super Sensitive Intruder Alarm

Here is the circuit diagram of an ultra sensitive intruder alarm.The shadow of an intruder passing few meters nearby the circuit is enough to trigger the alarm.






Here IC2 uA 741 is wired as a sensitive comparator ,whose set point is set by R6 &R7.The voltage divide by LDR and R9 is given at non inverting pin of IC2.At standby mode these two voltages are set equal by adjusting R9.Now the out put (pin6) of comparator will be high.Transistor Q1 will be off.The voltage at trigger pin of IC1 will be positive and there will be no alarm.When there is an intruder near the LDR the shadow causes its resistance to increase.Now the voltages at the inputs of comparator will be different and the out put of IC2 will be low.This makes Q1 on.This makes a negative going pulse to trigger the IC1 which is wired as a monostable multivibrator.The out put of IC1 will be amplified by Q2 (SL 100) to produce alarm.



Notes

* To setup the alarm ,power up the circuit and adjust R9 so that LED D1 goes off.
* The LDR can be housed in a dark tube to increase sensitivity.
* The sensitivity is very important here.If you cannot adjust the required sensitivity properly, use one LOW resistance (~1K ) POT in series with R9 for fine adjustment.

Fridge Door “Open!” Alarm

This circuit produces an audible alarm when fridge is left open for a preset time.This versatile alarm is based on two 555 timer IC’s.Both ICs are wired as astable Multivibrators.






An LDR is connected in parallel to the timing capacitorC1 of IC 1.When door is completely close there will be no light inside the fridge and LDR offers high resistance keeping R1 fully charged.When door is left open ,the lamp inside the fridge will remain glown ,LDR will be illuminated,and its resistance falls.This makesC1 stop charging and starts to discharge ( In simple words ,this is because at low resistance LDR bye passes much of the current in the parrallel path and capacitor gets less current).Now IC 1 starts slightly oscillating and after a preset time of 25 ( time T1) seconds its output goes high.This out put makes the Ic 2 to produce oscillations and results in a beeping sound for next 20(time T2) seconds and cycle is repeated till door is closed.



Notes .

Assemble the circuit on a good quality PCB .Time T1 & T2 can be adjusted by varying C1, C2, R1, R4 etc (Refer data sheet of 555).Place the LDR close enough to the lamp inside the fridge.





Parts List.

R1_____________10K 1/4W Resistance
R3_____________2.2 M 1/4W Resistance
R4_____________1M 1/4W Resistance

C1_____________10µF 25V Electrolytic Capacitance
C2_____________100nF 63V Polyester Capacitance

D1____________ 1N4001 Diode

IC1,IC2_________NE 555 Timer ICs

BZ1___________ Piezo Buzzer

B1____________ 3V Cell

Cat repeller circuit

With this cool cat repeller circuit you could chase the cats off from any where you want.In fact, I designed this circuit to chase my cat from my computer table.Most of the animals like cats respond violently to ultrasonic sound and in fact it’s the best way to chase them off.This principle is employed in this circuit.





The circuit here is nothing but an astable multi vibrator wired around NE555 (IC1).The produces an ultrasonic sound in the range 15-20Khz.The NE 555 is enough to drive a small piezo buzzer and no amplification stages are needed.The POT R2 can be used to adjust the frequency of sound.




Notes.

* The circuit can be powered from a 9V battery or the power can be tapped from your computer SMPS.
* The circuit can be assembled on a general purpose PCB.

Mosquito repeller power saver

Almost all liquidator type mosquito repellers are rated 5Watts.It is a pretty energy consuming game when these repellers are operated through out the night.Even though these liquidators are switched ON and OFF in discrete intervals there will be no considerable loss in the effectiveness,and more over there will be a great saving of energy.Then why can’t we do that and that’s why I designed this circuit.






The circuit is nothing but an astable multivibrator designed of IC NE 555 (IC1) operates in a frequency determined by the values of R1 and C2.When the power is switched on the out put of the IC goes high .This makes Q1 to conducts and the relay connects the mains supply to the repeller plugged in the socket shown.After the set time theout put of the IC goes low and now the repeller is removed from mains by the relay.This cycle repeats and the repeller will be switched On and OFF in frequent intervals,saving a lot of power.Diodes D2,D3 forms a half wave rectifier with C1 as the filter,supplies the circuit with power .




Notes.

* Assemble the circuit on a good quality common board or PCB.
* The intervals of ON and OFF can be adjusted by varying Preset R1.
* Some parts of the circuit are live with potential shock hazard.Be carefu

Water level alarm circuit

Here is a simple water level alarm circuit that will produce an audible alarm when the water level reaches a preset level.The circuit can be powered of a 3V battery and is very handy to use.





The circuit is based on an astable multivibrator wired around IC1 (NE 555).The operating frequency of the astable multivibrator here will depend on capacitor C1, resistances R1,R2 and the resistance across the probes A&B.When there is no water up to the probes,they will be open and so the multivibrator will not produce oscillations and the buzzer will not beep.When there is water up to the level of probes,some current will pass through the water,the circuit will be closed to some extend,and the IC will start producing oscillations in a frequency proportional to the value of C1,R1,R2 and the resistance of water across the probes.The buzzer will beep to indicate the presence of water up to the level of the sensing probes.




Notes.

* The circuit can be powered of a 3V battery.
* Assemble the circuit on a good quality PCB or common board.
* The probes can be made of two insulated copper Aluminiun wires.
* Place the probes at the position where you have to sense the leve

Door bell circuit using NE555

The main part of this doorbell circuit are two NE555 timer ICs.When some one presses switch S1 momentarily ,the loud speaker sounds a bell tone as long as the time period of the monostable multivibrator built around IC1.







When the switch S1 pressed, IC1 is triggered at its pin 2 and output pin 3 goes high for a time period previously set by the values of POT R4 and POT R5.When the output ofIC1 goes high it resets IC2 and it starts to oscillate to make a bell sound through the speaker.The IC2 is configured as an astable multivibrator whose oscillation frequency can be varied with the help of POT R5.By adjusting the values of R4 & R5, modifications on the tone are possible.



Notes.

* The circuit has to assembled on a good quality PCB or common board.
* The IC1 & IC2 has to be mounted on IC holders.
* Power the circuit from a 9V battery or 9V DC power supply.
* Switch S1 is push button switch.

Plant moisture level monitor

Here is a simple circuit that will give a visual indication when the soil water level inside your flower pot goes low below a certain limit.





The U1C and associated components are wired as an oscillator producing a 2KHz square wave. This square wave is given to one gate input of U1D via a variable potential divider former by R1 and R2.When the resistance across the probes A and B are low that is when soil moisture level is high, the C2 will divert the square wave to ground. The output of U1D will be high. The U1 A inverts this high state to low and so the IC U1B is blocked from producing oscillations. The LED will remain OFF. When there is no moisture across the probes, the C2 cannot bypass the 2KHz signal to the ground and it appears at the gate input of U1D.The output of U1D goes low, and it is inverted to high by U1A.The oscillator wired around U1B is activated and it starts oscillating. These oscillations are amplified by Q1 to drive the LED and LED starts pulsating as an indication of low moisture. Since square wave is used there won’t be any oxidation on the probes. The resistor R7 limits the current through LED and ensures a longer battery life.



Notes.

* Power the circuit from a 3V battery.
* Two metal wires 10 cm long and 5cm apart driven into the soil will do the job for probes.
* The probes are to be connected at the terminals A and B shown in circuit.
* Capacitors C1 and C2 must be polyester type.
* The IC U1 is a quad two input Schmitt NAND IC 4093.
* The sensitivity can be adjusted by varying the preset R2.
* Mount the IC on a holder.

Battery operated heater

Here is a simple heater circuit that can be operated from a 12V battery. The first part of the circuit is an a stable multivibrator build around the two transistors Q1 and Q2 .The ON time of transistor Q2 is set to 0.5 S. The ON time of transistor Q1 can be varied by using the POT R2.The output pulses at the collector of Q2 is used to drive the Darlington power transistor Q3(TIP122).The transistor Q3 drives the heating elements L1 to L3.The net heat produced can be varied by selecting the desired combination of heating elements at the output circuit sing switches S1 and S2.The net heat can be also varied by varying the duty cycle of the triggering pulse using POT R2.





Notes.

* The circuit can be assembled on a general purpose PCB.
* The transistor Q3 must be fitted with a heat sink.
* The elements L1 to L3 can be 10W heating coils.
* The switches S1 and S2 must be able to withstand at least 5A.
* The circuit can be powered from a 12V battery.
* The LED D1 gives a visual indication of the duty cycle of the circuit.

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 DC fan depending on the temperature.A thermistor (R1) is used to sense the temperature. When the temperature increases the base current of Q1 (BC 547) increases which in turn decreases the collector voltage of the same transistor. Since the collector of Q1 is coupled to the base of Q2 (BD 140), the decrease in collector voltage of Q1 forward biases the Q2 more and so do the speed of the motor. Also, the brightness of the LED will be proportional to the speed of the motor.








Notes.

* The R1 can be a 15K @ 20°C ,N.T.C thermistor.
* The M1 can be a 12V,700mA fan motor.
* The capacitor C1 must be rated 25V.
* The circuit can be powered from a 12V PP3 battery or 12V DC power supply.
* Assemble the circuit on a good quality PCB or common board.

Automatic Speed Controller for fans & Coolers

During summer nights, the temperature is initially quite high. As time passes, the temperature starts dropping. Also, after a person falls asleep, the metabolic rate of one’s body decreases. Thus, initially the fan/cooler needs to be run at full speed. As time passes, one has to get up again and again to adjust the speed of the fan or the cooler.The device presented here makes the fan run at full speed for a predetermined time. The speed is decreased to medium after some time, and to slow later on. After a period of about eight hours, the fan/cooler is switched off.Fig. 1 shows the circuit diagram of the system. IC1 (555) is used as an astable multivibrator to generate clock pulses. The pulses are fed to decade dividers/counters formed by IC2 and IC3. These ICs act as divide-by-10 and divide-by-9 counters, respectively. The values of capacitor C1 and resistors R1 and R2 are so adjusted that the final output of IC3 goes high after about eight hours.The first two outputs of IC3 (Q0 and Q1) are connected (ORed) via diodes D1 and D2 to the base of transistor T1.




It can be seen that initially the fan shall get AC supply directly, and so it shall run at top speed. When output Q2 becomes high and Q1 becomes low, relay RL1 is turned ‘off’ and relay RL2 is switched ‘on’. The fan gets AC through a resistance and its speed drops to medium. This continues until output Q4 is high. When Q4 goes low and Q5 goes high, relay RL2 is switched ‘off’ and relay RL3 is activated. The fan now runs at low speed.Throughout the process, pin 11 of the IC is low, so T4 is cut off, thus keeping T5 in saturation and RL4 ‘on’. At the end of the cycle, when pin 11 (Q9) becomes high, T4 gets saturated and T5 is cut off. RL4 is switched ‘off’, thus switching ‘off’ the fan/cooler.Using the circuit described above, the fan shall run at high speed for a comparatively lesser time when either of Q0 or Q1 output is high. At medium speed, it will run for a moderate time period when any of three outputs Q2 through Q4 is high, while at low speed, it will run for a much longer time period when any of the four outputs Q5 through Q8 is high.If one wishes, one can make the fan run at the three speeds for an equal amount of time by connecting three decimal decoded outputs of IC3 to each of the transistors T1 to T3. One can also get more than three speeds by using an additional relay, transistor, and associated components, and connecting one or more outputs of IC3 to it.