Friday, August 31, 2012

3 Band Tone Control Circuit Using Op-Amp LF351

Here is the circuit of 3 band tone control using a single op-amp IC and few components. The IC used here is LF 351 which is a wide bandwidth single JFET operational amplifier.
Op-Amp 3 band tone control circuit
The high input impedance of the IC makes this circuit compatible with most of the audio signal sources. The op-amp is wired as an inverting amplifier. The input signal is fed to the inverting input of the opamp via the filter network. The filter network can produce a +/- 20 dB enhancement or cut on the three frequency bands 50Hz,1KHz and 10KHz.POTs R1, R2 and R3 can be used for adjusting the gain of the different bands


Detail download here

Wednesday, August 29, 2012

NE555 12VDC Fluorescent Lamp Driver Circuit

This is a circuit of 12VDC fluorescent lamp Driver for those who look for Fluorescent lamp driver using ordinary transformers. The transformer used is a step-down transformers from 120 to 6V in reverse, so that with primary voltage 12V could produce 350V for output. This voltage is used to turn on the fluorescent lamp without heating the filament.
NE555 12VDC Fluorescent Lamp Driver Circuit
The IC1 TLC 555 is wired as an astable multivibrator for producing the necessary oscillations.The MOSFET Q1 is used to amplify the oscillations produced by the IC1.The out put of MOSFET is connected to the primary of the step up transformer to produce a ~350 V AC for driving the florescent lamp.

Note:
  • Take note that heat sink should be used on Q1, and be careful of the electric shock from the output voltage!
  • For T1, use a 10W ,230V to10V step down transformer in the inverted configuration.That is 10V winding must be connected to the MOSFET side and 240V winding must be connected to florescent lamp side.
List Component of 12VDC Fluorescent Lamp Driver
C1    : 100uF/25V 
C2,C3 : 0.01/25V Ceramic Capacitor
C4    : 0.01/1kV Ceramic  Capacitor
R1    : 1K
R2    : 2.7K
Q1    : IRF510 MOSFET
U1    : NE555 Timer IC
T1    : see note
LAMP  : 4W Fluorescent Lamp
Detail download here

Tuesday, August 28, 2012

IRF530 Fet Flasher Circuit

This is a simple fet flasher circuit that can be used for flashing 12V lamps especially that is used on automobiles.The flasher circuit is based on transistor BC557 and MOSFET IRF530 where the Q2 provides the necessary drive for the lamp.Any number of bulbs can be flashed using this circuit provided that the total load must not exceed 42 Watts. Circuit of this kind are particularly suited for road, traffic and yard alerts and in all cases where mains supply is not available but a powerful flashing light is yet necessary
IRF530 Fet Flasher Circuit
Note:
Flashing frequency can be varied within a limited range by changing C1 value.

List Componet
R1 : 6K8
R2 : 220K
R3 : 22K
C1 : 100µF/25V
C2 : 10µF/25V
D1 : 1N4002
Q1 : BC557
Q2 : IRF530
LP1: 12V/21W Car Filament Bulb 
SW1: SPST Switch (3 Amp minimum)

This circuit from:   www.redcircuits.com
Detail download here

Saturday, August 25, 2012

3 Volt LED Flasher Using 2 Transistor

Applications due to its simplicity and versatility. This Flasher circuit is great for beginners! If you build it, it will flash. And you can easily change the on-time and flash rate.

The two resistors on the base of the PNP set a threshold voltage and when power is applied the capacitor begins charging toward this voltage. When the capacitor voltage is high enough the two transistors begin to conduct. The current flow causes the voltage across the circuit to drop slightly and this drop causes a drop in the threshold voltage. The lower threshold voltage causes even more current and this positive feedback causes the circuit to rapidly turn on. It stays on until the capacitor discharges at which point a reverse process causes the circuit to suddenly switch off.
3Volt  LED Flasher Circuit
Note:
  • Flashing frequency can be varied by changing R1 value in the 1M - 4M7 range.
  • This circuit is very efficient when driving a small 3.2V incandescent lamp. In this case omit the LED and R3, connecting the bulb across Q2 Collector and positive supply, further reducing parts counting.
  • Maximum current drawing of the bulb type used should not exceed 100mA.
  • In order to facilitate oscillation when a bulb is driven, R2 value should be lowered to 82R or 68R.
Lis Componet

R1  : 1M   1/4W Resistor
R2  : 100R  1/4W Resistor
R3  : 22R   1/4W Resistor
C1  : 1µF/63V 
D1  : LED  
Q1  : 2N3906  PNP Transistor
Q2  : 2N3904  NPN Transistor
SW1 : SPST Switch
B1  : 3V (Two 1.5V AA or AAA battery) 
 
 
Detail download here

Op-Amp 741 Guitar Preamplifier Circuit

This preamplifier circuit suitable for high impedance type electric guitar.The circuit is based on a UA 741 op-amp. The UA741 is wired as a non-inverting amplifier.The POT R1 can be used as a volume controller.The POT R6 can be used as tone controller.The switch S1 is used to produce “brilliant” or “soft” tonal effects
Op-Amp 741 Guitar Preamplifier Circuit
Op-Amp 741 Pinout

This circuit from: www.circuitstoday.com
Detail download here

Thursday, August 23, 2012

On-Off Touch Switch Using IC CD4011 Circuit

This is a circuit of electrnic on-off Touch switch controller using IC CD 4011 that is connected as a FLIP-FLOP. He is simple in the manufacture and the materials that use they exist everywhere. This based in the known CD 4011, which drives a relay of which the contacts play the role of switch. The metal surfaces can have what form we want, but it should they are clean and near in the circuit. In order to it changes situation it suffices touch soft somebody from the two plates.
On-Off Touch Switch Using IC CD4011  Circuit
 CD4011 (IC FLIP-FLOP) Pinnning
This high sensitivity of the circuit makes the touch switch  operation possible. The two gates are held at logic state «1» continuously by means of the two resistors R1 and R3 that connect them to the positive supply rail. These resistors have a very large resistance of 10 Mohm. If we now touch a set of contacts the skin resistance closes the circuit between the corresponding gate and the negative supply rail. The skin resistance for small areas of the skin is normally much lower than 10 Mohm and the gate is effectively brought to logic condition «0» which makes the FLIP-FLOP change state. For any given state of the FLIP-FLOP touching the corresponding set of contacts will make the circuit to reverse its state of balance and in effect toggle the switch. As a switch is used a relay driven by a transistor which is driven from the out put of the FLIP-FLOP.

List Component Of On-Off Touch Switch Circuit
R1  : 10MOhm 1/4 W
R2  : 10MOhm 1/4 W
R3  : 1KOhm 1/4 W
D1  : Led red
D2  : 1N4148 diode
TR1 : BC558 PNP Transistor – BC327
IC1 : CD4011 CMOS IC
RL1 : 12V relay rated at 250 V / 2A 
Detail download here

Simple 220V AC Blinking LED Using Diac

needed a blingking led for a certain signaling. Voltage was 220V. So I decided to make a simple circuit, consisted of a LED diode, two capacitors, two resistors, a diac and a diode.
Simple 220V AC Blinking LED Circuit
Activity of the circuit is extraordinarily simple. The capacitor charges by the diode and the resistor. When the voltage on the capacitor achieves 30V the diac "releases" the electrical tension and the capacitor empties thorough the diac, LED blinks. Time base is dependent from the capacitor and the resistor, which is in series with diode 1N4007. Capacitor must be at least for 40V.
Detail download here

Wednesday, August 22, 2012

FM Wireless Microphone Circuit Using Single Transistor

This FM Wireless Microphone circuit huses only a single transistor with few additional passive components and has range over 30-50m (under good conditions). This FM transmitter is very compact and need only a single cell 1.5Volt battery, even works on 1.2V rechargeable battery.
Simple FM Wireless Microphone Circuit
 The inductance L is the critical part and should be handmade. Use an AWG24 (0.5mm) enameled copper wire and make 2-4 loose turns with about 4-5mm diameter. Try to loosen or tighten the coil, or trim the variable capacitor, and try to receive the signal on around 90MHz. Don’t forget to tighten the coil using a glue to fix the coil, avoiding mechanical deformation that change its inductance value.
Detail download here

LDR Light / Dark Activated Relay Switch

This is a simple Light / Dark Activated Relay  circuit with the base of the LDR. The voltage divider has two resistors. The first is the 100K potentiometer plus the protective 1K resistor. the second resistor is the LDR.
LDR Light / Dark Activated Relay Circuit
As light falls on the surface of the LDR, the LDR changes it's resistance. The more the light, the less the resistance of the LDR, the less the resistance, the less the voltage drop across it. The less the light, the more the resistance and thus the more the voltage drop across it.

As the voltage drop increases, so does the VB of the 2N2222 transistor and therefore the ICE increases accordingly, until the time that the current is enough to actuate the relay.

The amount of light needed to actuate the relay can be changed by changing the 100K potentiometer. Basically, any change to the potentiometer will have an effect to the voltage drop of the LDR, as they are both members of the voltage divider described above.

The 1N4001 diode is used to eliminate any back voltage when the relay is disarmed. It is very important to have this diode because without it, the transistor may be damaged.
Detail download here

Touch Activated Light circuit using Mosfet IRF510

Here is a circuits light a 12V/20 watt lamp when the contacts are touched and the skin resistance is about 2 Megs or less. This circuit uses a power MOSFET (IRF510) which turns on when the voltage between the source and gate is around 6 volts. The gate of the MOSFET draws no current so the voltage on the gate will be half the supply voltage or 6 volts when the resistance across the touch contacts is equal to the fixed resistance (2 Megs) between the source and gate.

Touch Activated Light circuit using Mosfet IRF510
Mosfet IRF510 Pi
Absolute Maximum Rating Of IRF510
Drain to Source Voltage        : 100 V
Drain to Gate Voltage          : 100 V
Continuous Drain Current (ID)  : 5.6 A
Pulsed Drain Current (IDM)     : 20 A
Gate to Source Voltage (VGS)   : ±20 V
Maximum Power Dissipation (PD) : 43 W 
Detail download here

22 Watt Car Subwoofer Amplifier

This Subwoofer circuit is intended to be connected to an existing car stereo amplifier, adding the often required extra "punch" to the music by driving a subwoofer. As very low frequencies are omnidirectional, a single amplifier is necessary to drive this dedicated loudspeaker.

The power amplifier used is a BTL TDA1516BQ IC made by Philips requiring a very low parts count and capable of delivering about 22W into a 4 Ohm load at the standard car battery voltage of 14.4V. 
22 Watt Car Subwoofer Amplifier Circuit
 The stereo signals coming from the line outputs of the car radio amplifier are mixed at the input and, after the Level Control, the signal enters the buffer IC1A and can be phase reversed by means of SW1. This control can be useful to allow the subwoofer to be in phase with the loudspeakers of the existing car radio. Then, a 12dB/octave variable frequency Low Pass filter built around IC1B, Q1 and related components follows, allowing to adjust precisely the low pass frequency from 70 to 150Hz.

Q2, R17 and C9 form a simple dc voltage stabilizer for the input and filter circuitry, useful to avoid positive rail interaction from the power amplifier to low level sections.

List Componet  Of Car Subwoofer Amplifier 
P1           : 10K  Potentiometer
P2           : 22K  Dual Potentiometer
R1,R4        : 1K  1/4W Resistors
R2,R3,R5,R6  : 10K 1/4W Resistors
R7,R8        : 100K 1/4W Resistors
R9,R10,R13   : 47K  1/4W Resistors
R11,R12      : 15K  1/4W Resistors
R14,R15,R17  : 47K  1/4W Resistors
R16          : 6K8  1/4W Resistor
R18          : 1K5  1/4W Resistor
C1,C2,C3,C6  : 4µ7/25V
C4,C5        : 68nF Polyester Capacitors
C7           : 33nF Polyester Capacitor
C8,C9        : 220µF/25V
C10          : 470nF Polyester Capacitor
C11          : 100nF Polyester Capacitor
C12          : 2200µF/25V
D1           : LED  
Q1,Q2        : BC547 NPN Transistors
IC1          : TL072 Op-Amp
IC2          : TDA1516BQ 
SW1          : DPDT toggle or slide Switch
SW2          : SPST toggle or slide Switch 
SPKR         : 4 Ohm Woofer or two 8 Ohm Woofers wired in parallel


Circuit From: www.redcircuits.com
Detail download here

Monday, August 20, 2012

STK672-110 Full|Half Stepper Motor Controller

The STK672-110 chip has no microstepping mode and also has some less capabilities than the 080, yet it is very flexible and compact for full and half wave stepper motor applications.
STK672-110 Full|Half Stepper Motor Controller Circuit

S1 controls the rotation direction of the motor. The reset circuit (R1-D1-C3) is as described by the manufacturer of the chip. You can use this input (Pin 6) for making resets other ways, like for example if you plan to control the chip with a microcontroller. In this case, you need to know that you must make a 10msec reset, every time that the chip is powered for the first time.

From the "MODE" input you control the type of stepper control. In this circuit, the chip connected for half-step. If you change the MODE input from +5 to GND, the circuit will work as a full step motor controller.

As for the coils of the motor, you need to connect the common wires of the coils (can be 1 or 2 on a unipolar motor) to the "C" connector, and the other 4 wires to the connectors "1" through "4". Usually, unipolar motors with 5 wires have the outputs in "1-2-C-3-4" row, and with 6 wires goes like "1-2-C-3-4-C" or "C-1-2-C-3-4" but this is can change! This is NOT always the same. You can go with trial and error or by measuring the coils of the motor to find the correct order. Do not forget the C4 capacitor!

About C4: In the Bill Of Materials underneath, this capacitor as 220uF 100V... Just playing safe. The chip can handle up to 50V, but this does not mean that cannot handle less. So, if your motor is like 3.3 volts or 5 volts, then a 100V capacitor is just too much. Get a 220uF 16V instead. Just do not be too close, for example, if your motor is powered with 12 Volts, go to 220uF 25 volts better. Electrolytic capacitors make a rather unpleasant noise when they explode.

For more details about STK672-110  stepper motor controller circuit please visit  pcbheaven.com
Detail download here

Thursday, August 16, 2012

12V to 220V Inverter Using 2n3055 Transistor

Here is a simple 12 V to 220V inverter for using a small aplications in the absence of mains supply. It uses eight transistors and a few resistors and capacitors. Transistors T1 and T2 form an astable multivibrator that produces 50Hz signal. The complementary outputs from the collectors of transistors T1 and T2 are fed to pnp Darlington driver stages formed by transistor pairs T3-T5 and T4-T6. The outputs from the drivers are fed to transistors 2N3055 (T7 and T8) connected for push-pull operation.
Circuit Of 12V to 220V Inverter Using 2n3055 Transistor

A 230V AC primary to 12VCT/4.5A secondary transformer is used. The centre-tapped terminal of the secondary of the transformer is connected to the battery (12V, 7Ah), while the other two terminals of the secondary are connected to the collectors of power transistors T7 and T8, respectively.

When you power the circuit using switch S1, transformer X1 produces 230V AC at its primary terminal. This voltage can be used to heat your soldering iron. Assemble the circuit on a general purpose PCB and house in a suitable cabinet. Connect the battery and transformer with suitable current-carrying wires. On the front panel of the box, fit power switch S1 and a 3-pin socket for connecting the soldering iron.

Note:
Use suitable heat-sinks for transistors T5 through T8.
Detail download here

Touch Activated 12V Lamp Circuit Using Transistor

This circuit uses three bipolar transistors to accomplish the Same result with the touch contact referenced to the negative or ground end of the supply. The 12volt 20W lamp will be turn on when the contacts are touched with skin resistance about 2M or less. This circuits are available also for other applications, for additional current the lamp could be replace with a 12V relay and diode across the coil.

Touch Activated 12V Lamp Circuit
Since the base of a bipolar transistor draws current and the current gain is usually Less than 200, three transistors are needed to raise the microamp current levels through the touch contacts to a couple amps needed by the light.
Detail download here

Wednesday, August 15, 2012

STK465 - 30 watt Stereo Power Amplifier Circuit

Completed STK465 is an amplifier of acoustic frequencies that offers qualitative output, using minimal exterior elements. Substantially he is one of big completed force. When it functions with tendency 56V then the tendency will be ± 28V as for the ground. With this recommended tendency of catering, the attributed force is 30 WRMS in charge 8 Ohm.
STK465 - 30 watt Stereo Power Amplifier Circuit
The STK465 Amplifier  circuit is stereo and has two channels of amplifier in a nutshell. It is a formal designing that develops positively all the particularities completing. The amplifier can be supplied from a line of double polarity. Still it can function under a wide region of tendencies (±10V as ±28V). The requirements of current depend from the force of expense and it can they begin from 120mA up to 1A. It is very important the catering to be sufficiently unharnessing, so that is avoided imports of annoying noises.
Detail download here

FM Wireless Microphone Transmitter

This FM wireless microphone transmitter can transmit speech over a short range. It can be used as a simple cordless microphone. This circuit has good frequency stability and has range over 1 Km (under good conditions). This project features RF amplifier buffer (10dB gain), an AF preamplifier to boost the modulation and good microphone sensitivity. You can use it for guitars and remote control system.
FM Wireless Microphone Transmitter
This circuit quite simple to build. The two BC547 transistors can be replaced with any small-signal NPN transistor, such as the 2N2222. L1 is 3.25 turns in spiral form and is an integral part of the PCB foil pattern. The final stage is a BC557 PNP general purpose device. If you use different devices then you should select the 1M0 resistor for 5-volts DC at the collector of the first transistor. Select the 47K resistor for 3 – 4 volts on the collector of the third transistor.
Detail download here

Tuesday, August 14, 2012

3-Input Mic Preamplifier Circuit Using Op-Amp LM348

This is a 3-input mic preamplifier circuit using IC LM348. The LM348 is a high gain, internally compensated quad operational amplifier with a class AB output stage. The IC has very low input supply current and operates from a dual power supply.
Op-Amp 3-Input Mic Preamplifier Circuit
Op-Amp LM348 Pinout
Out of the four op-amps inside the IC LM348, IC1a, IC1b and IC1c are wired as non inverting amplifiers and they serve as the input amplifiers for the corresponding mic channels. The output of these three amplifiers are tied together and connected to the inverting input of the IC1a which is wired as an inverting amplifier. IC1a mixes the signals from each channel and also works as the output stage.

This circuit from: www.circuitstoday.com 
Detail download here

Simple Touch Switch Circuit Using Transistor

A simple electronic touch switch can be constructed using this circuit diagram . This electronic touch switch is based on two transistors an can activate a relay , when the touch sensor is pressed .
Simple Touch Switch Circuit Using Transistor

The touch sensor can be constructed using a small piece of a printed circuit board ( two small tracks with a 2 mm distance between each other ) . This circuit is powered using a 12 volts DC power supply , so the relay used for this project must be a 12 volts relay . This circuit is working very simple , when both plates of the sensor are touched the skin resistance will activate the circuit .
Detail download here

Tuesday, August 7, 2012

Automatic DC fan Controller by Thermistor

This circuit will of turn on / off 12V DC fan Pls temperatures of above normal temperatures. You can set the turn on temperature by adjust VR1. This circuit use an NTC Thermistor, the which means Pls Surrounding the temperature decreases the resistance of this thermistor will of increase is. If the temperature increate So the voltage at pin 3 on LM311 will from decreated. The resistance of the NTC is about 10K at 25'c.

Automatic DC fan Controller by Thermistorcircuit diagram of Automatic DC fan
Controller by Thermistor

LM31 pinout
NTC thermistor that is used is a standard type. but Almost any type will do. based on the results experimented with different models from 10K to 100K and all worked fine after replacing the trimmer pot. The one-Used in the above circuit diagram was a 10K model. This 10K was measured at exactly 25 ° C and with 10% tolerance. VR1 is a regular Bourns Trimmer and adjusts a wide range of temperatures for this circuit.
Detail download here

Temperature Controlled Relays Circuit

This circuit energizes the relay when the temperature rises above the preset level. The value of the thermistor is not critical. The important thing is the voltage on pins 5 & 6. Any value thermistor should work satisfactorily. But you may need to change the value of R1 - to achieve the desired range of adjustment.
Temperature Controlled Relays Circuit

The Circuit operating temperature will adjust from about 5C to 75C (41F to 167F). However - this wide range makes the adjustment coarse. You can improve control by reducing the value of the pot and increasing the value of R2. Use R2 to take you close to the desired temperature - and use the reduced value pot to make the fine adjustment.

The relay is actually controlled by the voltage on pins 5 & 6. So - by changing the value of R2 - you can extend the range in either direction. Increasing the value of R2 - will give access to lower temperatures. And - reducing the value of R2 - will give access to higher temperatures.



This Circuit From: www.zen22142.zen.co.uk
Detail download here

Thermistor Temperature Warning Alarm

A simple 7555 buzzer circuit that will activate when a preset temperature is reached. Please note that there is no hysteresis in this circuit, so that if the temperature changes rapidly, then the buzzer alarm may activate rapidly
Thermistor Temperature Alarm CircuitThermistor Temperature Warning Alarm Circuit

7555 Pinout

The Astable multivibrator using the low power CMOS timer IC 7555 which is the low power version of the popular 555 IC. The reset pin 4 of IC1 is used to activate the alarm. The astable will work only if the reset pin 4 becomes high. The reset pin is connected to the positive rail through the 10 K NTC thermister. The thermister offers high resistance in cold and its resistance becomes low to few ohms when the temperature in its vicinity increases. So when the temperature is low reset pin of IC1 remains low and astable is in off position and buzzer remains silent. When the temperature near the thermister increases, its resistance decreases and provides voltage to the reset pin of IC1 and the astable starts working.
Detail download here

Truck Engine Idling Manual

Truck Engine Idling Manual Diesel engines play an important role in the transport of goods and services nationwide. They are a durable and economical source of power. However, there is growing concern about the health effects associated with exposure to diesel exhaust. Diesel exhaust affects everyone, but people with existing heart or lung disease, asthma, or other respiratory problems are most sensitive to the small particles in diesel exhaust. Fortunately, new emission standards and new technology are helping to ensure that the cleaner diesel engines of the future will dramatically reduce these health risks. If you drive a truck, there are several
things that you can do now to save money and reduce pollution. download Truck Engine Idling Manual
Detail download here

Monday, August 6, 2012

TGS813 Gas Alarm

This toxic gas alarm circuit is sensitive to less than 100 ppm of carbon monoxide. This alarm is useful for simple gas boats, sheds and cabins. You could save a life. Some of the companies listed in the Appendix to offer plans and kits for various toxic gas sensors.

Alarm of toxic gases it utilizes a tin-oxide-semiconductor. A coil of thin wire heated by a battery 12 V via IC1 and IC2, the which pulses the voltage to the coil of the sensor, saving a significant amount of energy. Zener diode Dl provides a constant voltage to the filament coil sensors. resistance of the sensor reduces the sensor is exposed to toxic gases Such as hydrogen, carbon monoxide and propane. Reduced to the resistance of the sensor, the SCR gate voltage increases. When the gate threshold voltage is reached, the SCR fires and a buzzer alarm is activated. Once activated, the bell and the switches S1 Should Be used to reset the alarm. Since the sensor has a good deal of thermal inertia, S1 must be off or open for about three or four minutes after the initial activation, allowing the sensor to stabilize, thus avoiding false alarms. Sensitivity control R7 set to the Desired value, before the activation of the SCR.

for more details about TGS813  Gas  Alarm  Circuit please visit http://www.free-circuit.com/toxic-gas-detector-and-alarm-circuit-with-tgs813/
Detail download here

Sunday, August 5, 2012

LS7220 Simple Electronic Combination Lock

This is the circuit  of electronic combination lock based on IC LS7220. This circuit can be used to activate a relay for controlling (on/off) any device when a preset combination of 4 digits are pressed. 
LS7220 Simple Electronic Combination Lock Circuit
IC LS7220 Pin-Out
To set the combination Lock, 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.
Detail download here

UM66 Simple Melody Doorbell

Here is a very simple and low cost to build doorbell circuit using IC UM 66. The UM66 series are CMOS IC’s designed for using in calling bell, phone and toys. It has a built in ROM programmed for playing music. The device has very low power consumption.Thanks for the CMOS technology.
UM66  Simple Melody Doorbell Circuit
UM 66 Pin-Out
If S1 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.
Detail download here

Siren Generator Circuit Using UM3561 IC

UM 3561 is a low cost siren generator designed for use in toy applications. The UM 3561 IC can generate Multi siren tones simulating Police siren, Ambulance siren, Fire brigade siren and Machine gun sound. The IC has an inbuilt oscillator and tone selection pins. It is easy to make a siren generator with only a few external components. Only one external resistor and a speaker driver transistor are sufficient to make a simple siren generator.
UM3561 vSiren Generator Circuit
UM3561 Pinout
Note:
By changing the pin connections of Sel.1 (Pin6) and Sel. 2(Pin 1) it is easy to change the siren tones.
Sel 1Sel 2Tone
Pin 6 Pin 1
NC NC Police siren
+3V NC Fire Engine sound
Gnd NC Ambulance Siren
NC +3V Machine Gun sound

Supply voltage Min. 2.4VTyp 3V Max 3.5V
Operating current Min - -180 uA

for more details about UM3561 Siren Generator Circuit please visit http://electroschematics.com/4820/um3561-siren-generator-design-2/
Detail download here

LM358N - DEW Sensor

The following schematic shows a simple DEW sensor circuit diagram using LM258N IC. As the humidity around the circuit goes up, the resistance in the DEW sensor increases. When the resistance reaches a pre-specified level, the circuitry displays a warning message, and shuts down the external device

LM358N - DEW Sensor Circuit

LM358N Pinout

Under normal conditions, resistance of the dew sensor is low (1 kilo-ohm or so) and thus the voltage at its non-inverting terminal (pin 3) is low compared to that at its inverting input (pin 2) terminal. The corresponding output of the comparator (at pin 1) is accordingly low and thus nothing happens in the circuit.

When humidity exceeds 80 per cent, the sensor resistance increases rapidly. As a result, the non-inverting pin becomes more positive than the inverting pin. This pushes up the output of IC1 to a high level. As a consequence, the LED inside the opto-coupler is energised.

At the same time LED1 provides a visual indication. The opto-coupler can be suitably interfaced to any electronic device for switching purpose. Circuit comprising diode D2, resistors R5 and R6 and capacitor C1 forms a low-voltage, low-current power supply unit. This simple arrangement obviates the requirement for a bulky and expensive step-down transformer.
Detail download here

Saturday, August 4, 2012

3 Digit Digital Frequency Counter

Digital Frequency Counter Circuit
This circuit is a digital frequency counter. It covers region 1HZ until 1MHZ. The IC1 schmitt trigger that it regulates the signal of entry and him changes in reasonable level suitable for the IC2-3-4. With the tenth pulse in the entry of IC2/1, is produced a pulse '' carry '' in the IC3/5. The same moment the IC2 causes the depiction in the display 1, The IC3 causes the display 2. When in the entry of IC3 it reaches and the tenth pulse, the display 2 and the display 3, (with total depiction 100, having the display in right order). The exit '' carry'' off IC4/5, can be used in order to it turns on the decimal point (comma) the display 1, in order to it shows a situation over the limits of measurement.

The timed begins with the one of half double timer (IC5A). Switch S1 select the interruption the time in 1sec or in 1ms. At the duration of this interruption, second half the (IC5B), it produces a interruption of depiction 2 or 3sec., at the duration which counter cut off by the entry and the displays remain OFF. In the end of depiction, a pulse RESET, begins the interruption of time/depiction.

The critical point is round the Q1-IC1, which should be placed as long as it becomes more near in the jack of entry, to reject of parasitic signals of high frequency. For the regulation, we can use a frequency counter good precision (if you do not have you are lented) and a generator of signal. We put switch S1, in place [HZ], we apply in the entry a low frequency and we regulate the trimmer TR2, so that we take the right clue, which should suit with source frequency counter We repeat also the regulation for the department of KHZ, with a higher frequency. The supply of circuit becomes with a battery +9V, if it is used as portable or from suitable power supply if it is incorporated in some unit that exists already.

List Component
R1     : 8.2Mohm          IC2-3-4 : 4026
R2-9   : 100Koh           IC5     : 556
R3     : 470Kohm          IC6     : 4007
R4     : 470 ohm          IC7     : 7805
R5-6-7 : 10Kohm           DS1-3   : Display 7segment Comm. Cath.
R8     : 3.3Mohm          TR1     : 1M ohm trimmer 
C1-2   : 1uF 63V Mylar    TR2     : 1Kohm trimmer 
C3     : 47uF 16V         Q1      : 2N930 
C4     : 100nF 63V        S1      : ON-OFF mini switch
C5     : 2.2uF 16V        S2      : 1X2 mini switch
C6     : 10uF 16V 
C7     : 10nF 63V Mylar
C8-10  : 1nF 63V Mylar 
C9     : 1uF 16V  
Detail download here

Thursday, August 2, 2012

TDA0161 Metal Detector

This metal detector circuit diagram is based on the IC TDA0161, designed for metallic body detection by detecting the variations in high frequency Eddy current losses. For detecting metals , TDA0161 require an external LC tuned circuit .
Output signal is determined by supply current changes. Independent of supply voltage, this current is high or low according to the presence or the absence of a close metallic object. This medal detector circuit use two LEDs , which offer an visual indication of presence or absence at a metals ,around the coil . To adjust the circuit you need to make sure there is no metal near the coil and then set the fine adjustment to a "Mid position". After that you need to adjust the course adjustment to turn on the LED and , adjust the fine adjustment to turn off the LED.

This metal detector electronic circuit operates over a wide range input voltage of 4 -35 volts . If you want you can use other values for the Cx capacitor and for L1 inductor ( changing this value will affect the frequency oscillation and the detection range ).
Detail download here

Wednesday, August 1, 2012

Thermistor 12VDC Fan controller Circuit

This is an automatic 12VDC fan circuit  for audio amplifiers. The circuit automatically switch ON the cooler fan whenever the temperature of the heat sink exceeds a preset level. This circuit will save a lot of energy because the cooler fan will be OFF when the amplifier is running on low volume. At low volume less heat will be dissipated and it will not trigger the cooler fan ON.
Thermistor 12VDC Fan controller Circuit

The temperature is sensed using an NTC thermistor R2. Junction of thermistor r2 and resistor R1 is connected to the inverting input (pin3) of IC1 which is wired as a comparator. The non-inverting input (pin2) is given with a reference voltage using the preset R3. As temperature increases the resistance of NTC thermistor will drop and so do the voltage across it. When the voltage at the inverting input becomes less than that of the reference voltage (set for a particular threshold temperature) the output of the comparator goes high and switches the transistor Q1 ON. This will activate the relay and the cooler fan will be switched ON. When the temperature decreases the reverse happens. LED D2 will glow when the fan is ON. Diode D1 is a freewheeling diode
Detail download here