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This circuit is a doorbell with counter , that means it counts how many times the bell is triggered . It uses a chip synthesizer sound, the HT -2811 ms nothing prevents you from using another device sound generator . The HT -2811 reproduces the sound of a " ding-dong" doorbell . Besides this ic , the circuit includes a CMOS 4026 and Display Driver IC which counts the total number of visitors .  Electronic Doorbell with Counter Circuit Diagram

Simple Battery Low Voltage Beeper circuit provides an audible and visual low voltage warning for 12V battery powered devices. When the battery voltage is above the set point (typically 11V), the circuit is idle. If the battery voltage should fall below the set point, the LED will light and the speaker will emit a periodic beeping sound to warn of the impending loss of power. The circuit was designed for monitoring solar systems, but it could also be useful for automotive and other 12V applications. Specifications: Nominal operating voltage: 12V Idle current: 6ma Low Voltage Warning current: 15ma Theory: U2 provides a 5V regulated voltage reference. U1 is wired as a comparator, it compares the fixed 5V regulated voltage to the voltage on the wiper of VR1, that is proportional to the 12V supply. When the supply drops below the set point, the output of U1 goes low, turning on Q1 and powering the beeper and the LED. The beeper consists of U4, a tone generator, and U3, a low duty cycle pu...

This is a Variable 5 to 20V DC Supply Circuit Diagram . If you are looking for a low drop voltage regulator that can provide a power supply of 1A with an output voltage of between 5V and 20V DC, National Semiconductor LM2941 Low Dropout Adjustable Regulator is that you can pick to make use of. It's a typical dropout voltage of 0.5V which means that the input supply need only must be 0.5V DC over the desired output voltage.  Variable 5 to 20V DC Supply Circuit Diagram   Its other features include internal short circuit current limit and reverse battery protection. As shown in the schematic below, the regulator has five pins which consists of the ON/OFF control, Input Voltage, Output Voltage, Ground & Adjustable pins. ON/OFF is used for the purpose of switching on & off of the regulator. The capacitors C1 & E1 are to be placed as close as feasible to the regulator.  The output of the circuit can be varied by varying the worth of potentiometer VR1 from 5V DC to 2...

This circuit automatically turns on a night lamp when bedroom light is switched off. The lamp remains ‘on’ until the light sensor senses daylight in the morning. A super-bright white LED is used as the night lamp. It gives bright and cool light in the room. When the sensor detects the daylight in the morning, a melodious morning alarm sounds. The circuit is powered from a standard 0-9V transformer. Diodes D1 through D4 rectify the AC voltage and the resulting DC voltage is smoothed by C1. Regulator IC 7806 gives regulated 6V DC to the circuit. A battery backup is provided to power the circuit when mains fails. When mains supply is available, the 9V rechargeable battery charges via diode D5 and resistor R1 with a reasonably constant current. In the event of mains failure, the battery automatically takes up the load without any delay. Diode D5 prevents the battery from discharging backwards following the mains failure and diode D6 provides current path from the battery.  Automatic Ni...

Video control and display data:  Video signal is received from TUNER, AV port(AV1,AV2,S-Video,Component) and goes to the one-chip video decoder (VCTI) which separate the R,G,B signal and passes on the signal to AD converter(AD9883) which converts 4:4:4 video format into digital and gives output to the Picture Enhancer(FLI2300).This picture enhancer improves the quality of the picture by changing the level of RGB signals. The output of this enhancer chip is fed to the deinterlacer ,which in turn goes to the Scalar (GM5221).The scalar gives the output on the LVDS cable which is connected to LCD module.  VCTi acts a micom and is responsible for video processing and audio signal processing. It accepts the RF signal and separates sound and picture from it.  Scaler is responsible for regulating the timing of signal to LCD panel and size and location of the signal. Graphic control accepts the PC(Analog RGB) and DVI-D (Digital ) signal, Scalar is responsible for regulating the ti...

This is a Small Circuit Multiband Radio -Transmitter CW for who wants to learn more about radiofrequency, mainly operating principle from radios transceivers multiband, That circuit consists of a frequency oscillator RF, which is the main component us transmitters and radio receivers.  He oscillates for high frequency, he is called variable frequency oscillator or VFO, their frequency may vary of 5.2 MHz to 15 MHz, depending the coil chosen and signal can be received in the band shortwave by any receiver radio.In S1 is used a switch type bell, but can-if use a handler CW, these used by radio amateurs. How antenna should-if use a the type dipole from 1/4 wave.

Build a Park Assist Circuit Diagram . This is a Simple Park Assist Circuit Diagram. This Park Assist circuit was designed as an aid in parking the car near the garage wall when backing up. LED D7 illuminates when bumper-wall distance is about 20 cm., D7+D6 illuminate at about 10 cm. and D7+D6+D5 at about 6 cm. In this manner you are alerted when approaching too close to the wall. All distances mentioned before can vary, depending on infra-red transmitting and receiving LEDs used and are mostly affected by the color of the reflecting surface. Black surfaces lower greatly the device sensitivity. Obviously, you can use this circuit in other applications like liquids level detection, proximity devices etc.  Simple Park Assist Circuit Diagram

DC-DC CONVERTER This block provides adjustable output voltages of 9.2V, -6V, 18V and 3 to 4V for the panel. It consists of a Q114 transistor and power switch IC I108 (AIC 1526-1). When DC_ EN signal is high, then Q114 is activated and send one signal to activate I108. At this time I108 will send 200KHz 12V PWM to Q106, Which is connected with L111, Q106, D203 and C308, to boost 5V to 9.2V. And I108 offers the adjustable voltage of 3V to 4V. By sending out pulses from pin 2 and pin 16 of I108 to double voltage circuit consisting of C301, D201, D202 and C303, leaner regulator with Q105, would output –6V, 18V output id created, according to the rule of –6V creation. Inverter In order to drive the CCFLs embedded in the panel module; there is a ROYER inverter to convert to convert the input 12V up to hundreds of AC voltage output.  The inverter is formed by symmetric, in order to drive the separate lamp modules. The input stage consists of a PWM controller, buck choke, and switching MOS...

Video amplifier circuit is simple and can be used. Video amplifier circuit was constructed from 2 pieces of transistors BC550 and BC560. The source voltage used for supplying the video amplifier circuit is 5VDC. Video amplifier circuit is equipped with a powerful regulator which flows through both transistors T1 and T2, the components used to manage these flows are P1 and P2. Video Amplifier Circuit Diagrams Then the video amplifier circuit is also equipped with limiting the maximum current that passes through T1 and T2. The components in black block functions as limiting the maximum current that is passed by the T1 and T2 for no more than 5mA.

Application Circuit:  2.1W Audio Power Amplifier Circuit Datasheet for AN7148: Download

TDA Amplifier Circuit stereo 150W The TDA8950 is a high-efficiency Class D audio power amplifier. The typical output power is 2 × 150 W with a speaker load impedance of 4 Ω. The TDA8950 is available in both HSOP24 and DBS23P power packages. The amplifier operates over a wide supply voltage range from ±12.5 V to ±40 V and features low quiescent current consumption. The TDA8950 is a two-channel audio power amplifier that uses Class D technology. For each channel, the audio input signal is converted into a digital PWM signal using an analog input stage and a PWM modulator. To drive the output power transistors, the digital PWM signal is fed to a control and handshake block and to highand low-side driver circuits. This level-shifts the low-power digital PWM signal from a logic level to a high-power PWM signal switching between the main supply lines. A 2nd-order low-pass filter converts the PWM signal to an analog audio signal that can be used to drive a loudspeaker. TDA Amplifier Circuit...

Schematic: Microlab A6612 and Microlab A6331 Home Theater system .  Used ICs:  4558 – TDA7377 – TC4053 – TDA2030A A6331 - Circuit Diagram A6612 Circuit Diagram Click on the schematics to magnify

This is a project of Simple Mains Voltage Monitor Circuit Diagram. Many electronics hobbyists will have experienced the following: you try to finish a project late at night, and the mains supply fails. Whether that is caused by the electricity board or your carelessness isn’t really important. In any case, at such times you may find yourself without a torch or with flat batteries. There is no need to panic, as this circuit provides an emergency light. When the mains fails, the mains voltage monitor turns on five super bright LEDs, which are fed from a 9 V battery (NiCd or NiMH) or 7 AA cells. A buzzer has also been included, which should wake you from your sleep when the mains fails. You obviously wouldn’t want to oversleep because your clock radio had reset, would you? When the mains voltage is present, the battery is charged via relay Re1, diode D8 and resistor R10. D8 prevents the battery voltage from powering the relay, and makes sure that the relay switches off when the mains vol...

This simple circuit can be used to program the PIC16F84 and similar "flash memory" type parts. It uses a cheap 555 timer IC to generate the programming voltage from a +5V rail, allowing the circuit to be powered from a computer’s USB port. The 555 timer (IC1) is configured as a free-running oscillator, with a frequency of about 6.5kHz. The output of the timer drives four 100nF capacitors and 1N4148 diodes wir-ed in a Cockroft-Walton voltage multiplier configuration. USB-Powered PIC Programmer Circuit diagram: USB-Powered PIC Programmer Circuit Diagram The output of the multiplier is switched through to the MCLR/Vpp pin of the PIC during programming via a 4N28 optocoupler. Diodes ZD1 and D5 between the MCLR/Vpp pin and ground clamp the output of the multiplier to about 13.6V, ensuring that the maximum input voltage (Vihh) of the PIC is not exceeded. A 100kΩ resistor pulls the pin down to a valid logic low level (Vil) when the optocoupler is not conducting. The circuit is compa...

This circuit use TA7222AP to amplifiers audio signal .The price only $0.99 and can provide 5.8 watt with Muting Control.Power supply can use for 8-12Vdc it is a good idea to use for car audio power amp , coin-op machine game, security system etc. link Fig 1. TA7222AP pin out Pin Name Description 1 Vcc Supply Voltage 2 RR Ripple Reject 3 MC Muting control 4 OP AF Signal Input 5 FB FB Filter 6 GA Gain adjust 7 GND Ground 8 GND Ground 9 OP AF Output 10 BS BootStrap Fig 2. schematic for 5.8 watt audio power amplifier

 At this point is a Solar Charger Circuit to is used to charge information Acid otherwise Ni-album batteries using the solar energy power. The circuit harvests solar energy to charge a 6 volt 4.5 Ah rechargeable battery in favor of various applications. The stallion has Voltage and Current supervision and terminated voltage restrict sour facilities. Circuit uses a 12 volt solar panel and a changeable voltage supervisor IC LM 317 . The solar panel consists of solar cells each one rated on 1.2 volts. 12 volt DC is presented from the panel to charge the battery. Charging current passes through D1 to the voltage watchdog IC LM 317. By adjusting its Adjust pin, output voltage and current can subsist regulated. VR is placed amid the adjust pin and ground to provide an output voltage of 9 volts to the battery. Resistor R3 confine the charging current and diode D2 prevents discharge of current from the battery. Transistor T1 and Zener diode ZD conduct yourself having the status of a stop ...

Battery-life measurement for a portable system is a time-consuming task and many methods used for it do not give reliable results. Presented here is a circuit using which you can measure the battery-life very easily. Here, an analogue clock tracks the discharge time of the battery used in battery-powered portable devices. Circuit and working The circuit for battery-discharge measurement is shown in Fig. 1. It is built using low-power single-/dual-supply comparator MAX921 (IC1), MOSFET VN0300L (IRF1), an analogue clock and a few other components. IC1 monitors the life of the BUT (battery under test) and controls the power supply for the analogue clock. When the BUT voltage falls below the threshold value set by VR1, IC1’s output becomes low, which turns off MOSFET IRF1. This means, power supply for the analogue clock is cut off and so the clock stops running. The reading on the clock at this point gives the discharge time of the BUT, provided you had set the clock to 12:00 before testin...

This 16 LED Chaser Circuit Diagram is a double direction flash. Similar to Digital Ping- Pong 1, there is a movement of a lit dot, up and down along the LED's length. 16 LED Chaser Circuit Diagram When the D16 lit the situation changes and there is a reverse movement. Lit D15-14 ……D16, is lit making circles when the circuit is under power. The IC1 is an unstable flip- flop supplying with stable frequency pulses (the frequency can be changed by TR1, adjusting the velocity of the LED's up and down). This frequency supplies the IC3 (which is a 4-Bit UP and DOWN counter) through 2 gates A-B of the IC2. The output counter supplies the IC4 that is the driver of the LED's. The parts C- D of The IC2, make a R-S flip- flop, that changes situation, when the edge LED's D1 and D16 lit. We have an electronic limit for the situation change. In proportion the shape we make with the LED's, we can have the proportionate optional result, making various effects. Part List R1= 100Kohm...

For several years now, a rear fog lamp has been mandatory for trailers and caravans in order to improve visibility under foggy conditions. Circuit diagram : Fog Lamp Sensor Circuit Diagram When this fog lamp is switched on, the fog lamp of the pulling vehicle must be switched off to avoid irritating reflections. For this purpose, a mechanical switch is now built into the 13-way female connector in order to switch off the fog lamp of the pulling vehicle and switch on the fog lamp of the trailer or caravan. For anyone who uses a 7-way connector, this switching can also be implemented electronically with the aid of the circuit illustrated here. Here a type P521 optocoupler detects whether the fog lamp of the caravan or trailer is connected. If the fog lamp is switched on in the car, a current flows through the caravan fog lamp via diodes D1 and D2. This causes the LED in the optocoupler to light up, with the result that the phototransistor conducts and energises the relay via transistor ...

This is a Line Frequency Square Wave Generator Circuit Project. A square wave is a non-sinusoidal periodic waveform (which can be represented as an infinite summation of sinusoidal waves), in which the amplitude alternates at a steady frequency between fixed minimum and maximum values, with the same duration at minimum and maximum.   Line Frequency Square Wave Generator Circuit The transition between minimum to maximum is instantaneous for an ideal square wave; this is not realisable in physical systems. Line Frequency Square Wave Generator Circuit Project with only three components and a buffer, a line frequency square wave having a 1:1 duty cycle may be derived from the power supply.  During the alternate half-cycle, however, A is effectively clamped to - 0.7 V by Dl in the bridge which offsets the forward voltage across D2 giving an input to IC1 of approximately 0 V. When A rises above + 5 V, D2 is reverse biased and remains at +5 V. Rl is needed to load the transfor...