Automatic changeover circuit

Description.
 The circuit diagram shown here is of a automatic changeover switch using IC LTC4412 from Linear Technologies. This circuit can be used for the automatic switchover of a load between a battery and a wall adapter.LTC4412 controls an external P-channel MOSFET to create a near ideal diode function for power switch over and load sharing. This makes the LT4412 an ideal replacement for power supply ORing diodes. A wide range of MOSFETs can be driven using the IC and this gives much flexibility in terms of load current. The LT4412 also has a bunch of good features like reverse battery protection, manual control input, MOSFET gate protection clamp etc. The diode D1 prevents the reverse flow of current to the wall adapter when there is no mains supply. Capacitor C1 is the output filter capacitor. Pin 4 of the IC is called the status output. When wall adapter input is present the status output pin will be high and this can be used to enable another auxiliary P-channel MOSFET (not shown in the circuit diagram).

Circuit diagram.

12 Volt to 230 Volt Inverter Circuit Diagram Using IC 555 Description

Description
Circuit showing a 12 volt to 230 volt inverter. Here we have used a astable multivariate for
making square wave pulse. The frequency of the square wave signal is high
and the voltage is 9v.There for the primary output voltage is almost equal to 230 volt. Here need a 12
volt power supply. Click here for the power supply circuit

Components Required

Resistor 10 k, 47k,1k 2W
Capacitor 103 pf -2
Transistor SL 100
IC NE 555
Transformer 9-0,230 VOLT PRIMARY

40 Channels of Programmable Voltage with Excellent Temperature Drift Performance Using the AD5380 DAC

CIRCUIT FUNCTION AND BENEFITS
 This circuit is a multichannel DAC configuration with excellent temperature drift performance. It provides 40 individual output voltage channels with 14 bits of resolution and a temperature stability of typically less than 3 ppm/°C.

CIRCUIT DESCRIPTION
Figure 1 shows a typical configuration for the AD5380-5 when configured for use with an external reference. In the circuit shown, all AGND, SIGNAL_GND, and DAC_GND pins are tied together to a common AGND. AGND and DGND are connected together at the AD5380 device. On power-up, the AD5380 defaults to external reference operation. This design uses two separate 5.0 V power supplies—one to power the voltage reference and the analog portion of the AD5380 (AVDD) and the other to power the digital portion of the AD5380 (DVDD). For best performance, a linear regulator should always be used to power the analog portion of the circuit. If a switching regulator is used to power the digital portion, care should be taken to minimize switching noise at the DVDD supply pins. Additional decoupling using a series connected ferrite bead may be required. The AD5380 digital (DVDD) power supply can operate from a 3 V or 5 V supply, which provides for maximum flexibility when interfacing to digital components. Both supplies can be tied together to a common 5 V supply; it is derived from a linear regulator. Refer to the ADIsimPower™ design tool for guidance on the power supply designs.

BENCH POWER SUPPLY

Description
Here is a regulated power supply for you bench. The 100n capacitors are needed across the input and output of the regulator IC's to prevent high-frequency instability.

Circuit Diagram

AC DETECTOR

Description This circuit will detect AC line currents of about 250mA or more without making any electrical connections to the line. Current is detected by passing on of the AC lines through an inductive pickup (L1) made with a 1 inch diameter U-bolt wound with 800 turns of #35 magnet wire. The pickup can be made from other iron type rings or transformer cores that allows enough space to pass one of the AC lines through the center. Only one of the current carrying lines, either the line or the neutral should be put through the center of the pickup to avoid the fields cancelling. This is most important is very difficult to achieve. The best method is to make a short extension cord with the three conductors separated from each other. If you make a 3-turn loop with say the active line, and pass a straight rod such as a metal bolt, containing 400 or more turns through the centre of the 3-turns, you will produce a very sensitive pick-up. The magnetic pickup produces about 4 millivolts for AC line current of 250mA, or AC load of around 30 watts. The signal from the pickup is increased about 200 times at the output of the op-amp pin 7 which is then peak detected by the capacitor and diode connected to pin 7. The second op-amp is used as a comparator which detects a voltage rise greater than the diode drop. The minimum signal needed to cause the comparator stage output to switch positive is around 800mV which corresponds to about a 30 watt load on the AC line. The output of the 1458 op-amp will only swing within a couple volts of ground so a voltage divider (1k/470) is used to reduce the no signal voltage to about 0.7 volts. An additional diode is added in series with the transistor base to ensure it turns off when the op-amp voltage is 2 volts. You may get a little bit of relay chatter if the AC load is close to the switching point so a larger load of 50 watts or more is recommended. The sensitivity can be increased by adding more turns to the pickup.

Circuit Diagram

CONSTANT CURRENT SOURCE

Description In the following circuit an LED is used to give a fixed reference voltage to a transistor. The output constant current I out is given by: The LED lights up only when a load is connected at the output. Thus it indicates when the circuit is operating. The operation of the circuit can be made clearer by re-arranging the components as follows: The output will be limited to 100mA by using a red LED and 10R for Re. The output will be limited to 500mA by using a red LED and 2R2 for Re. The output will be limited to 1A by using a red LED and 1R0 for Re. Circuit Diagram

AUTO GENERATOR REGULATOR

This regulator controls a dc generator. D4 prevents the battery from discharging through the generator and takes the place of the mechanical cut-out relay. R10 adjusts the system voltage setting. Circuit Diagram

DISCRETE CURRENT BOOSTER

DIFFERENTIAL VOLTAGE OR CURRENT ALARM

The input may be dc or low frequency ac. The output is a distinctive series of audio beeps or a continuous tone, and occurs only when a selected polarity unbalance is present at the input. Circuit Diagram