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A very simple variable power supply circuit can be made using this electronic circuit diagram .This variable regulator circuit will provide an variable regulated output voltage , between 0 and 50 volts . The CA3140 operational amplifier compares the regulator output to a reference voltage , that depends on the R9 value. Simple 0V to 50 Volt Variable Regulator Circuit Diagram  The output voltage will be nominally twice the voltage between the positive input ( noninverting ) of the CA3140 and ground . The unregulated input voltage must be around 60 volts The output voltage can be set between 0 an 50 volts using R9 potentiometer .The 2N3055 transistors must be mounted on a heatsink , to prevent the overheating of transistors .

This inverter circuit can provide up to 800mA of 12V power from a 6V supply. For example, you could run 12V car accessories in a 6V (British?) car. The circuit is simple, about 75% efficient and quite useful. By changing just a few components, you can also modify it for different voltages. Part List: R1, R4 2.2K 1/4W Resistor R2, R3 4.7K 1/4W Resistor R5 1K 1/4W Resistor R6 1.5K 1/4W Resistor R7 33K 1/4W Resistor R8 10K 1/4W Resistor C1,C2 0.1uF Ceramic Disc Capacitor C3 470uF 25V Electrolytic Capcitor D1 1N914 Diode D2 1N4004 Diode D3 12V 400mW Zener Diode Q1, Q2, Q4 BC547 NPN Transistor Q3 BD679 NPN Transistor L1 See Notes MISC Heatsink For Q3, Binding Posts (For Input/Output), Wire, Board source:LINK

This is a Simple LED Volt meter to Monitor the charge level in Lead Acid Battery or Tubular battery. The terminal voltage of the battery is indicated through a four level LED indicators. The nominal terminal voltage of a Lead Acid battery is 13.8 volts and that of a Tubular battery is 14.8 volts when fully charged.  Simple LED Volt Meter Circuit Diagram The LED voltmeter uses four Zener diodes to light the LEDs at the precise breakdown voltage of the Zener diodes. Usually the Zener diode requires 1.6 volts in excess than its prescribed value to reach the breakdown threshold level. When the battery holds 13.6 volts or more, all the Zener breakdown and all LEDs light up. When the battery is discharged below 10.6 volts, all the LEDs remain dark. So depending on the terminal voltage of the battery, LEDs light up one by one or turns off.

This circuit is a DC voltage output from a small DC input generate large voltage.It ‘s easy and quick to do, and reducing the value of the Z-diode, the circuit can be universally adapted to other output devices of the circuit voltages. The give and all diagrams represent a DC converter with 12V battery 9 volt DC input and output.     12-9 Volt DC to DC Converter Circuit Diagram With the 10V zener diode, as in the diagram, the output voltage is approximately 9.3 volts DC. The supply voltage is used, should always be at least a few volts higher than the Zener voltage. In this example, I have a 12 Volt DC battery to provide regulated 9-volt DC output.

This circuit lets you control a pump, to keep the level of water in a cellar below a certain threshold, for example. Power  is supplied to the pump by a battery that is recharged auto matically when the AC power line voltage is present. Circuit Diagram 12-volt Cellar Drain Pump Circuit Diagram lf the water  level  rises, the electrodes touch the liquid and a current begins to flow. The transistor then conducts and the pump runs. The pump stops when the water level has dropped sufficiently for the electrodes to no longer be in contact with it but not straight away, as the voltage on the transistor gate is maintained for a few seconds more by the 470 ytF capacitor. This makes it possible to ensure  the electrodes are completely clear of the water. The battery is constantly tested by the comparator circuit around the T1071 lC.  lts output drives the  gate of the triac  in the transformer primary circuit via the optoisolator. The transformer secondary charges the battery via the rect...

Here I will explain about the necessary voltage and power amplifier output. The voltage should have at least approximately 9Volt 30Volt voltage and maximum voltage on the DC current. For maximum output of 2 X 2Watt with impedance 8-16 ohm. Because this amplifier circuit using ic and ic is used have the equation, so that if used different ic, then the required output voltage and also differ depending ic respectively. Part List : Resistor R1 = 1M R2 = 1M R3 = 1K R4 = 1K R5 = 100K R6 = 100K R7 = 1R R8 = 1R Capacitor C1 = 1uF C2 = 220uF C3 = 1uF C4 = 100uF C5 = 5uF C6 = 5uF C7 = 0.1uF C8 = 220uF C9 = 220uF C10 = 0.1uF IC U1 = ULN2274B , ULN2277 , ULN2278B

This circuit above uses a 13 volt zener diode, D2 which provides the voltage regulation. Aprroximately 0.7 Volts are dropped across the transistors b-e junction, leaving a higher current 12.3 Volt output supply. This circuit can supply loads of up to 500 mA. This circuit is also known as an amplified zener circuit.

For this time I will post the scheme following an amplifier of the IC KA2203, SN16975, TBA820, UL1482P. Which has 4 Watt power output with 4 Ohm impedance. At least 8 Volt supply voltage and a maximum of 20 volts. Part List R1 = 100K R2 = 56R  R3 = 56R Use 1/2 W resistor C1 = 47uF C2 = 100uF C3 = 100uF C4 = 470uF C5 = 470pF C6 = 0.22uF C7 = 100uF U1 = KA2203 , SN16975, TBA820, UL1482P

Kit that can change the normal 12v dc voltage from a car battery, battery bike 12V motor. With the current 7A. so this circuit is very suitable for power car amplifiers and sound systems that use simple 12V battery. Kit converter is also equipped with inputs "SEND" to activate the circuit and also send this interchangeable inputs is connected to the Tape / cd / dvd player of your car. And input "send" is if the non-connected with an output of "send" player car you then connect it to +12 hrs on v from the battery / batteries The series is already in the test kit and has been functioning normally.

Description  In the circuit below, a quad voltage comparator (LM339) is used as a simple bar graph meter to indicate the charge condition of a 12 volt, lead acid battery. A 5 volt reference voltage is connected to each of the (+) inputs of the four comparators and the (-) inputs are connected to successive points along a voltage divider. The LEDs will illuminate when the voltage at the negative (-) input exceeds the reference voltage. Calibration can be done by adjusting the 2K potentiometer so that all four LEDs illuminate when the battery voltage is 12.7 volts, indicating full charge with no load on the battery. At 11.7 volts, the LEDs should be off indicating a dead battery. Each LED represents an approximate 25% change in charge condition or 300 millivolts, so that 3 LEDs indicate 75%, 2 LEDs indicate 50%, etc. The actual voltages will depend on temperature conditions and battery type, wet cell, gel cell etc. Circuit Diagram  Source - http://www.bowdenshobbycircuits.info/...