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This circuit is a simple form of the commercial UPS , the circuit provides a constant regulated 5 Volt output and an unregulated 12 Volt supply. In the event of electrical supply line failure the battery takes over, with no spikes on the regulated supply. This circuit can be adapted for other regulated and unregulated voltages by using different regulators and batteries. For a 15 Volt regulated supply use two 12 Volt batteries in series and a 7815 regulator . There is a lot of flexibility in this circuit. TR1 has a primary matched to the local electrical supply which is 240 Volts in the UK. The secondary winding should be rated at least 12 Volts at 2 amp, but can be higher, for example 15 Volts. FS1 is a slow blow type and protects against short circuits on the output, or indeed a faulty cell in a rechargeable battery. LED 1 will light ONLY when the electricity supply is present, with a power failure the LED will go out and output voltage is maintained by the battery. The circuit bel...

This is a 22-W Amplifier circuit that is designed for or 12-V DC power supply Systems. There are many application for  this circuit,  such as in car audio  application. In car electrical  power supply system, the 12V power supply will be provided by the host vehicle’s battery.  The capacitor C3 is used to give ripple rejection, since noisy power supply voltage is common in automotive electrical system. The power supply noise signal on car power supply is decoupled by the capacitors C2 and C1.  Smaller capacitor C2 is needed to decouple the high frequency noise, since the larger cap (C1) usually has high equivalent series inductance that prevent the high frequency noise  (such as glitch or spike) to be bypassed.  The capacitors C5 couple the incoming audio signal to IC1 while decoupling static DC offset. For better bass response, this circuit prevent rolling off of the low audio frequencies by choosing a relatively large capacitance for small sign...

If you want to check the behaviour of an electronic circuit at low voltages, an adjustable power supply as shown here may be helpful. Powered from a 3 to 16 volts source (DC for sure), it will provide a stable output voltage in the 0 to 1.5 V range. Adjustable Low-voltage Power Supply Circuit Diagram Multiturn trimpot P1 allows the output volt-age to be adjusted with good precision. The BC337-400 output transistor raises the out-put current to about 200 mA bearing in mind that the minimum supply voltage is 3.5 V. The transistor’s dissipation should be taken into account, and a more power ful t ype used if necessary. T1 may be omitted and R2 replaced with a wire link if you are happy with 3 mA at 3 volts out, 10 mA at 6 V or 20-30 mA at 10-16 V. These values represent the maximum output current of the TLC271 op amp. Without T1, the minimum supply voltage is 3.0 V. Author:Vladimir Mitrovic - Copyright: Elektor

This a simple 15v variable power supply circuit is using 2N3055 transistors. Output voltage of this variable power supply can be adjusted in the range between 1.5 and 15 volts. 15V Variable Power Supply Circuit Diagram: This 2N3055 15v variable power supply can provide a maximum current of 500 mA. Stabilization is better than 2%, if the currents do not exceed 350 mA. Voltage is set using a potentiometer, and the presence of overload is announced by an audible indication of overload. T4 transistor compare the voltage at the cursor P1 with the output. When this voltage is higher with 0.65 V than regulated voltage, T2 opens, leading to suppression of the current Darlington power stage, T3-T5. In this mode, the output voltage of the source is higher than 0.65 V reference voltage on the base of T4, which comes from a 15 V zener diode.

Regulated DC Power Supply using transistors. A low ripple regulated DC power supply designed based on transistors is shown here. Such transistor voltage regulators are suitable for application where high output current is required. Conventional integrated series regulators like 7805 can only deliver up to 1A. Additional series pass transistors have to be added to the 7805 based regulator circuit for improving their current capacity. Description. The circuit shown below is a basic series voltage regulator based on transistors. Transistor Q1 (2N 3054) and Q2 (2N 3055) form a darlington pair. Resistor R1 provides the base current for Q1 and also keeps the zener diode D2 in the active region. The overall working of the circuit can be demonstrated by explaining two situations. When the input voltage (output of the rectifier section) increases, the output voltage of the regulator (Vout) also increases. This increase in Vout decreases the base emitter voltage of Q2 because the zener diode D2...

Project Description This is a very easy to build power supply that is based on LM338 5A adjustable voltage regulator. I am using the supply for a long time, have no problem yet. Only current adjust is missing but I overcome this situation by using an LCD panel ampermeter.  There is no PCB for the circuit. I took a 3x16 copper plate and strip the unused areas by a knife. If you want you can use analog meters instead of LCD panels.    Notes Use thick wires for connections.When connecting the LM338 to the heatsink use thermal paste. Use external supplies for LCD panels. They can be 9V batteries. The panels I use draws 1mA current and the batteries last sufficiently long time. If you have small transformers which can supply regulated 9V, you can use them. You need separate transformers for each panel!The transformer should be 100 Watt but if you don't need high current you can try transformers that you already have. (I can draw 6A from 100Watt transformer.)If you have ...

Here is a simple Electronic Project for battery replacement power supply to build easy.  Your child's battery toy has failed and you have to fix it. Once you have managed to get it apart, the battery compartment is not likely to be connected to the works or the batteries might have gone flat anyway. The solution is this switchable supply which is designed to replace from one to six dry cells. It is not intended to replace the batteries on a permanent basis, as in most cases this is not practical. Battery Replacement Power Supply Circuit Diagram: The heart of the supply is an LM317T adjustable 3-terminal regulator and six trimpots selected by switch S1b. The other pole of the switch, S1a, is used to select taps on the transformer secondary, to minimize power dissipation in the LM317T. The table shows the trimpot settings for the six voltage outputs. Diode D1 and the 10µF capacitor and the LED provide power indication. This has the advantage of constant brightness which would not be...

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

To make 12Volt 35 Amp Power Supply such as those titles can using LM7812 voltage regulator as the regulator 12 Volt DC and as a power supply can use transistor  TIP2955 . Series Power Supply 12Volt 35 Amp uses 6 units TIP2955 type power regulator transistors. I use a type MJ2955 TIP2955 not because packaging TIP2955 easier to install heatsink. The series 12Volt 35 Amp Power Supply can be loaded up to 35A depending on the travo which we attach. The series 12Volt 35 Amp Power Supply is very simple, because the voltage regulators make use of IC7812 which will leave a power regulator alone. For more details, series 12Volt 35 Amp Power Supply can be seen in thethe following figure . 12Volt 35Ampere schematic If want the maximum currents up to 35A not only reduced the live circuit TIP2955nya power regulator, no need to 6 levels as seen in the image series 35 Ampere Power Supply 12Volt above.

Supply Voltage Indicator Circuit Diagram. A novel supply voltage monitor which uses a LED to show the status of a power supply.This simple and slightly odd circuit can clearly show the level of the supply voltage (in a larger device): as long as the indicator has good 12 volts at its input, LED1 gives steady, uninterrupted (for the naked eye) yellow light. If the input voltage falls below 11 V, LED1 will start to blink and the blinking will just get slower and slower if the voltage drops further - giving very clear and intuitive representation of the supply's status. The blinking will stop and LED1 will finally go out at a little below 9 volts. On the other hand, if the input voltage rises to 13 V, LED2 will start to glow, getting at almost full power at 14 V. The characteristic voltages can be adjusted primarily by adjusting the values of R1 and R4. The base-emitter diode of T2 basically just stands in for a zener diode. Supply Voltage Indicator Circuit Diagram Supply Voltage Ind...

Description : This schematics is of dual power supply, having voltage output 3,5,6,9,12,15 and -3,-5,-6,-9,-12,-15. LM 317 is adjustable 3-terminal positive voltage regulator and LM 337 is adjustable 3-terminal negative voltage regulator. Switch S1 is for +ve and S2 is for -ve voltage respectively. Schematic: click on image to zoom Pin out: Components: All diode s are 1N4007 R1, R3 270 ohm R2 1K2 ohm R4, R10 390 ohm R5, R11 820 ohm R6, R12 1K ohm R7, R13 1K65 ohm R8, R14 2K35 ohm R9, R15 3K ohm LM317T LM337T C5, C8 2200uF 25v electrolyte C6, C7, C9, C10 22uF 25v electrolyte C1-C4 0.1uF Ceramic F1 0.5A fuse S Switch S1, S2 6-way rotary switch T1 Center taped transformer 15-0-15v 220v Red LED

This circuit is a very simple voltage monitoring device for +5V VCC supply lines. It can be used to monitor the power supply of a microcontroller (uC) by indicating when the supply level raises above a pre-defined value. The output of the circuit can interface directly to digital logic, reset the microcontroller or turn off the connected microcontroller circuitry before it goes toasted owing to an improper power supply voltage. The ‘proof of concept’ is verified using the eternal single supply dual operational amplifier LM393. However, feel free to try other possible alternatives like LM2903, LM193, etc. The LM393 consist of two independent voltage comparators that are designed to operate from a single supply over a wide range of voltages (2V-36V). The outputs can be connected to other open-collector outputs to achieve wired-AND relationships. The comparator compares two voltages, IN1 at the inverting (–) input and IN2 at the inverting (+) input. When IN2 < IN1, the comparator outpu...

This circuit will supply up to about 20ma at 12 volts. It uses capacitive reactance instead of resistance; and it doesn't generate very much heat.The circuit draws about 30ma AC. Always use a fuse and/or a fusible resistor to be on the safe side. The values given are only a guide. There should be more than enough power available for timers, light operated switches, temperature controllers etc, provided that you use an optical isolator as your circuit's output device. (E.g. MOC 3010/3020) If a relay is unavoidable, use one with a mains voltage coil and switch the coil using the optical isolator.C1 should be of the 'suppressor type'; made to be connected directly across the incoming Mains Supply. They are generally covered with the logos of several different Safety Standards Authorities. If you need more current, use a larger value capacitor; or put two in parallel; but be careful of what you are doing to the Watts. The low voltage 'AC' is supplied by ZD1 and Z...

Simple and cheap, the circuit built based on well-known IC regulator LM317 with current booster of power transistor 2N3782. Don’t forget to add heatsink especially for power transistor 2N3782.

A regulated power supply converts unregulated AC into a constant DC with the help of a voltage rectifier. Its function is to supply a stable voltage (or less often current), to a circuit or device that must be operated within certain power supply limits. Any deviation from these rating can damage the devices. Some DC power supplies use AC mains electricity as an energy source. Such power supplies will employ a transformer to convert the input voltage to a lower AC voltage. A rectifier is used to convert the transformer output voltage to a varying DC voltage, which in turn is passed through an electronic filter to convert it to an unregulated DC voltage. The filter removes most, but not all of the AC voltage variations; the remaining voltage variations are known as ripple . Types: Fixed Voltage Power Supply Variable Voltage Power Supply Fixed Voltage Power Supply The unregulated DC output is fixed to a constant voltage level by using a voltage regulator. Commonly used fixed voltage valu...

This Electronic circuit Project a very interesting  split power supply circuit can be constructed using this schematic diagram which is based on a LM380 audio power IC . The regulation of the output voltage depends of the upon circuit feeding the LM380 . The power dissipation is around 1 watt so an small heatsink may be required . If the power dissipation is exceeded , the device will go into thermal shut-down protection . Split Power Supply Circuit Diagram: Current limiting occurs if the output current exceeds 1.3 A  . The R1 linear potentiometer is , should be initially set to mid level  , is used nullify any imbalance in the output . This split power supply circuit should not be used for input voltages which exceed 20 volts . Use this circuit after a regulated power supply circuit , but try to keep the specifications for the maximum rating of this split voltage circuit .

This is a simple Bench Power Supply Circuit Diagram . This is a 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.   Simple Bench Power Supply Circuit Diagram

This 30v variable power supply circuit is based on LM317  voltage regulator circuit . This LM317 30v variable power supply circuit can deliver high current (around 5 amps) and variable output voltage between 1.2 volts, up to 30 volts. The led D3 mounted on pin 6 at lm301 lights in constant current mode . 30V Variable Power Supply Using LM317 Circuit diagram  Current limit can be adjusted using R2 potentiometer and the output voltage can be adjusted from 1.2 volts to 30 volts using R8 potentiometer . Input voltage for this variable power supply must be around 35 volts .For this power supply circuit you need to use LM317K circuit (in to3 package ) which must be mounted on a heatsink .

This is a project of 1.2-30V/1.5A Variable Regulated Power supply, This is simple 1.2-30V/1.5A variable regulated power supply circuit diagram The 110V-AC coming from the powercord is fed to the transformer TR1 via the on-off switch and the 500mA fuse. The 30vac output (approximately) from the transformer is presented to the BR1, the bridge-rectifier, and here rectified from AC (Alternating Current) to DC (Direct Current). If you don't want to spend the money for a Bridge Rectifier, you can easily use four general purpose 1N4004 diodes. The pulsating DC output is filtered via the 2200µF capacitor (to make it more manageable for the regulator) and fed to 'IN'-put of the adjustable LM317 regulator (IC1). The output of this regulator is your adjustable voltage of 1.2 to 30volts varied via the 'Adj' pin and the 5K potmeter P1. The large value of C1 makes for a good, low ripple output voltage.  1.2-30V/1.5A Variable Regulated Power supply Circuit Diagram Why exactly 1.2V...

The schematic above can be used for supply on color TV for all type TV circuit. But we need to know how much voltage needed by the circuit of color Television. To set the output voltage, the setting on VR1 1K ohm. Required input voltage 300V DC which is already on TV circuit, so we just take a 300V dc voltage existing on the TV circuit, and for a circuit supply voltage on our TV cut the line PCB and connected with this  universal switching power supply.For the transformer we can use the TV regulator transformer. Part List : R1 = 33R 5W R2 = 330R 1W R3 = 2K2 R4 = 47K R5 = 2K7 R6 = 22K R7 = 390K R8 = 47R 1W C1 = 100uF 25V C2 = 1n2 2KV C3 = 18n C4 = 18n D1 = 1N4148 D2 = 1N4148 D3 = ZD 12V D4 = 1N4007 D5 = 1N4007 VR1 = 1K ZD1 = Zener 6V T1    = TV regulator transformer Q1   = K2847 Q2   = C2328A PCB line Finishes circuit