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Construction Standard Variable Resistor Photograph © Rapid Electronics Variable resistors consist of a resistance   track   with connections at both ends and a   wiper   which moves along the track as you turn the spindle. The track may be made from carbon, cermet (ceramic and metal mixture) or a coil of wire (for low resistances). The track is usually rotary but straight track versions, usually called sliders, are also available. Variable resistors may be used as a rheostat with  two  connections (the wiper and just one end of the track) or as a potentiometer with all  three  connections in use. Miniature versions called presets are made for setting up circuits which will not require further adjustment. Variable resistors are often called  potentiometers  in books and catalogues. They are specified by their maximum resistance, linear or logarithmic track, and their physical size. The standard spindle d...

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 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.

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...

Description: A truly timeless circuit. LM317 is a versatile and highly efficient 1.2-37V voltage regulator that can provide up to 1.5A of current with a large heat sink. It's ideal for just about any application. This was my first workbench power supply and I still use it. Since LM317 is protected against short-circuit, no fuse is necessary. Thanks to automatic thermal shutdown, it will turn off if heating excessively. All in all, a very powerful (and affordable!) package, indeed. Although LM317 is capable of delivering up to 37V, the circuit pictured here is limited to 25V for the sake of safety and simplicity. Any higher output voltage would require additional components and a larger heat sink. Make sure that the input voltage is at least a couple of Volts higher than the desired output. It's ok to use a trimmer if you're building a fixed-voltage supply. Problems: Follow all the safety precautions when working with mains voltage. Insulate all connections on the tr...

This is the Simple 0-30 Volts - 2-5A Variable Power Supply Circuit Diagram. This is a high quality power supply with a continuously variable stabilized output adjustable between 0 and 30VDC. the LM 723 is the heart of the power supply which drives the BD137 and then the 2N3055. The circuit provides short circuit protection. And has great stability at voltage changes. Drive the circuit with 24 Volts 3A from a transformer. the 2N3055 needs a good heat sink. 0-30 Volts - 2-5A Variable Power Supply Circuit Diagram :