This power supply on the LM317 chip does not require any special knowledge for assembly, and after proper installation from serviceable parts, it does not require adjustment. Despite its apparent simplicity, this unit is a reliable power source for digital devices and has built-in protection against overheating and overcurrent. The microcircuit inside itself has over twenty transistors and is a high-tech device, although from the outside it looks like an ordinary transistor.
The power supply of the circuit is designed for voltages up to 40 volts alternating current, and the output can be obtained from 1.2 to 30 volts of constant, stabilized voltage. Adjustment from minimum to maximum with a potentiometer occurs very smoothly, without jumps or dips. Output current up to 1.5 amperes. If the current consumption is not planned to exceed 250 milliamps, then a radiator is not needed. When consuming a larger load, place the microcircuit on a heat-conducting paste to a radiator with a total dissipation area of 350 - 400 or more square millimeters.The selection of a power transformer must be calculated based on the fact that the voltage at the input to the power supply should be 10 - 15% greater than what you plan to receive at the output. It is better to take the power of the supply transformer with a good margin, in order to avoid excessive overheating, and be sure to install a fuse at its input, selected according to the power, to protect against possible troubles.
To make this necessary device, we will need the following parts:
- Chip LM317 or LM317T.
- Almost any rectifier assembly or four separate diodes with a current of at least 1 ampere each.
- Capacitor C1 from 1000 μF and higher with a voltage of 50 volts, it serves to smooth out voltage surges in the supply network and the larger its capacitance, the more stable the output voltage will be.
- C2 and C4 – 0.047 uF. There is a number 104 on the capacitor cap.
- C3 – 1 µF or more with a voltage of 50 volts. This capacitor can also be used with a larger capacity to increase the stability of the output voltage.
- D5 and D6 - diodes, for example 1N4007, or any others with a current of 1 ampere or more.
- R1 – potentiometer for 10 Kom. Any type, but always a good one, otherwise the output voltage will “jump”.
- R2 – 220 Ohm, power 0.25 – 0.5 watts.
Before connecting the supply voltage to the circuit, be sure to check the correct installation and soldering of the circuit elements.
Assembling an adjustable stabilized power supply
I assembled it on a regular breadboard without any etching. I like this method because of its simplicity. Thanks to it, the circuit can be assembled in a matter of minutes.
Checking the power supply
By rotating the variable resistor you can set the desired output voltage, which is very convenient.
