Best DC power supply 3Amp LM317T

There is the high quality power supply to provide high current 3A. And still adjust voltage in steps from 3V, 6V, 9V, 12V. adjust voltage is continuous 1.25V to 20V. Using LM317T and 2N3055 are main parts so easy to made and cheap.

Friends would known the power supply as well. Because you must use in various circuit experiment. It originally had a small supply current, when found projects that uses lot of current. Such as an audio amplifier circuit so provide current is not enough.
This project can help you. Because of provide high current 3A. And still adjust voltage in steps from 3V, 6V, 9V, 12V. adjust voltage is continuous. And you do not have to worry. This creates a simple and economical. If interested, please read on.

How it works
In the circuit below can be seen that, when opening switch S1 is current through the transformer. To convert from 220V AC to 18V, then through diode bridge rectifier BD1. But is a DC supply that still not smooth. Then, a filter capacitor C1 serves electricity, out of BD1 to be more smooth with the LED1 to show that power is supplied to already.
When the filter current is smooth on one order. The current will through the regulator circuit that the main components are IC1(LM317T) and Q1(2N3055).
-IC1 is the regulator IC number : LM317T.
-Q1 is power transistor NPN type number : 2N3055.

Before the DC volt through IC1 would have C2 served filter noise off. When we adjust the variable resistor VR1 or rotary switches S3 twist choose it. Will cause changes the voltage at the ADJ pin and OUT pin of IC1. Which will be resulting the voltage drop across the base pin and the emitter pin of transistor Q1 changes. Makes the voltage on the connector is changed accordingly. And before the voltage is applied to current C3 filter to smooth again.
Detail see in circuit image.

NE555 based inductivty meter

Hi!
This blog is about new inductivity meter based on a NE555.

For my experiments with switch mode converters, I needed a simple way to compare inductivities of coils.
Since I don't have a multimeter which can do inductivity measurement (but I have a really great multimeter, more infos perhaps in the next blog), I decided to build one.

And this is the schematic of it:

A NE555 works in its most simple rectangle osciallation configuration.
In this mode, the duty-cycle should be around 50%, but this depends on the load on pin 3.
Over the amplifying transistor Q1 the AC is given on an LC circuit.

It oscillates a freqency given by the equation:

This oscillating waves are amplified by Q2 and frequency is converted into a voltage by the RC-network of C3 and the ampmeter.
Due to the capacity of both C3 and C2 being constant, the current through the ampmeter is defined by the inductivity.