The transformer converts the 220V AC voltage to 30V AC. The rectifier converts the AC voltage to DC, which is then filtered using the electrolytic capacitors. The regulator (LM317) regulates the output voltage, and the output section delivers the output to the load. The circuit diagram for the Adjustable Power Supply is as follows:
With the help of two 2N3055 transistors, one LM317 Regulator IC, one BD139 transistor, and few other components, you can build your own cost-effective and customizable Adjustable Power Supply. The advantages of building your Adjustable Power Supply are numerous, and it’s an excellent way to get started with electronics.
This kind of connector can be used to switch the device from running on the battery pack to running on the power supply whenever the it is plugged in. To wire up this jack to the rest of the circuit, cut the wire coming from the positive terminal of the battery pack in half.
Another option for connecting the power supply to the electrical device is to use a substitute or dummy battery. This is anything that takes the shape of the battery and fits in the battery housing, but is used to connect the power supply to the terminals of the battery connectors on the device.
If you have just a constant voltage buck converter all you can do is adjust the voltage. That’s good enough to power all kinds of cool and interesting and awesome loads, but it's not good enough for battery charging. For battery charging you have to be able to set both the voltage and the current.
The advantages of building your Adjustable Power Supply are numerous. Firstly, it’s cost-effective. You can save a lot of money by building your own Adjustable Power Supply rather than buying one from the store. Secondly, it’s customizable. Since you are building it yourself, you can customize it according to your specific needs.