In this post, I have explained how to build good rectifier circuit to convert 230V AC(This depends on your regional distribution voltage. Eg: 120V in US) power supply into 5V DC power supply. This type of circuit is essential for electrical students when they have to design circuits with microcontrollers and other 5V power supply(VCC) required ICs. This is the circuit diagram.
Lets go from left to right of the circuit. Here I have used 230V to 9V transformer. It has a 300ma rated current. In micrtocontroller based projects we do not need 300ma. But these are the commonly available transformers in the market. Follow my post to get more detail about selecting a suitable transformer.
Then common full rectifier circuit with four 1N4002 diodes. I think that i do not need to explain how does this bridge work.
470uF capacitor has been connected between the output terminals of the bridge. This capacitor is very important. Without this, there is a significant change in power output. It increases the supply voltage to the rectifier and make smooth the waveform. If you connect a LED to a microcontroller pin and supply power without this cap most possibly you will see flickers.Other caps also do the same work.
Finally about the regulator. Regulators are designed to supply required voltage without fluctuations. That means we do not need to use regulators with DC power supply. But most of us use these regulators. Why? We use them to reduce the voltage to a desired value. Here we have used AC supply and the regulator does both of those things. It supplies a constant voltage and reduces 9V to 5V.
This is a good time to explain how select a regulator from the market for this type of project. Normally last digits of the regulator indicates the out put voltage. Eg: 7805 : 5V, 7806 : 6V, 7809 : 9V. Regulators with wide range of voltages available in the market. Normally input voltage should be 2V graeter than the output voltage. If you need to regulate negative voltage you can use 79XX series.
