We need DC power supply for electronic circuits for that we use either a battery or a Step-down transformer. But cost effective power supply circuit can be designed to power low current devices like LED lights or similar simple circuits. Here is a Transformerless power supply using a Resistor and a few components to make a 12 volt power supply from 230V AC. It is too simple, light weight and can power simple circuits including Transistor and IC based circuits .The circuit is highly lethal and can give a fatal shock. Therefore, it should be constructed only if you are competent to handle high volt circuits.
The circuit uses a 22K 1 Watt resistor (R1) as voltage dropper. It drops 230 volt AC to around 24 volt AC. Current is around 10 mA. This low volt AC is rectified by the diode D1 and filtered by C1. Zener diode ZD regulates this low volt AC to 12 Volt DC and the capacitor C1 makes smoothing. So around 12 volt DC is available to power the circuit. Power indicator LED will consumes around 1.5 V so 11 volt DC at 10 mA is available that is sufficient to power low current circuits. If the 22 K 1 W resistor becomes too hot, use 22 K 5 watt one.
Caution – This circuit is extremely dangerous since it carries high volt AC. So do not touch or troubleshoot when it is connected to mains. Build this circuit only if you are an experienced person to handle high volt AC.