How to make variable power supply using lm317 | #newvideo2021 #newvideo #voltageregulator #variablepowersupply #diy #lm317 #bd139 #tip3055 This Project is to make a simple variable Power supply in LOW cost. Mager Components LM317-: The LM317 is an adjustable 3-terminal positive voltage regulator capable of supplying different DC voltage outputs other than the fixed voltage power supply of +5 or +12 volts or as a variable output voltage from a few volts up to some maximum value all with currents of about 1.5 a mperes. BD139 Transistor:- BD139 is an NPN transistor hence the collector and emitter will be left open (Reverse biased) when the base pin is held at the ground and will be closed (Forward biased) when a signal is provided to the base pin BD139 has a gain value of 40 to 160, this value determines the amplification capacity of the transistor. The maximum amount of current that could flow through the Collector pin is 1.5A, hence we cannot connect loads that consume more