Friday, 2 January 2015

need a variable dc power supply for your personal lab? make it yourself.

From the core of my heart I am Wishing you a very very Happy and prosperous new year,…..
It’s may brings you new lease to your life and gives you the best of everything………………….
After a long interval I am writing this post, actually due to work pressure, I can’t manage time to write something, in this blog I am trying to give guidance to beginners from very initial step, every one who works with projects of electronics or electrical must need a power supply to power that specified circuit,
In electronics project we mainly need de power supply, specific voltage for specific circuit, some circuit needs 5 volt supply and some circuits needs 9 or 12 volt supply, but it is difficult to arrange separate power supply device for separate voltage,
Here I am giving you the solution how to get different values of voltage from a single power supply device,
Today’s project- variable dc voltage supply for personal lab
What you need -1. A step down transformer (input 220 volt ac and output 24 volt ac)
5 general purpose diode for rectification
Capacitors-2200uf 64 volt,0.1uf,1uf 64volt
Resistors-20k,5k variable resistance,220ohm
One red led
One 1amp fuse
And the most important one is ic LM317, the
voltage regulator
Circuit diagram-
simple variable dc power supply for personal lab

How the circuit works?

The step down transformer reduces the voltage to 220 volt to 24 volt, hence the the bridge of four diodes rectify the ac output of transformer to dc, then the pulsating dc is smoothed by the capacitor, the led indicates that the power is on, then the dc voltage is fed to the LM317 is, the regulated output voltage is adjusted by the variable resistance, finally we take the output from the output terminal of the ic,
Circuit made by me-

Special note- during the process the ic becomes very hotter, so you must add a heat sink with it ,
You my use a variable resistance of 100k instead of the 5k resistance shown in the figure, the voltage variation will be slightly different,
You may use this circuit as a battery charger also,
Always keep the circuit in a plastic box, to prevent electric shock,
Thank you for reading