Today we will learn how to make a small power supply unit for your small projects.
LM317 will the good choice for low current power supply.
Lm317 provides variable output voltage which is depending upon the value of resistance is actually connected with it, so if it is a potentiometer then you can adjust the potentiometer and get variable Voltage, even you can get any fix Voltage as well by using a constant value resistor instead of potentiometer.
So let's start making a small lab bench power supply using LM317
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Step 1: Things You Need
1x 12v Power adapter/supply : https://www.utsource.net/itm/p/9221236.html
510 ohm Resistor or something equivalent to it ( i am using three resistor in series to make it 520ohm in total) :
1x 10k potentiometer : https://www.utsource.net/itm/p/8038955.html
Few jumpers : https://www.utsource.net/itm/p/9221310.html
1x multipurpose PCB & tools to solder components on Pcb :
1x 0.1mF ceramic capacitor : https://www.utsource.net/itm/p/8036440.html
1x 1mF dyelectric capacitor : https://www.utsource.net/itm/p/8045304.html
mini Voltmeter module : https://www.utsource.net/itm/p/8288401.html
Step 2: Put Lm317 on Breadboard
Put LM317 on the Breadboard and connect the power to the power rails of Breadboard, for me the green wire is +12v & yellow wire is GND.
Step 3: Connect Input to LM317
As you can see the image connect the +12v (green wire) to the 3rd or input pin of the LM317 as shown and for this connection i used brown wire here.
Step 4: Connect Resistor
Now we need to connect Resistor between pin 1 & pin 2 and resistance value will be 510ohm, since i was not having 510 ohm so i used 3 resistance in series to make it 510 ohm and connected between pin 1 (adj pin ) & pin 2 ( out pin).
Step 5: Connect Potentiometer
After completing above step just get a Potentiometer ( 10k ) and attach one ned of potentiometer to pin 1 of Lm317 (adj pin) and attach another end of potentiometer to GND of power supply
Step 6: Connect 0.1uF Cap
To filter/make stable the power supply properly use 0.1uF between +12v & GND as i did it in image.
Note: capacitor is very important please don't miss it.
Step 7: Add 1uF CAP
After above step please add one more Cap ( 1 uF ) between pin 2 of lm317 ( out pin ) & GND of power supply.
Step 8: Getting Output
So after connecting everything According to this given schmatics, you can connect to output wires to get output ,
+Ve wires can be connected to pin 2 of lm317 ( out pin )
-ve (gnd) wire can be directly connected to gnd of the supply we are using.
So +ve & -ve wires we got , which are our variable Voltage output and when we regulate the potentiometer the output voltage will change according to that.
Step 9: Add a Mini Voltmeter
For displaying the voltage lets add a mini voltmeter.
So in this voltmeter there are three wires only ,
One is Vcc/+ve for power so connect to +ve of power supply
Other one is Gnd/-ve for providing gnd to voltmeter so connect it to gnd.
And please check the power requirements of your mini voltmeter before connecting, the one i had will work with 12 v .
And the other remaining wire is for sensing the voltage level so that wire will be connected to out (pin 2 on lm317) .
And some mini voltmeter even come with two wires so in that case you can skip the Vcc wire so it will have only gnd wire and sensing wire so connect those two only.
Step 10: Check the Output
After doing everything mentioned above, turn on the power and rotate potentiometer and you will see the voltage value changing on your mini voltmeter.
Even now you can use Out pin of Lm317 for output & gnd wire and together these will be used for any output device like Led, motor.
Step 11: Create a Enclosure Box
Create a enclosure box and put everything in it and take out only Vout & gnd wire for power and add holes of potentiometer & mini voltmeter , and add a knob to potentiometer.
Step 12: Final Step
Attach any output to the Vout & gnd wires we got and rotate potentiometer to get the voltage output of your choice & it will work like charm.