DC Amp & Voltage Variable Power Supply

we all know lm 317 and lm 338 is used for only volt regulating purpose.

But today I’m going TO show you the easiest  way to regulate volt and current with lm 338ic

Many people are confused about Amp.

Don’t worry this is a very easy fundamental formula.

The OHM law will give me the answer.

if you want to know about amps then you must divide voltage and resistance

for example if I take an input voltage of 30 volts and resistance of 10 OHMs 

if I put this Ohms's law then I am getting the output of 3 amp current.

in the same way, if my resistance is 20 ohms then I’ll get 1.5 amp current.

similarly, if the resistance is 60 ohms then I’ll get 0.500 mAh current.

I know you must be thinking about a potentiometer to increase and decrease the amp.

but wait, in this case, the potentiometer will burn instantly.

your resistance depends on your output load. 

similarly, your resistor’s wattage will increase when you increase the load of output.

to complete this project you need

 copper dot vero board, 

inductor,

 two 50k and one 5k potentiometer,

 female jumper and screw terminal,

 and heatsink and 12-volt cooling fan,

LM 338 and 7812 are, 

two PNP silicon power transistor which is tip42,

and a few resistors and LEDs.

Before making the circuit see how this diagram is working to make you understand it much better

we all know that LM338 is a volt regulator chip, which can take a load up to 5 amp.

this circuit will work very simply, where I’m using a 5k potentiometer and feedback resistor that is measuring the output volt to complete this circuit.

just think, if I can control the iC’s input current then I can also control the output current.

for this purpose I used a PNP silicon power transistor 

here it is using as a resistor to resist the output current.

which’s trigger pin is the transistor’s base pin which will be controlled by a 50k potentiometer.

I set my power supply to 15 volts and hooked the alligator clips with this board and I set my multimeter with DC voltage and connected the meter’s polarity clip with my board

if my calculation is right, then the voltage will show on the meter as I increase and decrease the volt, but if I do the same with amps then also the voltage will remain the same.

I was right. now let's give it some load, 

I connect 5 watts 0.30 ohms resistor on output and maximize the voltage, 

you can see there is no load on my power bench 

when I increase the amp from the board then my power bench takes some load.

that means this working well. 

in this case, from 38 Ic power transistor can take more load because in this current is flowing very easily so it could get hot 

you can also connect 2 of them in parallel for more powerful

full diagram

Youtube Full video