we will build a linear power supply that can output 30v 3amps
.This was my first ever build power supply and i am happy about the results so i decided to share it with a complete guide
Step 1: Knowing What You Are Building
We are going to build a power supply ,yeey,
but there are many types out there in the market , so the question is : Is this power supply good ? why?
well its yes and this is why : there are 3 major types of power supplys :
-unregulated power supply
-linear power supply
-and switching power supply
i will not get in details and bore you but keep this notes in minds:
Unregulated power supply is easy to make but the output voltage have so much noise so its bad option for analogue circuit .
Switching power supply is difficult to make and it have a complex diagram .
But what we are going to build is a linear power supply. its easy to make , have a clear output voltage but 50% efficiency , but we cant be so picky since this is our first power supply right?
now lets get the the build
Step 2: Tools and Materials
since we cant make stuff from thin air ( :'( ) we need to get some parts and some tools , luckily i got you covered .
This is the list for what we need :
1-a 30v 3A kit from ali express; this way you don't have to worry about missing up the diagram, the circuit is clean and lovely .
2-a transformer : 24 AC/3 A ( make sure your transformer can output at least 2 amps of current)
3-a digital volt and amp meter : since we are going to make a variable power supply at least you want to see the voltage you are setting right?
4-socket : used to connect the transformer to main ac voltage
5-a fan : the keit get really hot so we need to cool it down with a fan
6-heat sink ; we need to cool down the resistors in the circuit so it does not melt internally and fail
7-some woods for the frame
8-hot glue gun and a screws for wood
9-and a on/off switch to turn it on and off when needed
Step 3: Undrestanding the Diagram of Your Kit
since we are not going to build it from scratch at least we have to learn how it works right?
well i will give you a simple walk throw to how it works.
Open the pdf file and go to last page ; that is the diagram of the kit : but it is missing the 24 V regulator.
first your 230AC voltage ( or 110) gets transformed to 24 ac through the transformer , then it runs through a bridge rectifier (4 diodes) and the turned into DC 33.6 volts (24*√2=33.6). Now part of the current will go to the 24 fans through a 24 regulator the re rest to a transistor Q4 (see diagram).
transistors work with current applied to its bass we can change it using Q2 which is a transistor too.
we control Q2 with 4 TL081 ( amplifiers :op) and we can select the voltage and the current limit using a 2 potentiometres .
the is a current limiting led which lights up when the current exceeded the limit current set but the pot , when the led lights you will notice that the voltage will dope down.
now lets build it .
i added a similar diagram that contained a mosfet in place of the transistor but to be honest that it the only difference and the rest of the diagram is the same but i found it cleaner and easier to read
Step 4: Build and Test the Kit
after soldering the kit hook a multi meter to the output and turn the voltage pot the the right it the voltage value is 0 you are ready to do the rest if not you need to remove the off set how?
well easy ; you will find a trim pot which is the blue pot in the kit ( the only blue part so you cant miss it)
turn it to the left or to the right until the voltage gets to 0. you are ready now for the next step.
(use the pdf in the last step to guide you more )
Step 5: Hook Your Digital Multi Meter
now use this diagram to connect your multimeter and make sure to not short circuit it and burn it like mine: i burned the amp measuring parts so now i can only use it and a voltmeter , well at least i can see the set voltage
Step 6: Make the Box
now since the electronics works fine: use plastic and wood for the frame , i don't advise you to use metal since its conductive and if you don't isolate it well you will burn down the circuit or in works case electrocute your self.
make sure to leave some holes for the fan.
Step 7: CONGRATS
congrats you did it, i hope you found this helpful and if you need any help you can ask me here on my facebook page:
have fun in your next project