12 Volt DC Power Supply project

Thread Starter

juantorres0704

Joined Nov 20, 2017
1
power supply.PNG powersupply schematic.PNG

Hey guys, I need help with this project. Can someone confirm if I'm using the right components to meet the project specifications? Also, this is my first time using Multisim so I have no idea if the schematic that I designed is right or not. can anyone help me identify schematic errors? Your help and suggestions are very welcome. I need help designing this 12 volt DC power supply. I have attached the project specifications along with the schematic that i have designed.
 

bertus

Joined Apr 5, 2008
20,870
Hello,

Why do you use the high voltage version of the LM317?
What is the output voltage of the transformer you use?
Why is there no buffer capacitor?

Have a look at the attached PDF for calculating R1 in your schematic, as it has the wrong value.

Bertus
 

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Picbuster

Joined Dec 2, 2013
1,022
As indicated by Alberthall it will not work. ( you LM does not like you anymore when power is applied)
look at the data sheets of the components used.
ripple is depending on current, frequency, capacitor ( at output) and single or double phase rectifier.
Google ripple voltage and you will find your answers to finish your design.

Good luck.
Picbuster
 

WBahn

Joined Mar 31, 2012
26,277
Aside from the issues already mentioned, the bottom side of your two capacitors appear to be connected to each other, but not to ground. I find it unlikely that Multisim would put connection dots on three-way connections but not on four-way ones.

Instead of letting someone just do your work for you and tell you what capacitor you should use for C5, you should DESIGN your supply and determine what that value should be. Consider what you are going to say to your instructor when they ask you why you used that particular value. I don't think, "That's the value some guy on the internet told me to use," is going to go over very well. Unfortunately, some of our members don't seem to grasp that concept very well. Instead, you want to be able to walk your instructor through the issues that are involved, how the presences of C5 is intended to address them, and describe how you determine how large it needed to be in order to do so.
 

AlbertHall

Joined Jun 4, 2014
10,540
Aside from the issues already mentioned, the bottom side of your two capacitors appear to be connected to each other, but not to ground. I find it unlikely that Multisim would put connection dots on three-way connections but not on four-way ones.

Instead of letting someone just do your work for you and tell you what capacitor you should use for C5, you should DESIGN your supply and determine what that value should be. Consider what you are going to say to your instructor when they ask you why you used that particular value. I don't think, "That's the value some guy on the internet told me to use," is going to go over very well. Unfortunately, some of our members don't seem to grasp that concept very well. Instead, you want to be able to walk your instructor through the issues that are involved, how the presences of C5 is intended to address them, and describe how you determine how large it needed to be in order to do so.
Mind, I like the PCB inductor in series with the multimeter.
 

dl324

Joined Mar 30, 2015
11,845
Also, this is my first time using Multisim so I have no idea if the schematic that I designed is right or not.
Learn how to use Multisim. When its brain dead autorouter offers to draw circuitous routes for you, force it to make them straight.

You have a simulator. Simulate the circuit and start fixing the many problems in your design.

There's not much challenge in designing a power supply for the specifications given. The voltage regulator is doing most of the work...
 

WBahn

Joined Mar 31, 2012
26,277
For the components given, namely the two resistors used to set the output voltage, what will the output voltage try to be?

If you spec is for a fixed 12 V output, then one question that can be asked is why you are using a variable voltage regulator at all. Why not use a 12 V regulator? Is it not reasonable to expect that a fixed regular will likely provide better performance at it's targeted output voltage than a variable regulator is likely to achieve at that same voltage, given that it must also be designed to work reasonably well over a wide range of output voltages?

Just how much effort have YOU put into this design? It appears that you just copied something from someplace on the internet and haven't even attempted to simulate it.
 

WBahn

Joined Mar 31, 2012
26,277
Mind, I like the PCB inductor in series with the multimeter.
Yeah, I know what you mean.

Even as a student using CAD tools for the first time, I took pains to make the schematic presentable. That probably stems from the fact that all of my schematic (or other) drawing experience before that was by hand, so I saw no reason to accept computer-based drawings that were so inferior to what was deemed acceptable for hand-drawn ones. But today the attitude seems to be that whatever the computer regurgitates must be good enough since, after all, a computer did it and we all know that computers do everything better than mere humans can.
 

bertus

Joined Apr 5, 2008
20,870
Hello,

That are already quite some posts, but no sign of the TS.
He could have a look at the datasheets of some regulators (if he is allowed to use regulator chips).

Bertus
 
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