Author Topic: Is building a power supply feasible for a beginner?  (Read 7104 times)

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Offline mgysgthath

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Is building a power supply feasible for a beginner?
« on: September 25, 2016, 01:49:46 am »
In one of Dave's videos he recommended building one rather than buying one.. however at my limited skill level I wouldn't have the first clue where to begin with that.  Are there kits that are worth while?  Or should I be able to answer the question of "how" myself, before even attempting to build something like this?
 

Offline Voodoo 6

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Re: Is building a power supply feasible for a beginner?
« Reply #1 on: September 25, 2016, 02:37:03 am »
Don't see why you couldn't build your own, probably better to find a cheapo PS and practice disassembly and assembly first though. Tear it down to the board and practice identifying parts and getting the soldering down. You learn a lot by doing that, like I need flux, I need a better soldering station, lead-free solder suck, and awee crap I wish I homeowner insurance to cover the apartment complex I just burnt down. Hope this helps! Cheers!
 

Offline tautech

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Re: Is building a power supply feasible for a beginner?
« Reply #2 on: September 25, 2016, 03:46:20 am »
In one of Dave's videos he recommended building one rather than buying one.. however at my limited skill level I wouldn't have the first clue where to begin with that.  Are there kits that are worth while?  Or should I be able to answer the question of "how" myself, before even attempting to build something like this?
It's a pretty straight forward project if your needs are basic. Eventually you'll want a better PSU than one you can build but don't let that discourage you from having a go.
Set some parameters of what you'll likely need and go from there.
For most common needs a LM317 is the easiest to use and knock together without even a PCB with point to point wiring. It need be heatsinked though.

Just Google "317 diy psu" and you'll get a few hits, download the datasheet and use a "typical" application exactly as listed.

Come back to us with any questions and somebody's sure to guide you.
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Offline edpalmer42

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Re: Is building a power supply feasible for a beginner?
« Reply #3 on: September 25, 2016, 04:41:30 am »
Check out sites like instructables.com.  Find a power supply that would be useful to you and that you think you could build.  If you run into problems, you could ask questions there or here.

I don't recommend the ones that modify a computer power supply or similar.  They have mains voltage inside and things can go very wrong.  Stick to the ones that include a big transformer (i.e. linear supply) or one that uses an existing power supply as a block and adds your bits onto the output.

Ed
 

Online Johnny10

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Re: Is building a power supply feasible for a beginner?
« Reply #4 on: September 25, 2016, 05:07:21 am »
As a beginner I started with building a power supply for a sensor using two 9 volt batteries in series and a voltage regulation circuit to create an adjustable power supply.
Then later moved to a negative 40volt switch mode power supply using a laptop charger.

I have found that the motivation to build a power supply or any type circuit depends on your needs.
My very first project started with the need to build a shutter tester for vintage camera lenses.

This led to using phototransistors, resistors, diodes, voltage regulators, capacitors, oscilloscopes, DMM's, and on and on.

Look online for some simple circuits and start building!




« Last Edit: September 25, 2016, 05:16:50 am by Johnny10 »
Tektronix TDS7104, DMM4050, HP 3561A, HP 35665, Tek 2465A, HP8903B, DSA602A, Tek 7854, 7834, HP3457A, Tek 575, 576, 577 Curve Tracers, Datron 4000, Datron 4000A, Fluke 181, uTracer, HP5335A, EIP534B 20GHz Frequency Counter, TrueTime Rubidium, Sencore LC102, Tek TG506, TG501, SG503, HP8568B
 

Offline ebclr

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Re: Is building a power supply feasible for a beginner?
« Reply #5 on: September 25, 2016, 05:14:26 am »
The only value is for educational / training purpose.


http://www.instructables.com/id/Make-a-simple-12-volt-power-supply/


 

Offline nowlan

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Re: Is building a power supply feasible for a beginner?
« Reply #6 on: September 25, 2016, 05:29:13 am »
Plug pack & lm371 are a good start for learning purposes.

Ultimately you would want something that has current limiting to avoid oopsies.

The kit in Daves video would cost more than Chinese lab psu.
 

Offline jonovid

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Re: Is building a power supply feasible for a beginner?
« Reply #7 on: September 25, 2016, 07:06:30 am »
made this recently. moded a 1.5amp Chinese Power Supply Module,  put it in a box with a 240v/ 25v transformer from an old Radio/CD player, add a  Auto 15w 24v Auto bolb in series on the 1 amp side for a overload   3 pin AC IEC socket
« Last Edit: September 25, 2016, 11:05:14 am by jonovid »
Hobby of evil genius      basic knowledge of electronics
 

Offline DTJ

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Re: Is building a power supply feasible for a beginner?
« Reply #8 on: September 25, 2016, 07:54:54 am »
If you are concerned about working with mains (which can & will kill) look at making a power supply that runs from a wall wart or surplus printer or laptop power supply.

Maybe check out eBay and see what the offerings are.
 
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Offline Kappes Buur

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Re: Is building a power supply feasible for a beginner?
« Reply #9 on: September 25, 2016, 08:46:49 am »
In one of Dave's videos he recommended building one rather than buying one.. however at my limited skill level I wouldn't have the first clue where to begin with that.  Are there kits that are worth while?  Or should I be able to answer the question of "how" myself, before even attempting to build something like this?

This looks more complicated than it really is.

If you do not fancy to build the whole thing, it is simple enough to just extract one of them.
 

Offline ebclr

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Re: Is building a power supply feasible for a beginner?
« Reply #10 on: September 25, 2016, 09:36:40 am »
If you know how to solder and want to start on electronic, It's easy, and it's a nice step to learn, Try I still remember my 1st circuit from 40 years ago.

It's a small step by is a step
 

Offline R005T3r

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Re: Is building a power supply feasible for a beginner?
« Reply #11 on: September 25, 2016, 06:30:14 pm »
I've built my PSU long time ago, but given the importance of the tool for other projects I've switched to an Agilent one. Actually, it was the first instrument I've ever bought! Anyway, yes, it's very appropriate as first project, because you will see with your eyes what are the limitations and the problems that will help you decide to buy a decent one.
 

Offline eventhorizon

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Re: Is building a power supply feasible for a beginner?
« Reply #12 on: September 25, 2016, 07:24:34 pm »
I am a beginner and I am working on one that uses a 12v wall wart that may be changed out to a laptop charger when all said and done.  The plan is to use 2 lm317s (one for current and one for voltage) and pots for the adjust.  If you want I can share what I have and the weird things im seeing and we can work it out together and try to learn something and when all else fails come here for advice.
 

Offline Kleinstein

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Re: Is building a power supply feasible for a beginner?
« Reply #13 on: September 25, 2016, 08:14:14 pm »
Starting with something like an old laptop supply or similar is a good idea. As a beginner one should be careful with mains, unless you know well about this (e.g. as a trained electrician but new to electronics).

A supply is a reasonable good project as a beginner, though it can get quite involved if you want a good one and really understand it. It can start easy, like a LM317 (for a adjustable voltage). One can learn quite a lot, but should usually start small for the beginning. Much less magic smoke in an 1 A supply than in a 10 A version. Nothing is wrong to have an additional version with limited capabilities (e.g. fixed current limit or limited voltage range).

Using two lm317 to get voltage and current control is a bad idea however. Better go for an old LM723 and a power transistor.
 

Offline eventhorizon

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Re: Is building a power supply feasible for a beginner?
« Reply #14 on: September 25, 2016, 08:38:23 pm »
Using two lm317 to get voltage and current control is a bad idea however. Better go for an old LM723 and a power transistor.

Can you explain what you mean by bad idea?  Are we talking efficiency because I know about that and I understand that I would be creating a space heater if I do a 12 or 18v to 5v 1a.  Or is this ability to control that you are talking about?

 
 

Offline joeqsmith

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Re: Is building a power supply feasible for a beginner?
« Reply #15 on: September 26, 2016, 01:43:55 am »
Quote
Is building a power supply feasible for a beginner?

I don't see why not assuming you have the skills to do it.  You don't need to design anything.  Maybe just a text book example.   I made several cobbled up supplies when I was starting out.   I built this linear supply in the early 80s and still use it.  It's the first thing I ever built using a microcontroller.   It's based on the old Motorola MC1566.  Programmable from RS-232 and even has a separate voltage input so you can read back current, voltage and one other voltage probe.    Keypad was from an old girl friend's telephone.  The plastic face came from a friend of mine who worked at a molding company.   This thing can output up to 10A.  The transformer came from a Sperry UNIVAC terminal I had scrapped out! 

So sure, if a person has the knack for it, why not.
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline perieanuo

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Re: Is building a power supply feasible for a beginner?
« Reply #16 on: September 26, 2016, 01:08:25 pm »
Using two lm317 to get voltage and current control is a bad idea however. Better go for an old LM723 and a power transistor.

Can you explain what you mean by bad idea?  Are we talking efficiency because I know about that and I understand that I would be creating a space heater if I do a 12 or 18v to 5v 1a.  Or is this ability to control that you are talking about?
Lm723 rules.you can't fry it eve if you want.317 dies sometime for a little glitch.go with 723 I built several they works for years.just put 2 transistors and capacitors 0.1 on vcc vdd vout and you're on.Regards,ovidiu


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Offline setq

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Re: Is building a power supply feasible for a beginner?
« Reply #17 on: September 26, 2016, 01:34:37 pm »
Please don't build an LM317 based solution. Go for the LM723 and pass transistors suggested elsewhere in this thread.

An illustration why including a power supply design effort:

1. I want a 1.2-20v DC power supply with an LM317 that can shift an amp. Perfect spec.
2. Build an unregulated DC supply that shifts out the dropout voltage plus the max voltage plus a couple of volts to deal with capacitor ripple of 20+3+2 volts = 25v dc. An 18v AC transformer will do the job!
3. Whop the LM317 on the front end.
4. Think "hey i'll set this to 3.3v for an arduino project and I need 1A out - full whack"

Quite reasonable yes?

Well no it isn't.

The transformer isn't an 18v one. It's higher than that. More like 20v so it remains in spec when under load. So that's 28v DC.

The LM317 has to drop about 24v at half an amp. P=IE, so it has to shift 24W of power. The LM317 can shift, when well heatsunk with a bastard heatsink from hell just under half that. Bye bye regulator. They do explode as well. I've done it a couple of times.

The same story with a 2n3055 pass transistor is dissipation of 115W.

Hence LM723+2n3055 if you're going to do this. LM317 is only suitable for light loads. Not bench supplies, even your first one.

I haven't included mains transients here either which increase dissipation, dead short conditions etc. The LM723 has a programmable current limit so you can protect the rest of the circuit or the power supply in an overload condition.

Lots of design information here to explain this: http://artofelectronics.net/wp-content/uploads/2016/02/AoE3_chapter9.pdf

But yes, DO build your own power supply. Just don't copy it from some idiots on the Internet. Learn about it then understand it, then build your own design confidently.
« Last Edit: September 26, 2016, 01:37:01 pm by setq »
 

Offline Kleinstein

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Re: Is building a power supply feasible for a beginner?
« Reply #18 on: September 26, 2016, 06:32:29 pm »
The LM317 is OK for a simple supply without adjustable current limit. It just is really hard to add an adjustable current limit. The idea you sometimes find with a second 317 is just not really working. Cross over is really poor. In addition the LM317 has really limited power dissipation, so its not good if more than a 10 V difference is needed. The LM317 is made for an internal supply with fixed load, not for something like a lab supply.

The LM723 is not perfect, but good enough for a supply with adjustable current limiting. Also keep in mind that the maximum power dissipation for transistors is for a kind of perfect heat sink on a cold day (e.g. 25 C case) - so something like half that value is realistic. Some de-rating also applies to the 317.
 

Offline george.b

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Re: Is building a power supply feasible for a beginner?
« Reply #19 on: September 27, 2016, 06:36:02 am »
Meh, using an LM317 for your first "bench" power supply is fine. That's what my first adjustable power supply was based off, anyways. Downsides, as already mentioned, are a lack of current limit adjustment (unless you kludge two of them together, not really an elegant solution) and power dissipation (although there are TO3 parts).
It does have thermal protection, though. I don't remember ever getting one to explode - except that one time when I got counterfeit ones, watch out for that.

Just don't expect much from it. Use it for light loads, just having an adjustable voltage source to begin with is already something, better than nothing. It's crappy, but it's something.



The "how" part is, at least partially, answered in the datasheet.

After you build it and it works and you get proud of yourself for it, then you could design another, better one, maybe even cannibalize the first one for parts.

That's my opinion anyways.
 

Online Gyro

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Re: Is building a power supply feasible for a beginner?
« Reply #20 on: September 27, 2016, 09:03:26 am »
Another vote for the 723 approach. You'll learn more and there are lots of app circuits in the datasheet (and elsewhere). Most importantly you can implement Proper current limiting, a most valuable feature for beginners, and used by most sensible people, for bringing up prototypes. You'll probably recoup any cost difference quite quickly in non-fried components.

For a beginner, using a chunky TO3 package pass transtor (not necessarily a 2N3055, there are darlingtons too) makes it a lot easier to dump heat into the heatsink, due to the much larger interface area, It's also very easy to share the load between a couple of transistors. Optimally thermal mounting of a TO220 package at high dissipation is full of gotchas.
Chris

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Offline setq

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Re: Is building a power supply feasible for a beginner?
« Reply #21 on: September 27, 2016, 09:39:16 am »
Learning is the important bit. Agreed.

I fixed the stickman above who dropped more than 12W off his LM317

 
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Offline Voodoo 6

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Re: Is building a power supply feasible for a beginner?
« Reply #22 on: September 27, 2016, 09:45:32 am »
Not quite sure why folks are trying to peddle wares in threads. Op grab a random discarded electronic item and go to town. Tear it down and learn before you build something. You will learn as you go. If the art is for you you can progress further, and separate the chaff from the wheat.
 

Offline just5554

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Re: Is building a power supply feasible for a beginner?
« Reply #23 on: September 27, 2016, 11:39:08 am »
I'm also now building my 3rd power supply, but now I want it to be more efficient, so instead of linear I want to use switching power supply and buck converter, but can I use f.e. this power supply with buck converter? https://www.aliexpress.com/item/Universal-24V-5A-120W-Regulated-Switching-Power-Supply-Transformer-100-240V-AC-to-DC-For-LED/32606322171.html?spm=2114.13010308.0.87.T9KbHB
 

Offline Cliff Matthews

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Re: Is building a power supply feasible for a beginner?
« Reply #24 on: September 27, 2016, 01:19:56 pm »
Not quite sure why folks are trying to peddle wares in threads. Op grab a random discarded electronic item and go to town. Tear it down and learn before you build something. You will learn as you go. If the art is for you you can progress further, and separate the chaff from the wheat.
Peddler's gain by peddling - I fail to see it aplenty on this forum..  :-// Do you refer to links offered as help suggestion's?
 
 


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