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Linear DC Power Supplies - Designing & Building Custom DC Power Supplies

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DroneBot Workshop
(@dronebot-workshop)
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Two videos in one! Learn about Linear Power Supplies and then build one for your workbench.

Article with code: https://dronebotworkshop.com/linear-dc-power/

Learn how linear power supplies work, and then build one of your own. If you want to go directly to the second part, you’ll find it at 32:45.

In the first part, we will learn how linear power supplies differ from switching power supplies. We’ll take a look at the main components of a linear power supply and see how they are specified.

Then we’ll break out the solderless breadboard and hook up a positive, negative, and variable voltage regulator circuit, using a low-current transformer for safety.

Then we move on to part 2, building a small linear power supply that would look great on your workbench.

I’ll show you how I selected the components, how I hooked them up, and how I constructed and labeled the chassis. Then you’ll see how I laid out the components with safety first in mind.

And, of course, we’ll check out the resulting product, a variable DC power supply that can supply 2 - 20 VDC at up to 2.5 amps.

Here is the Table of Contents for today's (very long) video:

00:00 - Introduction
02:57 - Linear vs Switching Power Supplies
07:18 - Power Supply Components
15:41 - Rectifier Demonstration
19:34 - Voltage Regulators - Fixed Positive
25:12 - Voltage Regulators - Fixed Negative
29:15 - Voltage Regulators - Variable Positive
32:45 - Part 2 - Build a Linear Power Supply
33:56 - Parts & Prototyping
44:00 - Power Supply Hookup
49:01 - Cutting a Metal Chassis
52:30 - Layout and Design Considerations
58:09 - Labelling the Chassis
1:03:34 - Wiring & Assembly
1:07:40 - Final Product
1:10:06 - Conclusion

Although they are not as popular as switching supplies, linear power supplies do offer advantages in several situations. Learning to design and build them is an essential skill for any electronics experimenter.

Hope you enjoy the video!

Bill

"Never trust a computer you can’t throw out a window." — Steve Wozniak


   
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Ron
 Ron
(@zander)
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Which model scope is that and is there a less expensive option. I don't have any immediate need for one but have used them in HS electronics and know they can be useful but limited budget.

"Don't tell people how to do things. Tell them what to do and let them surprise you with their results.” - G.S. Patton, Gen. USA
"Never wrestle with a pig....the pig loves it and you end up covered in mud..." anon


   
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codecage
(@codecage)
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@dronebot-workshop,

What are the dimensions of the project box you used to mount everything in?  On Amazon I saw the blue enclosure shown in the video, but nothing that really looked like yours with the black top cover.

Also on Amazon, the trim pots your link pointed us to was an assortment of values, but didn't mention, that I saw, anything about 10 turn pots.

 Anyone else figured these puzzles out. 😎 

I'm also thinking about designing a PCB using Kicad.  I definitely need to keep my skills tuned in Kicad.

SteveG


   
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DroneBot Workshop
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Hi Steve

The case is a "Jameco ValuePro SY0206-R", dimensions are 6.3" x 7.8" x 2.5". I picked it up on the Canadian Amazon, but I don't see it listed on the US one (which is a bit strange, as it was shipped to me from the US).

The US Amazon has a Jameco Valuepro SY0207-R, which is a bit bigger but otherwise identical. And you can pick up the one I used directly from Jameco, it's only 10 dollars.

And yes, I did buy a kit of trimpots, you could also just order individual ones from Mouser or Digikey. 

Hope that helps!

😎

Bill

 

 

"Never trust a computer you can’t throw out a window." — Steve Wozniak


   
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JS
 JS
(@js)
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Posts: 23
 

Thanks for the linear design.. I have used that type for years-- a like an extra heater in my shop.<grin>

Switch mode power has it's place in modern design. 

Ham radio operators use linear for low noise because  high freg. artifacts may inter their IF. 

I like your design..

JS

John Spear


   
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codecage
(@codecage)
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@dronebot-workshop 

Was that 4th trim pot, to replace the 560 ohm resistor from your schematic, still a 10K like the other three, or did you use a 1K?  Seems like the 1K wouldn't need as many turns to dial it into the right value.

And is the fuse phyisical size for the AC 5x20mm?

One more question.  What are the dimensions of your perf board.  Have ordered the chassis from Jameco, but have started the Kicad layout.  I would like the PCB I'm working on to be about the same size as your perf board.

Thanks! 🤠 

SteveG


   
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DroneBot Workshop
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Topic starter  

Hi Steve

I used a 1k, and I actually put a 100 ohm resistor in series with it so that the value never got down to zero.

The fuse is a 5x20mm, it fits in the power entry module. I used a slo-blo fuse in case of power surges.

And the perfboard I used was 9x15cm.

Hope that helps!

😎

Bill

 

 

"Never trust a computer you can’t throw out a window." — Steve Wozniak


   
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Mark Bolton
(@mark-bolton)
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Posts: 106
 

Dearest Bill,

I confess I skipped your Linear DC Power Supplies presentation since I got it drilled into me in Trade School back in the 80s.

I would really love to build a proper Old School power supply but the availability of "big grunt"  transformers seems to be dwindling and they are becoming ever more (very) expensive.

I have seen projects involving Trashed Microwave Ovens and re purposing those transformers to do crazy stuff like spot welders.

I know it seems dippy but would it be possible to employ the same scrounging methodology but put a few more turns into the core to get thirty some volts? The rest of the circuitry would just be "plain sailing" but am I dreaming?

The practicality of winding such a machine makes my head hurt. The applications I have seen repurposed involve big fat copper of several turns at most, and very low voltage.

Microwave ovens grow like mushrooms on the kerb side trash collection.

Kindest Regards

 

M


   
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Mark Bolton
(@mark-bolton)
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Further I would really like to build a battery charger for my Off Grid (I know) RV which has two separate battery systems. 12 and 24 volt.  (Yeah I know) .. my last employer was involved with swimming pool chlorination systems and the transformers were beautiful toroidal ones which seemed to have 2 x 16 volts as the secondary ..cant be definite on this one but both seemed to be rated at 10 amps. A bit pitiful, but when you are all clouded over for a week or so and your batteries are getting sad? A Man becomes hopeful ( read ; desperate). Of course the proper fix is to fill the tanks with diesel and drive North (South to those of you on the wrong side of the planet 😉 ...

My point ..a good Transformer is becoming hard to find....

 

M


   
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Mark Bolton
(@mark-bolton)
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Posts: 106
 

Also a BIG warning to those of our happy community that haven't grown up around voltages that can KILL YOU!! We want you to stay with us!! Unless you have a proper appreciation of the dangers of working with Mains Voltages (or higher)  do be certain you have the proper training and experience to work with such machinery or leave it alone.

Find out exactly what you are dealing with. 

We all want to see you back again.  🙂

 

M


   
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codecage
(@codecage)
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@dronebot-workshop 

Duh!  It says right in the article that you used a 1K trim pot!  And the 100 ohm resister is a good idea, and I'll add it to my schematic that is the beginnings of the PCB.

Right now my 3D printer is chugging away at printing a template I'm going to use to layout the front panel of the project box.  I could have laid it out in thin card board and gotten done much, much faster, but somehow that just isn't as much fun as messing around with Fusion 360 to design the template.  Then exporting an STL file, slicing that and producing the g-code for the 3D printer.  And then watching a 2 hour print job!  I'll post some pics of the finished products when I'm done.

SteveG


   
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