Linear DC Power Supplies - Designing & Building Custom DC Power Supplies
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- Опубликовано: 1 июн 2024
- Two videos in one! Learn about Linear Power Supplies and then build one for your workbench.
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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 
Хобби
![Roddy Ricch - Survivors Remorse [Official Music Video]](http://i.ytimg.com/vi/J5IeFzr2GgE/mqdefault.jpg)
Hi everyone - It's come to my attention that there has been someone masquerading as myself, responding to some comments here with a link to a Telegram chat to win a prize from me. THIS IS A SCAM, I am not holding a contest, nor do I have a Telegram account. PLEASE DO NOT RESPOND TO THESE MESSAGES!!
It's happening on a lot of my videos, I'm taking steps to remove them manually, but as I have 162 videos, it will take some time. If you do run across a suspicious comment, I would appreciate you letting me know at info@dronebotworkshop.com.
Thanks!
Bill (The real one!)
It's a bit of a problem with many Western practical and news same scan on hundreds of YT videos. No one who want to talk privately will ask you to use telegram and be suspicious of links in chat. Love your Vids respect bro
The quality of the project and the clarity of the tutorial makes this channel the best for electronics. Thank you for imparting this wisdom to us earthlings.
A great instructor indeed.
Professional Power Supply, the last power supply I built, was some 50 years ago as an apprentice in a TV/Radio repair shop, now retired I want to build one of these, in place of the commercial P/S I use, your calmness on explaining, reminded me of the Engineer that taught me Electronics & Repair, your doing a wonderful job, I'm now a subscriber.
I've watched perhaps 20 of your videos, and, if I were someone wanting to produce informational or how-to videos, (or if I speak with anyone planning to pursue it,) I would reference them to this particular video. I would go on about what I like specifically, but this video has it all. Not that your others lack, it's just that- within the scope of a "simple" power supply, your example of a YT producer wouldn't get lost on someone who is not interested in electronics, and they could profit from your absolutely fantastic way of filming, lighting, recording audio, adding effects, linking to other sources, consistency, and so, so much more. I know this comes a year after you posted it, but I've saved it for both the reference for others and because I definitely will be building this as my first full scratch system build. What a great job you continue to do!!! Thanks so much for all your hard work!!!
I am so grateful for your videos. Im a self taught tinker-er and have been repurposing electrical components for a couple years now and am learning more from you than pricey course videos I've used. Thank you sir! Im a loyal fan.
Hello! Retired mechanical engineer here. When I went through school we didn't quite use a kite and a key for a power supply but electronics instruction in the ME curriculum was pretty preliminary and not very practical. I vaguely remember a semester of Kirkoff's loops but was glad when it was over. However in my declining years I've taken a real interest in small electronics projects and your videos have been a terrific aid in my endeavors. My sincere thanks for all your efforts. Wonderfully understandable and straightforward!!
I have built so many of these through the years. The 78xx series and the LM317 made it simple and you could always get a decent transformer out of old electronics. I still have one I built in 89 as part of my breadboard setup. It has 5v, 12v and a variable section similar to what you built. The whole thing was built into a metal and wood sided box I had from an old audio amp.
I really appreciate these courses. He has a lot of information and makes things very interesting to learn and helps fill in the gaps.
I have a Chinese DCDC Boost/Buck converter coming in today and this video releases at the same time! I'm a beginner and this was incredibly helpfuL!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Seriously awesome thank you!
An excellent video, from which even experienced builders can gain tips; I did. Thank you. A few points that I noted... 1) I do not recall that you discussed the additional overhead voltage needed by the voltage regulator. Lots of people just add 1.5 volts, above the voltage regulator's output rating. However, a close inspection of the data sheet reveals that a minimum of 3V of additional voltage is required for the best ripple rejection. 2) The small, rectangular trim pots are not intended for continuous use. They are meant to be set, once, for some calibration factor and not turned, again, except for fresh calibrations. That is the way that you are employing them; this is just a tip for inexperienced builders. They will fail, quickly, with regular use. Use a knob-style pot, for user adjustments. 3) Using resistor dividers to create additional output voltages limits the current supplied by those outputs to the current carrying ability of the resistors used, not the regulated voltage supplied. Meaning, the LD1085 can supply 3A, but the trim pots that you used can only carry a fraction of that. By extension, that means that a calculation based on the trim pots wattage rating will be necessary to determine the current that can be sourced for the additional outputs. Or, if you intend to purchase resistors for the purpose of carrying the full 3A, you will need to make a similar calculation to determine the wattage rating they will needed. 4) The style of Volt/Amp Meter that you are using has a known minor issue... They source there voltage from the DUT circuit. This is called "burden voltage." Therefore, they do not display the exact voltage of the DUT. There are RUclips videos on this problem and how to correct the wiring. 5) Most of us now own inkjet printers and they do not do as well for creating labels. So, another easy method for labeling is to create the label in your favorite draw program and, once laid out properly, print it onto white paper as a mirror image. You can find the mirror image printout setting in the file/print properties function. Then, take the paper to a big-box office supply store and have them use their laserjet printer to copy it onto clear film transparency paper. Because you printed a reverse image, the tender ink will be behind the clear film and protected, once you orient the print to read correctly from the front. Cheers!
Very helpful observations. The tip about printing onto clear mylar is very useful!
@@douglas2lee929 Thank you!
You make many good points, but with regard to (3), I don't think you have a correct understanding about how the circuit is (probably!) wired. Unfortunately, no schematic of the full circuit is provided (that I recall), but I believe that the 4-way switch is used to select one of four voltage divider pairs to set the output voltage, rather than having the supply current passing directly _through_ these pots. Three of these dividers are provided by the trimpots on the circuit board, and the one for user-adjustable output voltage is composed of the panel pot plus a trimmer on the circuit board (used to optimize voltage range). All these dividers are sourced from the output of the regulator. The wipers/set point voltages from these pots feed into the points on the switch, with the centre pin of the switch connected to the adjustment pin on the regulator. Therefore, the circuit *is* capable of providing full power to the external load regardless of which voltage divider is used, since in all cases the regulator output is directly connected to the positive binding post.
Thanks for the other observations and suggestions! I especially like the idea of using clear film transparency paper and a laser printer to label the chassis. The only thing unclear about this is how to mount the transparency onto the case, but I suppose something like 3M Super77 spray adhesive would do the job. Is that what you use?
@@andreafalconiero9089 "with regard to (3), I don't think you have a correct understanding about how the circuit is (probably!) wired." That is quite possible. "The only thing unclear about this is how to mount the transparency onto the case, but I suppose something like 3M Super77 spray adhesive would do the job. Is that what you use?" I do use spray adhesive and I like it very much. But, for this application, I believe it could be seen through the clear plastic. So, I would use a different approach... I would make the label to be slightly smaller than the entire size of the face plate. I would cut very accurate holes for the switches/pots, etc. I would remove all the knobs/etc. I would then apply the label to the face plate and use the hardware/nuts/etc. to secure the label in the middle of the plate. I would finish the edges by applying some type of decorative tape. But, each individual should use their creative instincts and work with the supplies and tools that they have. It should be fun. Cheers!
@@t1d100 Thanks for the reply.
I like your suggestion for mounting the transparency, but thought of a couple of others as well:
1) If the spray adhesive would mess up the appearance of the background, it might be possible to fix the problem using a paint layer on top of the printing. I would try applying an opaque spray paint onto the printed side, and then use spray adhesive to bond _that_ to the case. As long as the paint layer doesn't separate from the transparency film, it should look good and both the adhesive and the case itself would be hidden. This could work particularly well if one was re-using an old case with unwanted holes, etc., since these too would be covered over.
2) There are quite a few project cases that have a separate plate for the front and rear panels that slides into a groove on the case. By using one of those, it should be easy to keep the transparency in place without using any adhesive and/or paint, just by setting it loosely within the frame and relying on the knobs, meters, etc. to hold it in position, as you suggested.
I’ve been watching so many diy videos and I think them most of them are made by Indians or bangles. No commentary, very little description, and the same washed up stock RUclips techno music. Then I found drone bot workshop and everything is so clear step by step. No need to screen shot and zoom in on parts of the video to try and figure what things are on Google. I come here and leave here with a sense of having learned things, and knowing I can do it. I’m almost 40 and just getting into electronics. Please don’t change your style. 👍😎👍
ESCARGENCY
I am just learning electronics too and he has every thumbs up
Just the shear fact that this information is free yet alone masterfully compiled and explained…wow. You’re amazing!
This video is properly well produced.
Well done! And thank you.
Finally an electrical engineering channel that doesn’t have an impossible to understand accent, incredibly poor explanations and a camera that flies all over the place
Thanks! Again another great video. I almost skipped the first part then saw your test transformer setup and realized I want to build that too. Thanks again
Thanks Kyle, glad to hear that you watched the whole thing!
This was a seriously great tutorial. Personally I would have watched an extended series that included preparing the chassis, soldering the perfboard - there was just so much good info in there about how to approach a project like this.
❤
I'm an EET and gleaned quite a bit of knowledge from this video. Thank you! You're quite meticulous in your methodology. Much appreciated. Thanks again.
I've built linear and PWM power supplies over the years. I try to keep my circuits running cool. I believe that this project would benefit from a large heat sink on the regulator IC. The amount of heat can build up fast and catch you off guard. With plenty of open space on the back of the case looks like a good location for the heat sink. It is also possible with an op amp and some other components to get the low end of the voltage regulation down to 0 volts. If you don't care about the circuit being more complicated current regulation could also be added. For a simple Bench top Power supply this is an excellent project and I would highly recommend it. I think I would go with an electrolytic cap on the output as I have seen too many of the tantalum caps short when they go bad. I wish people would have given me feedback on some of my projects as it is sometimes easy to overlook something when designing and making a project. I love this channel.
sooo... I've just spent an hour and a bit watching this and I am completely and utterly blown away!
Blown away by the sheer amount of great information!
Blown away by the easy to follow way it is presented!
Blown away by the way you have explained everything, and I do mean EVERYTHING! So many times I watch a video and they skip over explaining the thinking behind the little things, but not here, it is so refreshing!
Blown away by how easy you make it all sound, and even though it isn't as easy as you make it sound you have explained everything to the nth degree so I can't see how anyone with even a tiny amount of electronics knowledge couldn't follow this video and make a great power supply AND know how everything works AND why you made the choices you made!
Blown away by it all basically! 😁👍
I will definitely be following your tutorial and making my own, with my own little changes as I know how and why I can and should do it!
Hungry for more now so I have subscribed and liked this, will be flitting through your other videos to see what catches my eye and my next few projects!
It is good practice to install a reverse diode across the regulator input to output pins, this prevents regulator damage when an external voltage is accidently applied to the output of the power supply, easily done with a bench supply.
How exactly can you do that?
Bill, Another Masterpiece !!!! !! ! I was both entertained and educated at the very same time. my brain learns a lot with the way you build these videos. I can only imagine the work behind this. But I will certainly be trying to at least see if I can locate a transformer :D thanks a ton !!
I am from Bangladesin. I am only a graphic designer. I had no practical knowledge of electronics. After watching your tutorial video I have made a Variable power supply. Salute you, sir
Bravo Bill. Excellent video and explanation. I watched the entire thing and was very happy that I did. Labeling panels has always been my weak point in building. You have given me some new ideas! Again bravo my friend.
Thank you for another excellent video Bill. It was really good. This is one of the best introductions to linear power supplies I've seen. I really like your benchtop supply you made as well. I just made the switching supply version using an ATx power supply a couple of months back. I'm tempted to try this for having a higher range and the variable voltage feature. Fantastic video!
Great project but couple of comments for anyone trying to build this exact design.
You will need a much larger heatsink for the regulator. A linear regulator drops the voltage between its input and output, the byproduct is heat. So if you have 1A load and the regulator input voltage is 30V but output is 5V, the regular will need to drop 25W of power (25V*1A). This is another reason linear regulator based power supplies are heavy. You can get better cooling using a thermal switch and controlling a fan when the heatsink gets too hot.
A lot of these LDO’s and older regulators (like classic the LM317) require enough bias current on the adjust pin to overcome the leakage current. The datasheet of the LM317 talks about this. You don’t need to use a trimpot to adjust the maximum output voltage, the datasheet will give you the equation and sometimes examples.
As few others have pointed out, a diode from the output to the input will help protect the regulator and discharge any capacitive loads that might at the output. LM317 datasheet has an example.
A nice addition would be a fuse at either the AC input or output of the rectified voltage. Putting a chassis mounted fuse at the AC input will help replacing the fuse a lot easier in case the fuse blows.
Lastly thank you for taking the proper precautions and insulating the AC main lines come into the box. A lot of other DIY projects don’t.
I'm Brazilian and despite not having a great knowledge of the English language I loved this class. I have no words to describe this wonder of knowledge and for sharing it with us. Thank you very much.
Success and a big hug from here Brazil
Luis, your written English is perfect. You hav a better grasp of the English language than do many for whom it is their mother tongue.
This was a really great video. Information is given clearly and knowledge above a basic level isn't assumed. You always seem to do a great job with putting chapters into your videos which makes it so easy to come back and refer to something or jump forwards to key moments.
Well done on the video, great guidance for anyone setting out. I am not new to power supply design but you have convinced me about the nibbler! Not a correction or a criticism but a good precaution for a build like this is to cover the chassis area under the circuit board with Kapton tape. A great instructional and anyone building the power supply should find it very useful for years to come.
Thank you for an interesting and informative video. Obviously there are time constraints on such a production, but I would recommend some brief additions which I think are important in an article which includes the word "designing" in its title:
1 - at about 19min, connect the rectifier to 48R//1000µF to show that on-load the output has a reduced voltage and some ripple, the lowest part of which must still be within the input voltage range of the regulator. Maybe add another 1000µF to halve the ripple.
2 - at or before 19min, add that the transformer must have a VA rating about 1.6 times (the raw DC output voltage) × (DC current output) or it will overheat.
3 - Stress that the peak input voltage to the regulator MUST NOT APPROACH its data sheet "abs max" spec.
I think these points could be covered inside a minute total, provided you don't take the extra time to explain why (2) and (3) are necessary.
Anyway, congratulations on a nice, instructive, helpful and practical article.
This is a great project, and it makes such a neat package :D
I'd love to see a project based on a programmable regulator and combined with an arduino to show voltage and current on a custom display. You could use push buttons to jump to a custom voltage, and a rotary encoder.
The front panel talk was an interesting segment, worthy of a video in and of itself, the various methods of creating a panel. Laser engraving, machine engraving, laser printer toner transfer (how some people make PCBs). Even using PCBs themselves as panels. One technique I've used it to print off the whole panel on paper, laminate it and cut it out, then glue that to the front panel.
Hi everyone what a good video 👍 . One of my hobbies is model railroading, and the amount of electronics used to make one work is amazing. Thank you Drone Bot Workshop 👍👍
As always, you provide clear an thorough information on the matter. Thank you for putting in the substantial effort!
I first got into electronics as a hobby when I was in college. The first thing that I ever built was a linear power supply that provided regulated 5VDC and regulated 12VDC using a 7805 and 7812.. Got most of the parts at the neighborhood Radio Shack. I designned and etched the board myself using a photo resist.
Thank you Bill for a great lesson in building and understanding a power supply. I also learned the difference between linier and switching. Thank you for sharing. Take care.
A friend of mine gave me 2 x HP 6214A linear supplies that didn't work. Took them home and fixed them.
That was like 20 years ago. They're still my lab power supplies!
14 volts at 1.2A is more than I've needed in all these years.
For big load testing, I have lead acid batteries used on my UPS and 60V 8A Boost converter with adjustable voltage and current.
Hello. Thanks so much for the input.
I need the power supply that can charge a 200amps battery. Something that gives over 14V 30amps
@@quickfixengineeringltd8035 What is the chemistry of your battery?
@@piconano dry cell lead
Not sure if you've been in hibernation or RUclips has been keeping you in the shadows but it's darn good to have u back!
And as luck has it, i was about to make myself a linear PSU with a 24v 4amp transformer I've had on the shelf for the last 2 years 😉.
Thank you sir 🙏 ❤️ greetings from India /UAE
I only wanted a linear PSU to build an audio streamer, I ended up here for over an hour. Great tutorial.
You have put a lot of effort into creating this very educational and organized video. I am very impressed!
Nicely done. For cutting larger holes in a metal or plastic chassis, I use a Dremel tool with a cut wheel. That works well and is quite quick. Safety glasses are a must. Take care 😊
What a great project and video! I watched the entire video and I plan to build one. Thank you so much for your great RUclips channel.
Thank you very much for the thorough presentation. I appreciate the efforts in making such a comprehensive lesson. All the best, Paul
Awesome! I can't wait to use this knowledge in a next project. Thanks for the christal clear explanation!
So I've been struggling to understand some concepts on how, why and where to use some electronic components. You just made them disappear. I've never seen a more well explained video in this field. Thank you so much, you have no idea how much I've learned from this video! 🙂
Super cool man. Thanks for the educational video!
Así fue justo como aprendí a lo largo de mi carrera de electrónica, la explicación es increíble y no queda lugar para dudas, excelente trabajo, el video es una joya llena de aprendizaje, enhorabuena y gracias por compartirlo!
Very good, simple and clear explanation of Linear Power Supplies.
You do an excellent job in how you move from general to specifics, and your production is great. Thanks for reminding me I used to be an electrical engineer in the late 1970s!
Very informative! I built my own linear power supply that I use to test dc motors. There's no voltage regulator, but it works great for testing stuff and to powering my homemade bandsaw 👍
Very valuable tutorial on the basics and fundamentals of building practical DC power supplies. There are dime a dozen of these on the web but you have done a very thorough job of breaking this down to a component by component explanation of why and how-to in the full circuit along with the design logic for both linear and switch-mode PS
Another great instructive tutorial! Thanks!
Excellent Bill ! Nice review of available linear voltage regulators. Regards, RJM
My English is bit poor but electronics project understand proper, this is good tutorial for all learners. Thanks and subscribed for you
Fantastic lesson!!! No words to describe how thankful I am! Cheers from Brazil!
This is the most informative and educational video around here. So much details and all explained with schematics and detailed testing and showcase about every single component, this is like school but 1000x better, you can learn a lot here. Thank you so much.
Thank you for taking the time to make this video, please keep up your great work.
This is an excellent tutorial demonstrating a practical and soundly designed power supply.
I apreciate the choise of the knobs for the potentiometer and the switch. they look nice
All of these videos you have made have helped me understand so much! Thank you!!
i really like the high level of your explanations.
great video, thanks !
You are a very good teacher ! Thanks so lot.
Great video, thank you very much for your sharing, greetings to you from Algeria🇩🇿💚.
Thank you again for sharing your knowledge; very well explained.
This is an excellent educational video ! My concepts are clearer now ! Thank you so much
Video is very descriptive, quite rare on YT. I knew most of info here, but I assembled knowledge from *tens* of other videos! And it was enough just to watch *this* video. :) I'm still sure despite all those "switching supplies", people MUST have linear PSU to power home projects - at least to exclude HF problems during development.
I'm in an epic 4 month deep rabbit hole right now you can't even fathom. Started with building a lifepo4 battery with a tutorial from Will Prowse. Months and hundreds of electrical related videos later, I find myself unable to learn enough about everything electrical.
Gonna be mfking Raiden by time I get my fill...
SMPS CAN BE more efficient than a linear voltage regulator - but not always. You have to examine the efficiency graph on the spec sheet and read the specs carefully. It is easy to be misled.
Linear VRs are much cleaner and more like a battery. SMPS can be noisy.
A SMPS may have trouble with inductive or high capacitance loads.
Many commercial SMPS do not have short-circuit protection.
Great project and thank you for sharing!
THIS Is the video I’ve been waiting for my whole life. So…so happy I found your channel.
Nice build, very informative.
Just found your channel and subscribed. Linear power supplies are also essential for music audio applications to power guitar amplifiers and effects where clean, noise free DC is required. For those who do not want to work with AC currents, you could consider making a video about constructing a power supply with +/-9 plus variable 1.5-12V outputs using a cheap wall wart as an input. This way you would not need the transformer or the rectifier either, bringing the cost, size and weight of the supply down considerably.
Thank you so much for making this video. I am confident I will be able to build one
Superb, as always! Thank you!
I think that’s really good advice, “if you’re nervous or scared about working with AC power, don’t.” Yeah, cause that really hurts if you hook it up wrong.
True master you are, I shall be your grasshopper.
Thanks for an excellent video! Actually thanks for another excellent video!!
You're simply marvelous! Yet another outstanding video!
An excellent explanation and an excellent presentation !
Thank You !
From Montreal, new to the channel and learning about electronics. Thanks for the tutorials!
Very nice build. I enjoyed this video from beginning to end. Thank you!
Your explanations are extremely well done ✔✔✔ easy to understand and clear to the point love your work. And the you for your time
Весьма подробно всё описано для новичков в электротехнике, но есть серьёзная оплошность - недопустимо малый размер радиатора на стабилизатор!!! Такой радиаторчик уместен, если блок питания использовать как демонстрационный, с минимальной нагрузкой!
Like the way every aspects are explained in detail
The explanation is so good. Excellent work. Thanks for the lesson.
Great project. Thank you.
Nicely done
Awesome video and channel!
There is one problem. When switching between fixed voltages, the voltage becomes momentarily unregulated. As the voltage spikes show at (1:09:00)
It seems like the voltage regulator just becomes a 0.7V drop diode when there is no resistor connecting it to ground. Any project connected to it might not like the full 22V rectified voltage.
Maybe it is better to have the lower part of the voltage divider fixed and put the switch and turn pot resistor on the higher part. Possibly with the 3.3V resistor as bypass resistor for the others, so that it is the minimum voltage. Or an other value bypass resistor to set a minimum voltage, so the regulator is not stressed out because it has no feedback from its output.
Ideally I would drop this ugly "voltage switcher" and just make output sockets with fixed voltage. It takes more space on device, but way easier and safer in terms of scheme (just use L7805 and like).
This is state of the art. Excellent work
Every time I watch your videos, your voice reminds me of Rob Stein of National Public Radio (NPR) science desk.
I missed this one I've not been well. Another useful power supply is what I need. Nice design 😁👍
Amazing class! The best one! Sorry about my english!
Great video, thank you!
Boom! mind blown...
I've been wanting a bench supply, I may give this a shot.
Loved your instructions! I have subscribed. By the way, I have already built my own power supply and added a reverse polarity switch plus two leds-green and red to indicate the polarities.
What a great experience is to newly listening from you. As always, clear and enjoyable. Thank you, indeed. Nevertheless, I am a bit confused about connecting the trimmer to control the voltage lie speed.
Hi, I am new to the channel. Wow, such great content. I feel like changing careers.
This is excellent, thank you!!!
You are a great teacher, thanks.
Very good video for building
One of the best tutorials I've ever seen, Thank U so much sir❤❤