According to Pete - Voltage Regulators


For the novice electronics enthusiast, powering your project properly can be one of the most difficult pitfalls of DIY embedded systems. In today’s edition of “According to Pete,” SparkFun Director of Engineering Pete Dokter helps you out by diving head-first into the world of voltage regulators - why you want them, how to use them, and which kinds you want.

Vimeo version can be found here

Please leave any questions or suggestions in the comments section below. . We hope this video help explain how to incorporate a voltage regulator in your next project!


Comments 52 comments

  • OK, in the later bit of the video, the discharge path that I can’t easily see is through the base-collector junction on the power transistor. I really should have known that at the time, but it occurred to me later that night accompanied by “stupid, Pete”.

  • Great tutorial

    I hope you’ll also cover step-down (buck) converters like the Traco Power TSR 1-2450 (5V @1A) and TSR 1-2433 (3.3V @ 1A). They are switched drop in replacements for 78xx regulators. (It would also be nice if Sparkfun.com carried them. Hint, Hint.) There’s also the MC34063 that you guys do carry.

  • Nice tutorial ! Looking forward to one on switch mode regulators or whatever they are called…

  • Have two requests: spectrum analyzer and vu meter. Possibly for´╗┐ your workspace amp?

    Kitchen Cabinet

  • Pete , You are a pretty young fella . How come you show power flow from Pos to Neg? Bout time we all got real . It goes from Neg to Pos and should be shown as such by the “teachers”. Thanks

    • Young fella at 45? I like that. But I’m with you. I learned electron flow first, then was warned that others prefer conventional. Most others, in fact. I got tired of having people look at me funny when I showed current running from negative to positive. Now I’m pretty forgiving about how somebody presents current flow, as long as they really understand what’s going on.

  • Hi Pete, I wonder if it is possible to get a write-up of what you were saying in the video? I’m deaf, and unfortunately Google’s captioning software doesn’t work very well as you probably know. I don’t feel great about putting you to more work, but on the other hand, I think what you have to say is well worth paying attention to. If you don’t have the time to do a translation maybe you can point me at some study resource that textually says essentially what you did in the video. Thanks!

    • It’s too bad transcriptions aren’t enabled to be a community effort.. or is that an option? If it’s possible for anyone to go to a youtube vid and submit a version of the text I’d gladly do it for all the “According to Pete” vids. Do you know if that is a possibility?

      • At a glance, it doesn’t look like YouTube offers a good mechanism for community members to do this. I can imagine it being sort of a moderation nightmare if they did. But maybe we could come up with something where we have a page for a video with an editable transcript.

        I’m not promising to do this today, mind, but I don’t think it’d be that difficult…

        I wonder if a GitHub transcription project would be too much of a barrier to entry for volunteers?

        • UniversalSubtitles (http://www.universalsubtitles.org) does a good job with community editing of captions.

          Guidelines for captioning are here: http://www.dcmp.org/captioningkey/

        • GitHub.. No thang.. I’ll for sure add to it if you guys wanted to set it up that way. Sparkfun rocks! My user there is doddy1985 but just post the link to repo here I guess whenever you have a chance to set it up. I’ll request to contribute after that and chip away at it.

          I’m not sure what would be the best way to format: (Time and text then newline perhaps?). Anyways, I’ll wait to hear back.

          edit1: Looks like your link has a format under the Caption File tab; Begin time, End Time (\n) Text (\n\n)… So I can probably start hacking something together tonight and commit later.

          • Thank you very much for whatever you can do. You may want to see my additional post above, saying I will be happy with whatever can be done here. I really do appreciate it. I will keep my eye on this thread and watch for any comments. Again, let me express my gratitude for your thinking so proactively about my access to this content, no matter what happens here.

            • hey, only got about half way through the vid tonight.. it’s pretty impressive how many words can be spoken in one second on average.. I don’t think it’s something I ever paid attention to before haha. Anyways, ya I’ll knock it off soon. No probs :)

              • I put up a bare repo for trying this out. There are probably all sorts of ways to go about it, but maybe just a “captions” directory with files by name of episode or something?

                Pull requests welcome from any and all interested parties.

                (Edit: Or we can probably define a team of transcribers with access to that repo, but pull requests are a nice model for letting the general public contribute. Let me know your thoughts.)

                • After reading Doddy’s latest post, I want to help also. I updated to the very latest git version on my local machine, then I started studying the fork-and-pull model described in the Github Help area. I logged in to Github (my username is BobCochran) and forked the sparkfun/according-to-pete repo to my account, then I cloned that to my local. Then I added the sparkfun/according-to-pete as the upstream remote. So I too should be able to help with this in whatever way I can and submit pull requests now. Does anyone have an idea of how I can help? I was wondering if I can take Doddy’s work and create an HTML version of it. Or perhaps you have other ideas? If I can serve in some way let me know. Oh, feel free to add me as a Github collaborator, too, if you want.

                  • See here.

                    Does anyone have an idea of how I can help?

                    I’m not sure offhand, but I’ll bet something will emerge. Maybe adding some kind of guideline writeup on what’s helpful for deaf users and what’s not, or some notes on captioning/transcription formats?

                • Hey I’ve also cloned and committed to my local. When you have a chance could you add me to collaborators for this repo? I think it’s just under settings->collaborators. I don’t think I can do a pull request without already being a collaborator. My user is: doddy1985.

                  Cheers!

                  • In the interests of getting things going, you and BobCochran are now both collaborators on this repository.

                    You can actually do a pull request from a forked copy of the repo back to ours - that’s sort of the intended overall model for GitHub, and I think it might work better in the long run, but let’s see what happens the way things are.

                    • Thank you, Brennen! I’ll try to float my own contributions for you and Doddy to look at. I spent some of Saturday and nearly all of Sunday studying git and forking the Sparkfun repo, then playing with a clone of my fork on my local machine, then pushing some html content to my remote fork. I will use pull requests to get the content to you and Doddy.

                    • Hey my bad. Maybe you were right about the Github thing being too big a barrier for us common folk :).. I’ll keep that in mind for the future though and just use my forked repo to work from and stage that way. Anyways, THIS episode captions are up on the remote repo now. There may be some need for modifications so I can certainly work on anything that is either buggy or too verbose for a time frame.

                      • Doddy, wow! I just skimmed the first couple pages of the SBV file and it is pure gold! Thank you, thank you, thank you for doing this for me! And also for other deaf individuals who have the interest. Thank you so much! I’ll give this a close reading over the next couple of days. Perhaps I can take this and turn it into an html document as well. At this point I’ve fetched from the Sparkfun repo, which I call “upstream”, and merged it into my local repo. Then I pushed my local repo to my personal remote. I’ll let you know when I have content that is good enough to put on the upstream.

                        • I’m glad to help. My wife is hard of hearing so I have some understanding of how difficult it can be when viewing media without captions. I personally prefer captions as for whatever reason it helps me remember material better when I read it rather than just hear it. Anyways, I’ll eventually get through the other ‘According to Pete’ episodes but it may take a while. I figure it’s about 3 hours of transcription to every 30 min video or so.

                          Cheers!

                          • Doddy, I added some content and did a pull request last night from my remote (which forks the repo that you pushed to). Brennen merged in my content. I am working towards taking your captions file and crafting a web page from it. You might want to do a ‘git fetch’ to get the content I added. I welcome comments from you and Brennen via email.

                      • This is great to me also! Thank you so much! I really appreciate your work in this. I got confused about following the conversation thread. I’ll pull down your captions and enjoy them! I think what I need to do is ‘git fetch upstream’ and then merge them into my local repo. I’m hoping to turn some of your work into html documents. When I’m ready I can push them to my personal remote repo and from there do a pull request. I’m pretty new to git.

                      • Anyways, THIS episode captions are up on the remote repo now. There may be some need for modifications so I can certainly work on anything that is either buggy or too verbose for a time frame.

                        This is great. I’ll see what I can do about getting it added to the YouTube vid.

                • I just cloned the repo. I’ll wait for more content to show up. This might offer Pete some interesting possibilities as well.

                • Believe me, I am most grateful to you, Doddy, Pete-O and all the others involved. I agree that GitHub is a good idea. I’ll keep an eye on the repo and in addition to making use of the content, see if I can help out in some way. This is timely: I suspect I may have fried my brand new Big Easy Driver last night with my bench power supply. We will see. Maybe the device is so well built it shrugs off mistakes by the user. To get portable operation from it I’ll need to resort to batteries, and that inevitably means voltage regulators.

    • I… wow, that would be a lot of work. Let me check with some people and see what the options are for you (or me)…

      • I know we’ve talked about this problem in the past, and I think the folks in Marcomm might have experimented with paying people to do captions, but it turned out to be a pretty big time / money sink.

        It’d be cool to figure out a good general solution. Maybe we could find a decent way to crowdsource transcriptions.

        • Hi! @doddy as well, I want to thank all of you for looking into this. Whatever you can do, I’ll be satisfied with. I did watch Pete-O’s entire presentation and I immediately realized 2 things: first that I need to know his presentation textually, and secondly I could see from his whiteboard drawings that it is a topic that I need further training in. That led me to ask for some sort of a transcript or caption. I wonder if the National Captioning Institute can be a help here? http://www.ncicap.org/

          I am willing to work with you folks proactively in any way I can regarding this. I can wait; this does not need to be done today or this week or next; I can be patient. I guess I am so completely impressed with the efforts being made to offer some training by video, that I too would like access to the voice content. Thank you very much for whatever you can do. I understand about time and budget constraints.

  • I find that using a >16W base resistor is poor design. If you want your circuit to survive an output short condition, add protection circuitry to deal with that. Two transistors, three resistors and a capacitor would do the job, and probably be cheaper than using a high wattage resistor. You also totally neglected to account for base current in your series transistor. A high voltage, high power transistor will have a current gain well below 100, that’s more than 2mA in your application. A current gain of 40 would result in 5.5mA base current, again resulting in a base resistor value of 4.76kohm.

    • You seem angry… “Poor design”? Come on, now. I can think of at least a half a dozen ways it could be accomplished, and a single component is the simplest. “Probably” cheaper? It had better be significantly cheaper to justify the extra work (designing, spec'ing parts, purchasing, building and testing the extra circuitry). Being clever at the expense of simplicity does nothing for me.

      Neglected the base current? Sure did. Hey, man, the video was a freaking half an hour. I gotta draw the line somewhere. But yes, the final design will account for everything you mention. Worth mentioning, though, the circuit has a great ability to balance itself and function none-the-less. But I also accept that all designs are iterative. I may have to go back and change something. Meh.

  • Wow, this really opened my eyes to how electricity works. I was always wondering how the heck to account for current drawn into an IC but I guess so long as the voltage expected by IC is regulated (say a 5V clean supply) the IC’s load will draw the appropriate amount of current under ideal temperature/other conditions?

    I guess I always thought to tackle the two issues separately, that is, design for supply voltage, and also design for supply current with say a constant current source. But I guess if one is properly designed, the other follows suit? I hope I followed along correctly :)

    • Effectively, yes, the IC will take the current it needs and no more. As for current taking care of itself if you design the regulator right… sort of. You have to have some idea of how much current you’re going to need in the first place, then make sure your regulator can source it while not cooking itself.

      • That makes sense.. So if the IC would potentially draw 1A (which is maybe outrageous for most cases but just as an example for now) and the supply only has an output of 500mA DC then you need to up the wattage for source to support at least say 1.1A @ voltage.

        As for the ‘cooking itself’ issue, does that mean to spec out parts to handle a higher wattage than what is expected to go through (as you mention that doubling factor in the vid)? What about the extra current (.1A from example above), does that just feed back to ground?

        • Well, if you need more current, you need the part in question to say it can deliver at least what’s required. Just because a regulator can dissipate more power doesn’t guaranty that it’ll source as much current as you need.

          To pick a regulator, in general, you need to know what the required regulated voltage is, how much current you’re likely to need (average and peak), and what your supply voltage is. Start with parts that satisfy those requirements, then weed them out based on power requirements. The trick is that a given 5V regulator might be rated for 5V out @1A with a max input of 35V, but it might not be rated for 30W (though a TO-220 package might handle it with a big heat sink). And data sheets won’t just give you a power rating, because they assume that you’re already going to heat sink it, so they give you a bunch of graphs depicting performance based on all of the factors mentioned above.

  • Great discussion Pete. Enjoyed. What do you think of running directly off of battery on uber-low-current designs, like MSP430 or even less. I’m aware about the ratiometric stuff (sensor output depends on supply voltage) but do I need a Vreg for low current apps where the supply can gently wander?

    • As long as you’re aware of the operational parameters, you can design for them. If you’re just doing a one-off function where it’ll be complete before the battery dies, you probably don’t have to worry much. But if it’s something that’s going to remain operational over the life of the battery, you may need to characterize that full cycle so you can repeatably predict the circuit’s behavior. Does that make sense?

  • Please make a “BALLAM!!” Pin!!!! how would you even spell that??

    Blam…BALLAM

  • Thanks Pete! That high voltage regulator will come in handy. With the guitars you work on and the high voltage, is it safe to assume you’re working on a tube amplifier? If so, did you pick out a pre-existing design or cook something up yourself? I got 3 of those beast’s under my belt so far.

    • OK, you got me. It’s for a tube amp. The regulator’s not my design, just a variation on a theme you can find around the web. Google “LM317 high voltage” and you can see lots of ways to get what you need.


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