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According to Pete


Here is the latest installment of "According to Pete" - our newest video segment starring SparkFun Director of Engineering Pete Dokter. This segment is designed to help answer some basic engineering questions as well as your questions that you submitted last time. We hope you find the video helpful! And just like last time, please feel free to leave questions for next time in the comments. We won't be able to answer them all, but we'll try to pick a few! Cheers!


Comments 72 comments

  • And here I thought my circuits worked with through the darkest magic conceivable, but now, I finally understand that the circuit is actually visited by an electric distributing easter bunny.
    But in all seriousness, this video was awesome and enlightening. Can’t wait for next months

  • Well, if we are picking out Pete’s mistakes, here’s a pet peeve of mine - a battery is not the same thing as a cell. A cell is a single anode and cathode in some sort of electrolyte. A battery is made up of 2 or more cells. AA, AAA, C, D, are all cells. A 9V a 6V (lantern) or a 12V (automotive) are batteries.
    The symbol for a cell is one short bar and one long bar (il) The symbol for a battery is repeating short-long-short-long bars (ilil or ililil). So in the schematic where Pete draws the arrangement of 4 1.5V cells in a row, the symbols are for 4 batteries, not 4 cells.
    Not that this matters one bit… :)
    Great video, though I too would rather have some more advanced topics…

    • Just to throw this out there, just in case anybody’s still reading this thread…
      If you’re going to spend your time picking apart my mistakes, I expect you’re going to have an uphill job. Not because I won’t make any, but because I expect to make LOTS. I don’t profess to be a genius, or even to be the most knowledgeable person on many of the topics I’m probably going to have to speak on. I’m very off-the-cuff and tend to simplify and generalize. I’m very rule-of-thumb oriented. I make lots of mistakes. And I expect that may irk some, but whatever. It’s all in good fun. I’m not likely to be put off by somebody saying that I “didn’t describe a closed system”. Nope, I sure didn’t. But I’ll get over it, I suppose.

  • I think we need a weekly “According to Pete,” very informative!

  • another noob series about electronics and stuff… I mean, if you look at all the content about electronics on the internet you gonna see that around 70% of it is for starters… you guys already have a tutorial about ohms law, there’s already a video from collin (the guy from makemagazine) and now this… I really tougth it would be something like 20 or 30 minutes answering a lot of question people made, but another stuff for beginners, really? :S
    I mean, when I was a beginner (I’m not a pro now, I’ll never think something like that) I liked this videos a lot, even If i see the same “content” over and over… but it’s enought… I mean, let’s move on more advanced stuff, like the “new products post” vids, they all(almost) show something cool about this new stuff sparkfun gets, and that’s amazing because there is nothing about them yet… this series should focus on that instead of what everyone already did:
    -ohms law
    -arduino blink leds
    -arduino serial communication
    -arduino analog inputs
    -etc
    I mean, there are the vid tutorials from jeremy blum and from collin cunningham on youtube already… do not do it again and again and… :S
    why don’t you guys go try to show some examples with products for people to know a lot more about what this products do before they actually buy them :S
    for example, could make a video showing the max weight the rover 5 can go with, how to make UAVs like the ones on the walls in this vids you guys make, etc… something usefull
    the noob can get used to electronics already, as most of the people here already did… now let’s try make people used to electronics to know more…

    • part2: I think pete is funny, and all that, but… yeah, noob things again?… please
      I’m not trying to look like a troll or something… I’m just trying to say what I first tought when I saw this… this a feedback, right? not a positive one but… yeah :S

      • No, I think you raise a valid point, and I know how you feel. But when presented with the list of questions, it was clear to see that people were coming to us that are pretty much noobs (not a bad thing, and I’m not calling anybody out). And I know there are lots of other sources for this information, but these people aren’t going there, they’re coming here. And they’re either not getting their questions answered by our own existing tutorials or they haven’t seen them yet. So do I try to help them out, or do I blow them off?
        I like helping new people. It’s fun, and they’re generally really enthusiastic about the material. But no, I don’t intend on this being all beginner stuff. But if I’m going to address the beginner questions, I should probably do it at the beginning. Once we get that stuff out of the way and we get rolling, I expect much more involved posts.
        I sweated over this, I really did. I was afraid I’d see 40 posts like yours, and was amazed that I didn’t. But I hear you.

  • “What do you do when you have a full tank of gas? Step on the accelerometer!” 2:50
    Why would you do that!? :-D Vocal equivalent of a typo? :-P

    • I noticed that too…
      I try to avoid stepping on my accelerometers. It tends to crack the solderjoints.

      • Yeah. When I watched it the first time, I was like “ah, cr@p, you idiot”. One day I’ll do a video of nothing but wrong words.

        • Don’t worry about it too much. We know what you meant :)
          But it might be a good excuse to build an Arduino Based Teleprompter!

  • Once a month!!!! I can’t believe!!! Please, make it once a week!
    Thanks,
    Fabius

    • +1! I would love to see these vids more than once a month!! :-)
      Altough I would like to see some more advanced topics as well ;)

  • I always though it was V=IR

    • I learned V=IR as well, I also learned that V was often E etc so I would be able to recognize what people were talking about if they used it. I don’t remember any of my professors (or even text books) using E consistently though.

      • I do, but it was only the old instructors. (Sorry Pete!)
        This gave rise to some other mnemonics for remembering Ohm’s law, such as PIE –> P = IE, where I just learned it as P = IV. Not nearly as tasty…
        Apparently EMF and Voltage are technically not the same, even though in practice the terms are used interchangeably. Here’s some light reading on the subject:
        http://en.wikipedia.org/wiki/Electromotive_force#Electromotive_force_and_voltage_difference
        Great videos, Pete! Thanks for taking the time to put these together.

      • V=IR where V is Voltage, however voltage is either emf (hence the E) or potential difference. It’s something to do with the battery terminals.

    • Hmm, I was taught that it’s U=IR and P=UI….
      Gotta love all the different conventions.

    • I learned ohms law before I could read or write, so I always remember “The voltage equals the current times the resistance”

  • I teach principles of electricity at a local museum, so I’m always eager to see how other people do it. Thanks!

  • Great post Pete! Newbie hackers the world over thank you.

  • As someone who studied circuits in college, at this rate, you’ll be doing 100 level electronics for the next 3 years, in my opinion.
    I’d like to see more advanced topics, is all I’m saying. I understand the need to teach the basics, but there are hundreds if not millions of resources(assuming people still can read books) for the basics. Advanced topics are much more rare.

    • Yes - the beginning stuff is good too - I’m a beginner, and I’m still learning some of it, but maybe split the video into two parts, possibly related - beginners can see the first part, then maybe understand the next, and advanced users could see the first as a bit of review before seeing the more advanced second part.

  • It might be basic material, but aside from the small writing, it was done very well. I dont see anything wrong with starting with the basics, it certainly cant be bad for expanding your business. Maybe twice a month, one on basic questions, one on more advanced topics?

  • Oh man! Loop analysis next! XD

  • In the book Make: Electronics (page 26) the author says that the letter I is used because current originally was measured by its inductance.
    As a beginner this video helped my understanding a little bit more. Thanks for the explanations.

  • Hi Pete!
    Could you please write on a blackboard with a little bigger font, to make it easier to look onto the formules
    Thanks a lot!

  • E for voltage comes from electro magnetics, specifically Maxwell’s Equations.

  • Why are you calling the capacity of the battery current rating?
    I have always considered the current rating the maximum current a battery/power supply/ect can supply. I consider the mAh rating the capacity of a battery.

    • IT’S ETC. NOT ECT.!!!

    • That’s how I see it, too. There are a lot of ways to specify a current rating (peak, maximum sustained, etc.), but that’s a quibble.

      • Yep, you guys are right. I blame myself; I was a deer in the headlights of that damned camera.
        Current rating is usually represented by a “C” rating, where C represents the capacity of the battery. For example, the current rating on my metal hydride that I showed is probably something like 30C, which means it can dump 30 times it’s capacity continuously. It might have a burst rating of 40C (not that it blows up, but it can deliver 40C in short bursts).

        • In MAKE I learned that Coulombs are gallons and Amps are gallons per second, so shouldn’t the capacity of the battery be rated in Coulombs?

  • Let’s not short (no pun intended) Mr. Ampere or Mr. Volta.
    Alas, I in ohm’s law cannot be attributed to a historical wizard but only the notion of Intensity.

  • Exactly. It sure sounds weird when you page him too.

  • Best post ever!!! Thanks a million.

  • aha I love the speaker

  • I have a suggestion for Sparkfun. Since you apparently have a contingent of neophytes in your customer base, why not carry some of Forrest Mims' books? They are an excellent resource for beginners, and can be pretty handy at times for a quick and dirty reference for old timers.
    Just in case Sparkfun decides these books don’t fit into what they want to carry, interested people can go to Amazon and search on the author’s name. They even have a page dedicated to him at: www.amazon.com/Forrest-M.-Mims-III/e/B003UGHJVE/ref=ntt_athr_dp_pel_pop_1

    • What do you mean Forrest is for just neophytes? I know Engineers that have his dog eared Green book and falling apart Yellow book from Radio Shack on their desk, at work! More than once have I gone to the Forrest Mim’s Bible to get inspiration, and get re-educated. I know everyone here just love to delve into a 64-bit Karnaugh Map (K-MAP) and has built up their excel spread sheet so it spits all 64 answers (or more) out.
      I have lost count of how many times have I found Mr. Mims’ Engineer’s Note Book has brought me into awareness. Just this week, I was sure I was looking at a RS latch when it turned out to be a D Flip-Flop. I know, just one misplaced NAND gate inverter.
      Yes, you could go to college and sit through a logic class and learn that you can make a RS flip-flop from one NAND gate and one NOR gate. But where’s the Sparkfun sense of joy of letting out all the Blue Smoke with that? And YES it was fun watching all these college seniors put a NAND gate RS flip-flop together and freak out over the chase state (because they did not know how to read their truth table). Ok. That was fun. But for a lot of people, we would have never got our hands wet in logic if it wasn’t for Mr. Mims. (Before all those people in the crystal palace of learning telling us we didn’t know what we were doing, and there for shouldn’t be do it.) I know people that still consult the LED table of wavelength to decide their forward voltage for the equation Rs= (Supply V-LED Voltage)/(LED Current).
      I guess what I am saying is His books are not just for someone new to electronics. If I ever get grandchildren, I know his books will be one of the first things I will buy them. It’s the best gift a grandparent could buy for their grand kid (along with four full size bread boards and parts for their first 120VAC to 12V DC power supply, four 75HC193s, two 555 timer, a dozen of 74HC00, 74CH10, five 74HC154s, odd and ends of resisters and Caps and LEDs, a four quarts of ferric chloride, ten 12 by 14 inch copper cladded fiberglass boards and a Sparkfun soldering iron, and a good drill press, along with some #32 drill bits, and access to the laser printer).

    • I agree, Mims' books got me into electronics!

    • I’ll third this suggestion. I have some Mimms books on my shelf that are going to my kids as soon as they’re old enough to understand them.

    • I can only support this suggestion! I started reading these books when I was 16, and it was so clear and well explained, I could experiment and learn electronics by myself afterwards. 8 years later and I got a master of science in electronics :-)

    • Thanks for the link! These look fantastic!

  • Awesome video! Looking forward to next month’s

  • Unrelated, but Pete, is your dad or uncle a surgeon?

  • I’m slightly embarrassed to admit how incredibly helpful that was for an electronics noob like myself. Great video - can’t wait for next month!!

  • Who’s your Camera man? William Shatner? The camera keeps jumping from place to place! Heh.
    I always liked the “Water through pipes” analogy for explaining electricity.

    • The water through pipes explanation of electricity is why the Hydraulic Fitters at my work quite regularly show up the electricians when it comes to diagnosing problems…
      Quite frankly though, Hydraulics scare me!

  • E for voltage comes from “Electrical Force”(If I remember right) and I is for amps or and comes from the French word “intensité de courant” which means Current intensity.

    • Ah, beautiful! One of those things I used to know. That list gets longer every day.

      • We Europeans use U and looking at the english Ohm’s law page, one of you english speaking countries use V :) Ahhh always fun when there is a standard

        • We use V for voltage and I for current in the UK (or at least as far as A level (exams at age 18) we do).

        • Wait, so if everyone is using a different variable… Why can’t we just use anything? For example a V!

          • Truth is, you can. the rules here are
            1) Be consistent, so you know what you are saying.
            2) Clearly define which symbol is being used for each variable, so others know what you are saying.
            Using the convention of those around you is merely an extension of rule 2.

    • It’s just one of those old nitpicking things they used to do. Technically a battery produces an electromotive force while a resistor produces a voltage drop. I was told that they used to be treated separately to make mesh analysis more intuitive. Who knows maby someday we will stop treating resistance as if it’s separate from impedance and have V=IZ.

    • I learned that E stood for “electromotive force”. I never did know where “i” came from, so thanks for that. This means I can blame the French for having to use “j” for imaginary numbers! ;-)

  • once a month.

  • Really?? Is that little guy flipping us off??

  • Is this going to be every Monday? I look forward to adding this to my schedule.

    • Once a month. Will it be on the first Monday of every month? I have no idea.

      • I second it should be MORE THEN ONCE A Month.
        Besides it would give Pete-O a chance to get all the bugs worked out… including the pants of the guy holding the camera OR are we going for the History Channel’s UFO series make the viewer’s sea sick?

      • First Monday of every month. I wouldn’t want to see my face up here every Monday.


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