According to Pete #42 - Resonance Circuits

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So you've always wanted to learn about resonance circuits, but didn't know where to start? Well, if we had a nickel for every burgeoning engineer or electronic enthusiast with the same conundrum, why, we'd have several handfuls of nickels.

Fortunately for you (and for the world, really), there is Pete Dokter -- the SparkFun Director of Engineer, goatee-enthusiast, and all-around swell fella -- who is here with an episode of "According to Pete" on just that topic. Forget turkey, let's talk resonance circuits.

Yes, Pete said "It's March" in the video. Listen, we filmed this at the end of March but have been swamped with all the things. Better late than never, right?

As always, if you have any questions about resonance circuits, Pete's favorite food, the meaning of life, or anything else that's on your mind, we welcome them in the comments below and we'll do our best to get 'em answered.

And there you have it, According to Pete.*



*Signoff under construction.


Comments 15 comments

  • 8:01, I said "underdamped". I meant over. Overdamped yields a slow rise. Sorry about that...

  • Any chance According to Pete #32 can be made public again? It's the only one I haven't been able to watch.

  • Critically damped low pass car suspension? Reminds me of my first job after getting my engineering degree (in 1980). There was a railroad track near the office, that was elevated maybe 10 feet above the rest of the terrain, so you had to climb up the small hill, cross the track, then proceed down the other side. I discovered that if I hit it at just the right speed in my pickup, I would actually go through zero G at the top, missing the bumps caused by the railroad. (The wrenches under the seat would drift up a bit at the zero G point, and then clatter as I went back to having apparent weight. At least one co-worker refused to ride with me to get lunch, because he couldn't get used to zero G in a pickup truck. I always thought it was a lot smoother ride than getting tossed around by the tracks.

    BTW, I still think, Pete, you should do an episode on how the acoustics problems for the "new product Friday" episodes were solved!

  • So I made one of these following the same schematic shown on the white board. It has the signal out in a weird spot. I was not able to see a signal there, just the input dc voltage, which makes sense as there is a direct path through the inductor to that "output" and the inductor acts as a dc short circuit. However, when I probed the emitter of the transistor I saw the expected signal.

    This diagram is consistent with other ones I've seen and even the one on the wikipedia page for Colpitts Oscillators. How could you not get a DC short circuit with that setup? I must be missing something.

  • Thanks Pete, This video would be an excellent segue to Frequency mixers. Maybe build a Bat Detector?

  • Pete, I am curious as to what we are hearing on the radio (what is the source of the audio)? Your ears can't hear anywhere close to 650kHz and the scope is showing a pretty nice sinusoid (maybe there is some AM going on, but its hard to tell from the few waveforms shown. I have almost no radio experience so terms like short wave, continuous wave kinda go slightly over my head (but I have messed around with a Colpitts to broadcast, over a distance of about 3 feet, the signal of a electret mic (a.k.a a really useless bug)).

  • Thank you Pete was was fun to watch!

  • That was GREAT!!!!, more please

  • Great explanation of impedance and reactance! I wish my EE prof from almost 40 years ago was as entertaining and would've explained it as well as you. If he did, I might not have changed majors and might have stayed in EE. Even though it's not new material for me, I did learn something and have a better understanding of it now. Thank you!

  • What's your favorite food? Also, I love according to Pete. As someone who has no high school electronic class, it helps me learn about stuff that I would never figure out otherwise.

  • What scope and bench supply are you using there ?

    • Scope: https://www.sparkfun.com/products/11766

      PS: a very old one that we haven't sold for a long time.

  • Nice! I would like a follow up that is more application using these types of circuits.

  • If you modulated the base of the transistor, say, with a microphone or an MP3 shield, could you pick up the modulation on your radio?

    • Not only that but as Pete demonstrated; if you put a metal diaphragm next to the inductor and yelled at it you would have a FM transmitter. Great video Pete!

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