Category Archives: oscillator

A Vintage Single Transistor LED Blinker

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[Eric Wasatonic] had a box of SWB2433 transistors that he had very little information about. In order to discover their properties, he fired up his curve tracer to compare these transistors with more common ones. He noticed the SWB2433 exhibited negative resistance while the similar curves of a 2n3904 didn’t. Then he reverse-biased the two transistors: the negative resistance region on the 2n3904 was less than that of the SWB2433, but it was there, and a 2n2222 had a bigger region. Using this knowledge, he developed a relaxation oscillator circuit which uses a negatively biased transistor.

Using one transistor, one …read more

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Soft Robot With Microfluidic Logic Circuit

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Perhaps our future overlords won’t be made up of electrical circuits after all but will instead be soft-bodied like ourselves. However, their design will have its origins in electrical analogues, as with the Octobot.

The Octobot is the brainchild a team of Harvard University researchers who recently published an article about it in Nature. Its body is modeled on the octopus and is composed of all soft body parts that were made using a combination of 3D printing, molding and soft lithography. Two sets of arms on either side of the Octobot move, taking turns under the control of a …read more

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Russian Decapping Madness

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It all started off innocently enough. [mretro] was curious about what was inside a sealed metal box, took a hacksaw to it and posted photographs up on the Interwebs. Over one hundred forum pages and several years later, the thread called (at least in Google Translate) “dissecting room” continues to amaze.

If you like die shots, decaps, or teardowns of oddball Russian parts, this is like drinking from a firehose. You can of course translate the website, but it’s more fun to open it up in Russian and have a guess at what everything is before peeking. (Hint: don’t look …read more

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Atmel Removes Full-Swing Crystal Oscillator

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It is one of our favorite chips, and the brains behind the Arduino UNO and its clones, and it’s getting a tweak (PDF). The ATmega328 and other megaX8-series chips have undergone a subtle design change that probably won’t affect you, but will cause hours of debugging headaches if it does. So here’s your heads-up. The full-swing oscillator driver circuitry is being removed. As always, there’s good news and bad news.

The older ATmega chips had two different crystal drivers, a low-power one that worked for lower speeds, and higher-current version that would make even recalcitrant crystals with fat loading capacitors …read more

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Improving the RTL-SDR

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The RTL-SDR dongle is a real workhorse for radio hacking. However, the 28.8 MHz oscillator onboard isn’t as stable as you might wish. It is fine for a lot of applications and, considering the price, you shouldn’t complain. However, there are some cases where you need a more stable reference frequency.

[Craig] wanted a stable solution and immediately thought of a TCXO (Temperature Compensated “Xtal” Oscillator). The problem is, finding these at 28.8 MHz is difficult and, if you can find them, they are relatively expensive. He decided to make an alternate oscillator using an easier-to-find 19.2 MHz crystal.

How …read more

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Oscillator Design by Simulation

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[Craig] wanted to build a 19.2 MHz crystal oscillator. He knew he wanted a Pierce oscillator, but he also knew that getting a good design is often a matter of trial and error. He used a 30-day trial of a professional simulation package, Genesys from Keysight, to look at the oscillator’s performance without having to build anything. He not only did a nice write up about his experience, but he also did a great video walkthrough (see below).

The tool generates a sample schematic, although [Craig] deleted it and put his own design into the simulator. By running simulations, he …read more

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