Abstracting transistors into high-level design

Although it’s not the best way of understanding computers, most people tend to imagine electronic devices as black boxes filled with magic and blue smoke. Even microcontrollers, the most fundamental means of computation, are treated like little black plastic centipedes with metal legs. In a series of blog posts, [Andrew Gibiansky] is tearing down the walls of obfuscation and illuminating the world of transistors, gates, and FPGAs.

The first blog post goes over the idea of electronic circuits as a waterfall; a positive voltage is a reservoir on a mountain top and ground is sea level. This idea is extended to the lowly transistor acting as an electronic switch, able to turn a circuit on and off.

Continuing on to logic gates, [Andrew] covers the NOT, AND, and OR gates before moving on the flip-flops and SRAM. These can, of course, be modeled in Verilog and VHDL – programming languages that abstract the world of transistors and gates into a much more human-readable form.

[Andrew] is far from done with his series of blog posts, but judging from his work so far it seems to be a great resource for untangling the obtuse concepts of gates and memory into the coherent design of a computer.

ATtiny Hacks: ATtiny-controlled 4x4x4 LED cube has a unique design

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[Tom] recently started experimenting with Charlieplexing, and wrote in to share the 4x4x4 cube he built with an ATtiny24. Similar to this minimalist 4x4x4 LED cube we featured the other day, [Tom’s] version attempts to use the least pins possible to drive the LEDs, but in a different manner.

[Tom] didn’t want to sacrifice brightness, so he decided that the LEDs would have a 1/8 duty cycle. The problem is that the ATtiny’s I/O ports can’t support that kind of current so he needed a different means of driving the LEDs. Rather than employ any sort of shift register to control the LEDs, he opted to exclusively use transistors as he had done in previous projects.

For his Charlieplexed cube to use a total of 9 I/O pins he had to get creative with his design. He broke each level of the structure into two non-connected groups of LEDs, utilizing diagonal interconnects to get everything wired up properly.

It seems to work quite nicely as you can see in the video below. While it uses two more I/O lines than the other ATtiny cube we featured recently, we love the simple, shift register-less design.

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DIY guitar fuzz pedal

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Instructables user and Community Manager [Randy Sarafan] recently put together a tutorial on how to build an ages-old musical standard, the “Fuzz Pedal”. He says that the secret to rocking out is fuzz, so if you can handle both a soldering iron and a guitar, this project is for you.

When you take a close look, the pedal’s components are actually quite simple. The distortion is created by a pair of transistors, which in his case are vanilla NPNs from RadioShack. We have covered other distortion pedal builds before, and they have used germanium transistors to obtain a ‘creamier’ sound – you should be able to swap these cheap ones for uprated models with little trouble.

The handful of components were soldered neatly to a piece of perf board, and placed into a sturdy metal case that looks like it can withstand even the harshest abuse. He’s got schematics and a BOM in his writeup, so all that’s keeping you from a rocking weekend is a little bit of time and a soldering iron – what are you waiting for?

Stick around to see a quick video of [Randy’s] fuzz pedal being built.

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Intermediate Concepts: Building discrete transistor gates

[Simon Inns] has put together a lesson in digital logic which shows you how to build your own gates using transistors. The image above is a full-adder that he fabricated, then combined with other full adders to create a 4-bit computer.

Don’t know what a full adder is? That’s exactly what his article is for, and will teach you about binary math and how it is calculated with hardware. There’s probably at least a week’s worth of studying in that one page which has been further distilled into the five-minute video after the break. Although building this hardware yourself is a wonderful way to learn, there’s a lot of room for error. You might consider building these circuits in a simulator program like Atanua, where you can work with logic gate symbols, using virtual buttons and LEDs as the outputs. Once you know what you’re doing with the simulator you’ll have much more confidence to start a physical build like the one [Simon] concocted.

Finding this project a little too advanced? Check out our Beginner Concepts articles to help get you up to speed.

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