Direct Digital Synthesis (DDS) Explained By [Bil Herd]

November 24, 2014 by Bil Herd 42 Comments

One of the acronyms you may hear thrown around is DDS which stands for Direct Digital Synthesis. DDS can be as simple as taking a digital value — a collection of ones and zeroes — and processing it through a Digital to Analog Converter (DAC) circuit. For example, if the digital source is the output of a counter that counts up to a maximum value and resets then the output of the DAC would be a ramp (analog signal) that increases in voltage until it resets back to its starting voltage.

This concept can be very useful for creating signals for use in a project or as a poor-man’s version of a signal or function generator. With this in mind I set out here to demonstrate some basic waveforms using programmable logic for flexibility, and a small collection of resistors to act as a cheap DAC. In the end I will also demonstrate an off-the-shelf and inexpensive DDS chip that can be used with any of the popular micro-controller boards available that support SPI serial communication.

All of the topics covered in the video are also discussed further after the break.

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Bil Herd: Computing With Analog

July 25, 2014 by Bil Herd 34 Comments

When I was young the first “computer” I ever owned was an analog computer built from a kit. It had a sloped plastic case which had three knobs with large numerical scales around them and a small center-null meter. To operate it I would dial in two numbers as indicated by the scales and then adjust the “answer” by rotating the third dial until the little meter centered. Underneath there was a small handful of components wired on a terminal strip including two or three transistors.

In thinking back about that relic from the early 1970’s there was a moment when I assumed they may have been using the transistors as logarithmic amplifiers meaning that it was able to multiply electronically. After a few minutes of thought I came to the conclusion that it was probably much simpler and was most likely a Wheatstone Bridge. That doesn’t mean it couldn’t multiply, it was probably the printed scales that were logarithmic, much like a slide rule.

Science Fair Analog Computer

Old meets new: Analog and digital computation

Did someone just ask what a slide rule was? Let me explain further for anyone under 50. If you watch the video footage or movies about the Apollo Space Program you won’t see any anyone carrying a hand calculator, they didn’t exist yet. Yet the navigation guys in the first row of Mission Control known aptly as “the trench”, could quickly calculate a position or vector to within a couple of decimal places, and they did it using sliding piece of bamboo or aluminum with numbers printed on them.

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Herd Single Cell Organisms With Your Mind

May 23, 2013 by Mike Szczys 7 Comments

mind-controlled-paramecium

Most project tips involving brainwaves get passed over because it’s hard to make much out of that type of control. This project doesn’t necessarily make progress on the control side on this, but you have to admit that herding life forms with your thoughts deserves a closer look.

[Geva] set up a rig that allows him to interact with paramecium — tiny single cell organism that are happy to swim around all day long. Just like vertebrates they’re not big fans of electric shocks. Run some current through the fluid and they’ll swim toward the negative electrode.

This experiment uses four pencil leads as electrodes. These are driven by an Arduino which reacts to the input from a toy brain wave device. Concentrate in just the right way and they will swim wherever you will them to.

This isn’t quite as involved as cockroach mind control, but it’s every bit as interesting
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Comparing Desoldering Tools

April 7, 2024 by Al Williams 26 Comments

[Lee] has a Hakko FR301 desoldering gun and a Duratool knockoff. He freely admits that the Hakko is probably better, but he wonders if it’s good enough to justify being four times as expensive. He shows both of them off in a recent video that you can see below.

Often, desoldering doesn’t get as much attention as soldering, but for repairs or if you make mistakes — and who doesn’t — it is an essential skill. Many of the differences will be either good or bad, depending on your personal preference. For example, the Hakko is an all-in-one unit, so it doesn’t have a bulky box to sit on your bench. However, that also means the Hakko is larger and heavier. It also lacks controls and indicators the other unit has on the base station box.

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Hackaday Podcast Episode 251: Pluto, Pinball, Speedy Surgery, And DIY GPS

January 5, 2024 by Dan Maloney 7 Comments

Welcome to 2024! This time around, Elliot and Dan ring in a new year of awesome hacks with quite an eclectic mix. We kick things off with a Pluto pity party and find out why the tiny ex-planet deserved what it got. What do you do if you need to rename a bunch of image files? You rope a local large-language model in for the job, of course. We’ll take a look at how pinball machines did their thing before computers came along, take a fractal dive into video feedback, and localize fireworks with a fleet of Raspberry Pi listening stations. Ever wonder what makes a GPS receiver tick? The best way to find out might be to build one from scratch. Looking for some adventure? A ride on an electroluminescent surfboard might do, or perhaps a DIY “Vomit Comet” trip would be more your style. And make sure you stick around for our discussion on attempts to optimize surgery efficiency, and our look back at 2023’s top trends in the hardware world.

Grab a copy for yourself if you want to listen offline.

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Video Feedback Machine Creates Analog Fractals

January 2, 2024 by Richard Baguley 9 Comments

One of the first things everyone does when they get a video camera is to point it at the screen displaying the image, creating video feedback. It’s a fascinating process where the delay from image capture to display establishes a feedback loop that amplifies the image noise into fractal patterns. This sculpture, modestly called The God Machine II takes it to the next level, though.

We covered the first version of this machine in a previous post, but the creator [Dave Blair] has done a huge amount of work on the device since that allows him to tweak and customize the output that the device produces. His new version is quite remarkable, allowing him to create intricate fractals that writhe and change like living things.

The God Machine II is a sophisticated build with three cameras, five HD monitors, three Roland video switchers, two viewing monitors, two sheets of beam splitter glass, and a video input. This setup means it can take an external video input, capture it, and use it as the source for video feedback, then tweak the evolution of the resulting fractal image, repeatedly feeding it back into itself. The system can also control the settings for the monitor, which further changes the feedback as it evolves. [Blair] refers to this as “trapping the images.”

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The Avon Computer Goth Challenge

November 2, 2023 by Bil Herd 9 Comments

Hot off the heels of their musical debut 6502 song the good folk at the Taylor and Amy Show are at it again. This time instead of assaulting our auditory senses, they play with our perception of color all while keeping the spirit of retro computing alive.

To back up a bit, I had the pleasure of witnessing the discovery of the Avon Beauty Vision Computer while at the Vintage Computer Festival Mid-West (VCFMW) this past September. We had visited the home of our friend [Jim W] from VCFMW who nonchalantly pulled down from the shelf the reddest computer I have ever seen.

A crowd quickly gathered at this newfound treat, designed and built before the invention of the Blue LED, was fallen upon and the process of prying out its secrets began. I was not privy to the negotiations, but I did notice a brightly colored red suitcase being exfiltrated by highly trained operatives later that night.

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