Custom Dummy Load With Data Logging

March 15, 2021 by Bryan Cockfield 10 Comments

While it might seem counterintuitive on the surface, there are a number of cases where dumping a large amount of energy into a resistor simply to turn it into heat is necessary to the operation of a circuit. Most of these cases involve testing electronic equipment such as power supplies or radio transmitters and while a simple resistor bank can be used in some situations, this active dummy load is comprised of different internals has some extra features to boot.

The load bank built by [Debraj] is actually an electronic load, which opens it up for a wider set of use cases than a simple passive dummy load like a resistor bank. It’s specifically designed for DC and also includes voltage measurement, current control, and temperature measurement and speed control of the fans on the heat sinks. It also includes a Bluetooth module that allows it to communicate to a computer using python via a custom protocol and GUI.

While this one does use a case and some other parts from another product and was specifically built to use them, the PCB schematics and code are all available to build your own or expand on this design. It’s intended for DC applications, but there are other dummy loads available for things such radio antenna design, and it turns out that you can learn a lot from them too.

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Tetris On Split-Flap Go Brrr

March 7, 2021 by Kristina Panos 9 Comments

It hardly seems possible, but engineer collective and split-flap display purveyors [Oat Foundry] were able to build a working implementation of Tetris on a 10 x 40 split-flap display in the span of a single day. Check it out in the video after the break.

This project is a bit understaffed in the details department, but we do know that [Oat Foundry] started with [Timur Bakibayev]’s open-source implementation of Tetris in Python and modified the draw function to work on a split-flap display. As you may have guessed, the biggest obstacle is the refresh rate and how it affects playability — particularly during those tense moments when a player rotates a piece before dropping it. Split-flaps flip quickly from on to off, but flipping back to on requires a full trip around through all the other characters.

We think this is nice work for a one-day build. Should they go further, we’d like to see the same things implemented as [Oat Foundry] does: a high score tracker and a preview of the next piece.

Don’t have a split-flap display? Yeah, us either, but we do have televisions. Turn on the tube and check out this Nano-scale Tetris.

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Circuit Impedance Calculations Without Cumbersome Simulations

March 2, 2021 by Bryan Cockfield 11 Comments

Using circuit simulating software like SPICE can be a powerful tool for modeling the behavior of a circuit in the real world. On the other hand, it’s not always necessary to have all of the features of SPICE available all the time, and these programs tend to be quite expensive as well. To that end, [Wes Hileman] noticed an opportunity for a specific, quick method for performing impedance calculations using python without bulky, expensive software and came up with a program which he calls fastZ.

The software works on any network of passive components (resistors, capacitors, and inductors) and the user can specify parallel and series connections using special operators. Not only can the program calculate the combined impedance but it can perform frequency analysis at a specified frequency or graph the frequency response over a wide range of frequencies. It’s also running in python which makes it as simple as importing any other python package, and is also easy to implement in any other python program compared to building a simulation and hoping for the best.

If you find yourself regularly drawing Bode plots or trying to cobble together a circuit simulation to work with your python code, this sort of solution is a great way to save a lot of headache. It is possible to get the a piece of software like SPICE to to work together with other python programs though, often with some pretty interesting results.

Python Settles Bet About Best Strategy In Children’s Board Game

February 21, 2021 by Donald Papp 17 Comments

Simulating a tabletop game can be done for several reasons: to play the game digitally, to create computer opponent(s), or to prove someone wrong. In [Everett]’s case, he used Python to prove which adult was right about basic strategy in a children’s game.

[Everett]’s 5-year-old loves a simple game called Hoot Owl Hoot! in which players cooperatively work to move owls along a track to the safety of a nest. Player pieces move on spaces according to the matching colors drawn from a deck of cards. If a space is already occupied, a piece may jump ahead to the next available spot. The game has a bit more to it than that, but those are the important parts. After a few games, the adults in the room found themselves disagreeing about which strategy was optimal in this simple game.

It seemed to [Everett] that it was best to move pieces in the rear, keeping player pieces grouped together and maximizing the chance of free moves gained by jumping over occupied spaces. [Everett]’s wife countered that a “longest move” strategy was best, and one should always select whichever piece would benefit the most (i.e. move the furthest distance) from any given move. Which approach wins games in the fewest moves? This small Python script simulates the game enough to iteratively determine that the two strategies are quite close in results, but the “longest move” strategy does ultimately come out on top.

As far as simulations go, it’s no Tamagotchi Singularity and [Everett] admits that the simulation isn’t a completely accurate one. But since its only purpose is to compare whether “no stragglers” or “longest move” wins in fewer moves, shortcuts like using random color generation in place of drawing the colors from a deck shouldn’t make a big difference. Or would it? Regardless, we can agree that board games can be fitting metaphors for the human condition.

Interfacing A Z80 CPU With The Raspberry Pi

February 9, 2021 by Lewin Day 25 Comments

The Z80 was a big deal in the 1970s and 1980s, and while its no longer a dominant architecture today, its legacy lives on. [James Andrew Fitzjohn] is a fan of the Z, and decided to interface the real silicon with the Raspberry Pi, by and large for the fun of it!

The Z80’s address and data lines, as well as the clock, are hooked up to the Raspberry Pi through several MCP23017 GPIO expanders. The Pi’s GPIO lines aren’t known for their speed, of course, and using expanders through I2C isn’t exactly quick either. However, speed isn’t necessary, as the clock only goes as fast as the Raspberry Pi desires, since it’s controlling the clock along with everything else. There’s also an LCD for viewing the Z80s status, along with some era-appropriate blinkenlights.

This setup allows the Pi to run code directly on the Z80 itself, while managing the CPU’s RAM in its own memory, all through a Python script. It’s a fun hack that lets you run retro code on retro silicon without using an emulator. Techniques like these are useful for finding undocumented or edge case performance of a processor. If this hack isn’t enough Zilog for your liking, consider throwing one in your pocket as well!

Decoding NOAA Satellite Images In Python

January 27, 2021 by Tom Nardi 10 Comments

You’d be forgiven for thinking that receiving data transmissions from orbiting satellites requires a complex array of hardware and software, because for a long time it did. These days we have the benefit of cheap software defined radios (SDRs) that let our computers easily tune into arbitrary frequencies. But what about the software side of things? As [Dmitrii Eliuseev] shows, decoding the data satellites are beaming down to Earth is probably a lot easier than you might think.

Well, at least in this case. The data [Dmitrii] is after happens to be broadcast from a relatively old fleet of satellites operated by the National Oceanic and Atmospheric Administration (NOAA). These birds (NOAA-15, NOAA-18 and NOAA-19) are somewhat unique in that they fly fairly low and utilize a simple analog signal transmitted at 137 MHz. This makes them especially good targets for hobbyists who are just dipping their toes into the world of satellite reception.

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Raspberry Pi Zero Powers Spotify Streaming IPod

January 27, 2021 by Tom Nardi 32 Comments

Even those critical of Apple as a company have to admit that they were really onto something with the iPod. The click wheel was a brilliant input device, and the simplicity of the gadget’s user interface made it easy to get to the music you wanted with a minimum of hoop jumping. Unfortunately it was a harbinger of proprietary software and DRM, but eventually there were a few open source libraries that let you put songs on the thing without selling your soul to Cupertino.

Of course, modern users expect a bit more than what the old hardware can deliver. Which is why [Guy Dupont] swapped the internals of his iPod Classic with a Raspberry Pi Zero W. This new Linux-powered digital audio player is not only capable of playing essentially any audio format you throw at it, but can also tap into streaming services such as Spotify. But such greatness doesn’t come easy; to pull this off, he had to replace nearly every component inside the player with the notable exception of the click wheel itself. Good thing the Classics were pretty chunky to begin with.

In addition to the Pi Zero running the show, he also had to fit a 1000 mAh battery, its associated charging and boost modules, a vibration motor for force feedback, and a 2″ LCD from Adafruit. The display ended up being almost the perfect size to replace the iPod’s original screen, and since it uses composite video, only took two wires to drive from the Pi. To interface with the original click wheel, [Guy] credits the information he pulled from a decade-old Hackaday post.

Of course with a project like this, the hardware is only half the story. It’s one thing to cram all the necessary components inside the original iPod enclosure, but by creating such an accurate clone of its iconic UI in Python, [Guy] really took things to the next level. Especially since he was able to so seamlessly integrate support for Spotify, a feature the Apple devs could scarcely have imagined back at the turn of the millennium. We’re very interested in seeing the source code when he pushes it to the currently empty GitHub repository, and wouldn’t be surprised if it set off a resurgence of DIY iPod clones.

We’ve seen modern hardware grafted onto the original iPod mainboard, and over the years a few hackers have tried to spin up their own Pi-based portable music players. But this project that so skillfully combines both concepts really raises the bar.

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