XFM: A 32-Voice Polyphonic FM Synthesizer On An FPGA

July 24, 2019 by Maya Posch 27 Comments

There’s something about Frequency Modulation (FM) synthesizer chips that appeals to a large audience. That’s one of the reasons behind [René Ceballos]’s XFM project, aiming to duplicate on an FPGA the sound of pure-FM synthesizer chips of the past such as the Yamaha DX series, OPL chip series and TX81Z/802/816. The result is a polyphonic, 32-voice, 6-operator FM synthesizer stereo module.

The project page goes into a lot of detail about the design choices which ultimately led to XFM being implemented on an FPGA, instead of using a dedicated DSP or MCU. Coming from the world of virtual synthesizers running on PCs, [René ]’s first impulse was to implement something on a Raspberry Pi or equivalent. Unfortunately these boards require a lot of power (ruling out battery-powered operation) and can hardly be called real-time, which led [René ] to abandon this attempt.

The design choice against the use of an MCU is simple: though capable of real-time processing, they lack the necessary power to make them a good choice for audio-processing. Working through the calculations to determine what kind of processing power would be needed, it was found that around 650 MIPS would be needed, a figure which most MCUs struggle to achieve a fraction of.

As one of the further requirements for XFM was that it should be as cheap as possible, this ruled out as too expensive the DSP chips which do have the power and hardware features needed. The component chosen was a Xilinx Spartan 6 FPGA, which though somewhat infamous and shunned in FPGA circles turns out to be a very economical option for this project.

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Tea Bot Solves Another First World Problem

July 24, 2019 by Al Williams 19 Comments

In the movie Wall-E, future humans live in floating chairs and have everything done for them. Today, we grumble if we have to go to physically find a light switch or a remote control. How far away can floating chairs with screens be? T2, the Tea Bot, gets us one step closer to that. Using a laser-cut frame, an ESP8266, and a servo motor, the T2 brews your tea for exactly the right amount of time.

We were kind of hoping the robot would at least dunk the tea bag in and out, but it does provide a web interface that lets you select the brew. Of course, the code is available, so you could make modifications — maybe turn on a hotplate underneath the cup.

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Reaction Trainer Keeps You On Your Toes

July 24, 2019 by Lewin Day 1 Comment

In many sports, it’s important for competitors to be light on their feet, and able to react quickly to external stimuli. It all helps with getting balls in goals, and many athletes undergo reaction drills as part of their training regime. To help with this, [mblaz] set out to build a set of reaction trainers.

The training setup consists of a series of discs, each with glowing LEDs and a proximity sensor. The discs randomly light up, requiring a touch or wave to switch them off. At this point, another disc will light randomly, and so on.

The discs are built using an ATmega328 to run the show, with NRF24L01+ radios used to communicate between the modules. High brightness red LEDs are used for indication. An optical proximity sensor is used for its fast reaction time and low cost, while power comes via a small lithium polymer battery integrated into each disc.

We’re sure [mblaz] and his fellow athletes will find the rig to be useful in their training. There’s plenty of scope for electronics to help out with athletic training; this boxing trainer is a great example. If you’ve got a great sports engineering project of your own, don’t hesitate to send it in!

Shower Water Monitor Tracks The Dollars And Cents

July 24, 2019 by Lewin Day 27 Comments

There’s nothing quite as relaxing as a long, hot shower. This has the tendency of making the bather absent minded as to the amount of water being used, which can lead to excessive bills. [LiamOSM] built a device to monitor this instead, and calculate the cost, to boot.

The device consists of an Arduino hooked up to a cheap flow meter sourced from Banggood. The sensor consists of a paddle wheel that sits in the water flow, fitted with a magnet. A hall effect sensor picks up pulses as the magnet spins, and counting these allows the flow rate to be measured. An HD44780 LCD screen is used to display the readings, controlled over I²C.

To avoid issues in the bathroom environment, the enclosure was designed to be waterproof. The LCD is mounted behind a clear plastic window sourced from vegetable packaging, and the button chosen was specially selected for its sealing grommets. We’d love to see a proper submersion test, but for the most part, it appears to be doing a good job in the bathroom.

If you’re interested in monitoring your water use as a household, you might find it possible to piggy back on the municipal meter.

An Open Hardware Rubber Ducky

July 24, 2019 by Tom Nardi 12 Comments

No it’s not an open source version of Bert’s favorite bathtime toy (though seriously, let us know if you see one), the PocketAdmin by [Radik Bechmetov] is intended to be an alternative to the well-known “USB Rubber Ducky” penetration testing tool from Hak5. It might look like a standard USB flash drive, but underneath that black plastic enclosure is a whole lot of digital mischief waiting to spill out.

The general idea is that the PocketAdmin appears to the host computer as either a USB Human Interface Device (keyboard, mouse, etc) or a USB Mass Storage Device. In either event, the user has the ability to craft custom payloads which can exploit the operating system’s inherent trust in locally connected devices. The most common example is mimicking a USB keyboard that starts “typing” once connected to the computer.

You can even configure what vendor and product IDs the PocketAdmin advertises, allowing you to more accurately spoof various devices. [Radik] has included some other interesting features, such as the ability to launch different payloads depending on the detected operating system. That way it won’t waste time trying to bang out Windows commands when it’s connected to a Linux box.

The hardware is designed to be as easy and cheap to replicate as possible. The heavy lifting is done by a STM32F072C8T6 microcontroller, coupled with a W25Q256FVFG 32MiB flash chip to store the payloads. Beyond that, the BOM consists mainly of passives and a few obvious bits like the male USB connector. [Radik] has even provided a link to where you can buy the convincing looking USB “flash drive” enclosure.

We’ve seen low-cost DIY versions of the USB Rubber Ducky in the past, but PocketAdmin is interesting in that it seems like [Radik] is looking to break new ground with this project rather than just copy what’s already been done. This will definitely be one to watch as the 2019 Hackaday Prize heats up.

Printed It: Hand Cranked Photography Turntable

July 24, 2019 by Tom Nardi 21 Comments

Even a relatively low-end desktop 3D printer will have no problems running off custom enclosures or parts for your latest project, and for many, that’s more than worth the cost of admission. But if you’re willing to put in the time and effort to become proficient with necessary CAD tools, even a basic 3D printer is capable of producing complex gadgets and mechanisms which would be extremely time consuming or difficult to produce with traditional manufacturing techniques.

Once you find yourself at this stage of your 3D printing career, there’s something of a fork in the road. The most common path is to design parts which are printed and then assembled with glue or standard fasteners. This is certainly the easiest way forward, and lets you use printed parts in a way that’s very familiar. It can also be advantageous if you’re looking to meld your own printed parts with existing hardware.

The other option is to fully embrace the unique capabilities of 3D printing. Forget about nuts and bolts, and instead design assemblies which snap-fit together. Start using more organic shapes and curves. Understand that objects are no longer limited to simple solids, and can have their own complex internal geometries. Does a hinge really need to be two separate pieces linked with a pin, or could you achieve the desired action by capturing one printed part inside of another?

If you’re willing to take this path less traveled, you may one day find yourself creating designs such as this fully 3D printed turntable by Brian Brocken. Intended for photographing or 3D scanning small objects without breaking the bank, the design doesn’t use ball bearings, screws, or even glue. Every single component is printed and fits together with either friction or integrated locking features. This is a functional device that can be printed and put to use anywhere, at any time. You could print one of these on the International Space Station and not have to wait on an order from McMaster-Carr to finish it.

With such a clever design, I couldn’t help but take a closer look at how it works, how it prints, and perhaps even some ways it could be adapted or refined going forward.

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A PKE Meter That Actually Detects Radiation

July 24, 2019 by Lewin Day 5 Comments

Fans of Ghostbusters will remember the PKE meter, a winged handheld device capable of detecting supernatural activity. Precious little technical data on the device remains, leaving us unable to replicate its functionality. However, the flashing, spreading wings serve as a strong visual indicator of danger, and [mosivers] decided this would be perfect for a Geiger counter build.

An SBM20 Geiger tube serves as the detection device, hooked up to an Arduino Nano. An OLED display is used to display the numerical data to the user. The enclosure and folding wings are 3D printed, and fitted with 80s-style yellow LEDs as per the original movie prop.

The device is quite intuitive in its use – if the wings flare out and the lights are flashing faster, you’re detecting an increased level of radiation. In a very real sense, it makes using a Geiger counter much more straightforward for the inexperienced or the hearing impaired. Naturally, there’s also a buzzer generating the foreboding clicks as you’d expect, too.

Geiger counters are a popular project, though we hope they don’t become common household items in the near future. Here’s a Fallout-inspired build for fans of the game. Video after the break.

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