Escape Cable Hell with an Audio I/O Multiplexer

If you ever find yourself swapping between a mix of audio inputs and outputs and get tired of plugging cables all the time, check out [winslomb]’s audio multiplexer with integrated amplifier. The device can take any one of four audio inputs, pass the signal through an amplifier, and send it to any one of four outputs.

The audio amplifier has a volume control, and the inputs and outputs can be selected via button presses. An Arduino Pro Mini takes care of switching the relays based on the button presses. On the input side, you can plug in devices like a phone, TV, digital audio player or a computer. The output can be fed to speakers, headsets or earphones.

At the center of the build lies a TI TPA152 75-mW stereo audio power amplifier. This audio op-amp is designed to drive 32 ohm loads, so performance might suffer when connecting it to lower impedance devices, but it seems to work fine for headphones and small computer speakers. The dual-gang potentiometer controls the volume, and the chip has a useful de-pop feature. The circuit is pretty much a copy of the reference shown in the data sheet. Switching between inputs or outputs is handled by a bank of TLP172A solid state relays with MOSFET outputs, and it’s all tied together with a micro-controller, allowing for WiFi or BLE functionality to be added on later.

[winslomb] laid out the design using Eagle and he made a couple of footprint mistakes for the large capacitors and the opto-relays. (As he says, always double-check part footprints!) In the end, he solder-bridged them on to the board, but they should probably be fixed for the next revision.

[winslomb] built the switch as his capstone project while on his way to getting a Masters in EE, and although the device did function as required, there is still room for improvement. The GitHub repository contains all the hardware and software sources. Check out the video below where he walks through a demo of the device in action. If you are looking for something simpler, here is a two input – one output audio switcher with USB control and on the other end of the spectrum, here’s an audio switch that connects to the Internet.

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Hack The Steam Controller?

[willrandship] sent in a conversation from Reddit discussing the programming ports inside the Steam controller and their potential for hacking. From the posts and the pictures it seems the radio/SoC and the MCU can be programmed on the board, or at least they both have JTAG headers. The JTAG headers are in the form of “Tag-Connect” pads on the board so it will require the dedicated cable or soldering some hardware to the board temporarily.

From the pictures we can see a NXP LPC11U37F ARM Cortex-M0 and a Nordic nRF51822 ARM Cortex-M0 SoC with integrated Bluetooth low energy. There are only a limited number of Steam Controllers in the wild at this time so we don’t expect much in the way of hacking them thus far. There is a Steam Controller hackaday.io project just started for anyone who would like to contribute to the Steam Controller hacking.

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Dalek-Berry-Pi Mower

There’s something about lawn mowers and hackers. A desire to make them into smart, independent robots. Probably in preparation for the day when Skynet becomes self-aware or the Borg collective comes along to assimilate them into the hive. [Ostafichuk] wanted his to be ready when that happens, so he’s building a Raspberry-Pi powered, Dalek costumed Lawn Mower that is still a work in progress since starting on it in 2014. According to him,  “commercial robot lawn mowers are too expensive and not nearly terrifying enough to be any fun, so I guess I will just have to build something myself…”

His first report describes the basic skeletal structure he built using scrap pieces of wood. Two large lawn tractor wheels and a third pivot wheel help with locomotion. The two large wheels are driven by geared motors originally meant for car seat height adjustments. A deep cycle 12V battery, and solar panels for charging would take care of power. A raspberry-pi provides the brain power for the Dalek-Mower and L298N based drivers help drive the motors. The body was built from some more planks of scrap wood that he had lying around. While waiting around for several parts to arrive – ultrasonic sensors, accelerometer, 5V power supply modules – he started to paint and decorate the wood work. Generous amounts of water repellent paint and duct tape were used to make it weather proof. His initial plan was to use python for the code, but he later switched to programming in c along with wiringPi library. Code for the project is available from his bitbucket git repository. Load testing revealed that the L298N drivers were not suitable for the high current drawn by the motors, so he changed over to relays to drive them.

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Tracking the Hamster Marathon

[Michelle Leonhart] has two Roborovski hamsters (which, despite the name, are organic animals and not mechanical). She discovered that they seem to run on the hamster wheel all the time. A little Wikipedia research turned up an interesting factoid: This particular breed of hamster is among the most active and runs the equivalent of four human marathons a night. Of course, we always believe everything we read on Wikipedia, but not [Michelle]. She set out to determine if this was an accurate statement.

She had already added a ball bearing to the critters’ wheel to silence it by cannibalizing an old VCR. What she needed was the equivalent of a hamster pedometer. A Raspberry Pi and a Hall effect sensor did the trick. At least for the raw measurement. But it still left the question: how much distance is a hamster marathon?

01_hamster_stride_measurement[Michelle] went all scientific method on the question. She determined that an average human female’s stride is 2.2 feet which works out to 2400 strides per mile. A marathon is 26.2 miles (based on the distance Pheidippides supposedly ran to inform Athens of victory after the battle of Marathon). This still left the question of the length of a hamster’s stride. Surprisingly, there was no definitive answer, and [Michelle] proposed letting them run through ink and then tracking their footsteps. Luckily, [Zed Shaw] heard about her plan on Twitter and suggested pointing a webcam up through the plastic bottom of the cage along with a scale. That did the trick and [Michelle] measured her hamster’s stride at about 0.166 feet (see right).

Now it was a simple matter of math to determine that a hamster marathon is just under 10,500 steps. Logging the data to SQLite via ThingSpeak for a month led [Michelle] to the conclusion: her hamsters didn’t run 4 marathon’s worth of steps in a night. In fact, they never really got much over 2 marathons.

Does [Michelle] have lazy hamsters, or did she just add to our body of scientific knowledge about rodents? We don’t know. But we couldn’t help but admire her methods and her open source data logging code would probably be useful for some non-hamster activities.

If you are super competitive, you could use [Michelle’s] data to handicap yourself and challenge your pets to a race. But it would probably be cooler to build them their own Starship Trooper-style walkers. Either way, you can check out [Michelle’s] little marathon runners in the video below.

The Eloquence of the Barcode

Beep. You hear it every time you buy a product in a retail store. The checkout person slides your purchase over a scanner embedded in their checkout stand, or shoots it with a handheld scanner. The familiar series of bars and spaces on the label is digitized, decoded to digits, and then used as a query to a database of every product that particular store sells. It happens so often that we take it for granted. Modern barcodes have been around for 41 years now. The first product purchased with a barcode was a 10 pack of Juicy Fruit gum, scanned on June 26, 1974 at Marsh supermarket in Troy, Ohio. The code scanned that day was UPC-A, the same barcode used today on just about every retail product you can buy.

The history of the barcode is not as cut and dry as one would think. More than one group has been credited with inventing the technology. How does one encode data on a machine, store it on a physical media, then read it at some later date? Punch cards and paper tape have been doing that for centuries. The problem was storing that data without cutting holes in the carrier. The overall issue was common enough that efforts were launched in several different industries.

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Stellarator is Germany’s Devilishly Complex Nuclear Fusion

You may not have heard of a Stellarator before, but if all goes well later this month in a small university town in the far northeast of Germany, you will. That’s because the Wendelstein 7-X is finally going to be fired up. If it’s able to hold the heat of a fusion-capable plasma, it could be a huge breakthrough.

So what’s a stellarator? It’s a specific type of nuclear fusion containment geometry that, while devilishly complex to build and maintain, stands a chance at being the first fusion generator to achieve break-even, where the energy extracted from the fusion reaction is greater or equal to the energy used in creating the necessary hot plasma.

There’s an awesome video on the W7-X, and some of the theory behind the reactor just below the break.

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Making the Case For Nuclear Aircraft

At any given moment, several of the US Navy’s Nimitz class aircraft carriers are sailing the world’s oceans. Weighing in at 90 thousand tons, these massive vessels need a lot of power to get moving. One would think this power requires a lot of fuel which would limit their range, but this is not the case. Their range is virtually unlimited, and they only need refueling every 25 years. What kind of technology allows for this? The answer is miniaturized nuclear power plants. Nimitz class carriers have two of them, and they are pretty much identical to the much larger power plants that make electricity. If we can make them small enough for ships, can we make them small enough for other things, like airplanes?

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