Measuring The Cooling Effect Of Transformer Oil

November 15, 2018 by Steven Dufresne 36 Comments

Transformer oil has long served two purposes, cooling and insulating. The large, steel encased transformers we see connected to the electrical grid are filled with transformer oil which is circulated through radiator fins for dumping heat to the surrounding air. In the hacker world, we use transformer oil for cooling RF dummy loads and insulating high voltage components. [GreatScott] decided to do some tests of his own to see just how good it is for cooling circuits.

He started with testing canola oil but found that it breaks down from contact with air and becomes rancid. So he purchased some transformer oil. First, testing its suitability for submerging circuits, he found that he couldn’t see any current above his meter’s 0.0 μA limit when applying 15 V no matter how close together he brought his contacts. At 1 cm he got around 2 μA with 230 VAC, likely from parasitic capacitance, for a resistance of 115 Mohm/cm.

Moving on to thermal testing, he purchased a 4.7 ohm, 100 watt, heatsink encased resistor and attached a temperature probe to it with Kapton tape. Submerging it in transformer oil and applying 25 watts through it continuously, he measured a temperature of 46.8°C after seven minutes. The same test with distilled water reached 35.3°C. Water’s heat capacity is 4187 J/kg∙K, not surprisingly much better than the transformer oil’s 2090 J/kg∙K which in turn is twice as good as air’s 1005 J/kg∙K.

He performed a few more experiments but we’ll leave those to his video below.

We’ve run across a number of tests running boards submerged in various oils before. For example, we’ve seen Raspberry Pi’s running in vegetable oil and mineral oil as well as an Arduino running in a non-conductive liquid coolant, all either overclocked or under heavy load.

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Foam Airboat Is Cheap RC Fun

November 15, 2018 by Lewin Day 7 Comments

Archer fans and residents of Louisiana will already be familiar with the concept of the airboat. Put a powerful engine running an aircraft prop on a flat-bottomed hull, and you’ve got an excellent way to traverse the marshes of the American South. While a fully-fledged airboat might run you the best part of $100,000, this no-frills radio-controlled version is great fun at a much lower price.

The hull is built on a sheet of foam, which is cheap, readily available, and suitably buoyant for the task. It’s then kitted out with a brushless motor to run the prop and a servo to control the rudder. Lace it up with a radio receiver and speed controller and you’re good to go.

The build could readily be completed in well under a couple of hours, and is a great one to tackle with kids due to its mechanical simplicity. There’s room for extra creativity too – you can always substitute a watermelon if you’re feeling peckish. Video after the break. Continue reading “Foam Airboat Is Cheap RC Fun” →

Researchers Seek To Create The Digital Smell Interface

November 15, 2018 by Drew Littrell 18 Comments

We hear digital audio, we see digital video, and we feel digital haptic feedback. However, we don’t have an analog for the sense of smell. [Kasun] and his team of researchers from the Imagineering Institute in Malaysia are in the midst of changing that reality. Their project aims to transmit fragrances via electronic stimulation. Though it’s really more of a step toward creating a multi-sensory internet.

The team’s “electric smell machine” consists of a variable power supply connected to silver electrodes wrapped around an endoscopic camera. The camera is necessary to ensure contact with the user’s olfactory bulb as electric current pulses through the electrodes. The current values vary based upon the scent being replicated and are in the 0.2mA neighborhood. Early trials of the machine have revealed that around one-quarter of test subjects are able to identify the smells being replicated. They reported smells being fruity, sweet, and woody though all had a chemical-like odor attached.

The concept of “smell-o-vision” is not a new one, as it has been around longer than motion pictures with sound. Previous attempts at accompanying film and television with scent have been a result of chemical reactions. Devices from these types of experiments typically involved cartridges that would need to be replaced when the chemical substances were depleted. [Kasun]’s team approach is to avoid the chemical approach in favor of directly stimulating the olfactory receptors. Those interested in the gritty details can read the research paper on digitizing smell.

[Kasun] and his team uploaded a video on the project that you can view below. It’s all a work in progress at this point, but sign me up for a trial when they pinpoint the true essence of new car smell.

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An In-Depth Look At Dexter, The Robotic Arm

November 15, 2018 by Elliot Williams 25 Comments

Dexter, a really great robot arm project, just won top honors in the 2018 Hackaday Prize, and walked away with $50,000 toward continuing their project. As a hat tip to Hackaday and the community, Haddington Dynamics, the company behind Dexter, agreed to open-source their newest version of Dexter as well. As James Newton said when accepting the trophy during the award ceremony, “because of your faith in us, because of this award, we have been moved to open-source the next generation of Dexter.” Some very clever work went into producing Dexter, and we can’t wait to see what further refinements have been made!

Dexter isn’t the only robotic arm in town, by any means. But in terms of hobbyist-level robotics, it’s by far the most complete robot arm that we’ve seen, and it includes a couple of design features that make both its positional accuracy and overall usability stand out above the rest. This is a robot arm with many of the bells and whistles of a hundred-thousand dollar robot, but on a couple-thousand dollar budget. Continue reading “An In-Depth Look At Dexter, The Robotic Arm” →

Adding Linux To A PDP-11

November 15, 2018 by Brian Benchoff 14 Comments

The UNIBUS architecture for DEC’s PDPs and Vaxxen was a stroke of genius. If you wanted more memory in your minicomputer, just add another card. Need a drive? Plug it into the backplane. Of course, with all those weird cards, these old UNIBUS PDPs are hard to keep running. The UniBone is the solution to this problem. It puts Linux on a UNIBUS bridge, allowing this card to serve as a memory emulator, a test console, a disk emulator, or any other hardware you can think of.

The key to this build is the BeagleBone, everyone’s second-favorite single board computer that has one feature the other one doesn’t: PRUs, or a programmable real-time unit, that allows you to blink a lot of pins very, very fast. We’ve seen the BeagleBone be used as Linux in a terminal, as the rest of the computer for an old PDP-10 front panel and as the front end for a PDP-11/03.

In this build, the Beaglebone’s PRU takes care of interfacing to the UNIBUS backplane, sending everything to a device emulator running as an application. The UniBone can be configured as memory or something boring, but one of these can emulate four RL02 drives, giving a PDP-11 an amazing forty megabytes of storage. The real killer app of this implementation is giving these emulated drives a full complement of glowing buttons for load, ready, fault, and write protect, just like the front of a real RL02 drive. This panel is controlled over the I2C bus on the Beaglebone, and it’s a work of art. Of course, emulating the drive means you can’t use it as the world’s largest thumb drive, but that’s a small price to pay for saving these old computers.

Choosing Cell Modems: The Drama Queen Of Hardware Design

November 15, 2018 by Kerry Scharfglass 20 Comments

So you went to a tradeshow and heard about this cool new idea called the Internet Of Things; now it’s time to build an IoT product of your own. You know that to be IoT, your Widget D’lux® has to have a network connection but which to choose?

You could use WiFi or Bluetooth but that would be gauche. Maybe LoRaWAN? All the cool kids are using LoRa for medium or long range wireless these days, but that still requires a base station and Widget D’lux® will be a worldwide phenomenon. Or at least a phenomenon past your bedroom walls. And you know how much user’s hate setting things up. So a cell modem it is! But what do you have to do to legally include one in your product? Well that’s a little complicated.

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Cyborg Mushrooms

November 15, 2018 by Brian McEvoy 3 Comments

Of all the fictional cyborgs who turn against humanity to conquer the planet, this is as far from that possibility as you can get. These harmless mushrooms seem more interested in showing off their excellent fashion sense with a daring juxtaposition of hard grid lines with playful spirals. But the purpose of this bacteria-fungus-technology hybrid is to generate electricity. The mushrooms are there to play nurse to a layer of cyanobacteria, the green gel in the photo, while the straight black lines harvest electricity.

Cyanobacteria do not live very long under these kinds of conditions, so long-term use is out of the question, but by giving the cyanobacteria somewhere it can thrive, the usefulness grows. The interplay between bacterial and supportive organics could lead to advances in sensors and hydrogels as well. At some point, we may grow some of our hardware and a green thumb will be as useful as a degree in computer science.

Hydrogels could be the next medical revolution, and we’ve already made hydrogels into tattoos, used them as forms for artificial muscles, and hydrogels can be a part of soft tissue printing.