A Very Accurate Current Probe

There’s many different ways of measuring current. If it’s DC, the easiest way is to use a shunt resistor and measure the voltage across it, and for AC you could use a current transformer. But the advent of the Hall-effect sensor has provided us a much better way of measuring currents. Hall sensors offers several advantages over shunts and CT’s – accuracy, linearity, low temperature drift, wider frequency bandwidth, and low insertion loss (burden) being some of them. On the flip side, they usually require a (dual) power supply, an amplification circuit, and the ability to be “zero adjusted” to null output voltage offsets.

[Daniel Mendes] needed to measure some fairly high currents, and borrowed a clip-on style AC-DC current probe to do some initial measurements for his project. Such clip on current probes are usually lower in accuracy and require output DC offset adjustments. To overcome these limitations, he then built himself an invasive hall sensor current probe to obtain better measurement accuracy (Google Translated from Portugese). His device can measure current up to 50 A with a bandwidth stretching from DC to 200 kHz. The heart of his probe is the LAH-50P hall effect current transducer from LEM – which specialises in just such devices. The 25 mV/A signal from the transducer is buffered by an OPA188 op-amp which provides a low output impedance to allow interfacing it with an oscilloscope. The op-amp also adds a x2 gain to provide an output of 50 mV/A. The other critical part of the circuit are the high tolerance shunt resistors connected across the output of the LAH-50P transducer.

The rest of his design is what appears to be a pretty convoluted power supply section. [Daniel] wanted to power his current probe with a 5V input derived from the USB socket on his oscilloscope. This required the use of a 5 V to 24 V boost switching regulator – with two modules being used in parallel to provide the desired output power. A pair of linear regulators then drop down this voltage to +15 / -15 V required for the trasducer and op-amp. His blog post does not have the board layout, but the pictures of the PCB should be enough for someone wanting to build their own version of this current sensor.

Detecting Dire Diseases – with a Selfie?

They say the eyes are the windows to the soul. But with a new smartphone app, the eyes may be a diagnostic window into the body that might be used to prevent a horrible disease — pancreatic cancer. A research team at the University of Washington led by [Alex Mariakakis] recently described what they call “BiliScreen,” a smartphone app to detect pancreatic disease by imaging a patient’s eyes.

Pancreatic cancer is particularly deadly because it remains asymptomatic until it’s too late. One early symptom is jaundice, a yellow-green discoloration of the skin and the whites of the eyes as the blood pigment bilirubin accumulates in the body. By the time enough bilirubin accumulates to be visible to the naked eye, things have generally progressed to the inoperable stage. BiliScreen captures images of the eyes and uses image analysis techniques to detect jaundice long before anyone would notice. To control lighting conditions, a 3D-printed mask similar to Google’s Cardboard can be used; there’s also a pair of glasses that look like something from [Sir Elton John]’s collection that can be used to correct for ambient lighting. Results look promising so far, with BiliScreen correctly identifying elevated bilirubin levels 90% of the time, as compared to later blood tests. Their research paper has all the details (PDF link).

Tools like BiliScreen could really make a difference in the early diagnosis and prevention of diseases. For an even less intrusive way to intervene in disease processes early, we might also be able to use WiFi to passively detect Parkinson’s.

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Ultrasonic Array Gets Range Data Fast and Cheap

How’s your parallel parking? It’s a scenario that many drivers dread to the point of avoidance. But this 360° ultrasonic sensor will put even the most skilled driver to shame, at least those who pilot tiny remote-controlled cars.

Watch the video below a few times and you’ll see that within the limits of the test system, [Dimitris Platis]’ “SonicDisc” sensor does a pretty good job of nailing the parallel parking problem, a driving skill so rare that car companies have spent millions developing vehicles that do it for you. The essential task is good spatial relations, and that’s where SonicDisc comes in. A circular array of eight HC-SR04 ultrasonic sensors hitched to an ATmega328P, the SonicDisc takes advantage of interrupts to make reading the eight sensors as fast as possible. The array can take a complete set of readings every 10 milliseconds, which is fast enough to allow for averaging successive readings to filter out some of the noise that gets returned. Talking to the car’s microcontroller over I2C, the sensor provides a wealth of ranging data that lets the car quickly complete a parallel parking maneuver. And as a bonus, SonicDisc is both open source and cheap to build — about $10 a copy.

Rather use light to get your range data? There are some pretty cheap LIDAR units on the market these days.

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Toy Dash Turned Gaming Interface

We see a lot of MAME cabinets and other gaming emulator projects here on Hackaday, but it’s not often that we see one the form factor of which so elegantly matches the ROM. [circuitbeard] converted a Tomy Turnin Turbo toy dashboard into a mini arcade machine playing Outrun.

There are many fascinating details in [circuitbeard]’s writeup. His philsophy is to “keep it looking stock” so he went to great lengths to add functionality to various elements of the toy without changing its appearance. The gear shifter was turned into a 3-way momentary switch with high and low speeds at top and bottom, with rubber bands pulling the switch back the center (neutral) when he lets go of it. The original toy’s steering wheel mounts to a slide potentiometer. The dash has a working ignition switch that uses a PowerBlock to manage the safe startup and shutdown of the Pi.  The dash also lights up the way you’d expect, and even displays accurate MPG and rev info.

For more MAME goodness here on Hackaday, see this broken tablet turned into a mini MAME cabinet or the portable MAME system of the future

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Hackaday Prize Entry: An Open Source Kiln

For his Hackaday Prize entry, [Matt] is building a small kiln for melting metals and firing clay.  He’s making this kiln out of materials anyone can acquire — dirt and a bit of nichrome wire.

Most kiln builds you’ll find on the Internet use fancy refractory bricks and other materials you may not have in your back yard. [Matt]’s project is entirely DIY, and starts with a large pile of dirt and rocks. Aftter shaking off the sifted dirt, washing the rocks, straining off the gravel, getting rid of the sand, and siphoning off the water, [Matt] has a big bag of wet clay. This clay is mixed with perlite, an insulating, refractory material, molded into bricks, and fired. The result is a brick that looks good enough to be made into a kiln.

[Matt] has already put a lot of work into the calculations required to figure out the heat transfer of this kiln. At best, this kiln is going to take 14 hours to get up to temperature. That’s incredibly slow, but then again, this kiln will be electric, and will only use 1500 Watts. That’s nothing compared to a commercial electric kiln, but it is a build [Matt] designed himself without any outside help, using only parts he can easily acquire. In any event, this is an excellent project for the Hackaday Prize.

Lu Ban’s Axe and Working with Your Chinese Suppliers

It is nearly impossible to build any kind of hardware these days without at some point in the process dealing with China — Chinese suppliers, and so by extension Chinese culture. Difficulties can be as simple as the usual inconvenience of everything stopping for weeks up to and after Chinese New Year, or engineers that you know to be otherwise reasonably competent simply choosing not to bring up glaring and obvious problems. Having encountered my share of Western hardware entrepreneurs on the verge of a breakdown, and just as many flummoxed Chinese bosses completely unable to see exactly why they’re so upset, I thought I’d try to offer at least a little insight into one of the many issues that comes up.

Nearly any school child in the world will be able to tell you whom they were taught invented the lightbulb, the telephone, the radio transmitter. Those same children will usually be able to tell you of at least a few Chinese inventions as well — gunpowder, paper, the compass etc. But with one key difference, even the Chinese children are unlikely to be able to credit even a group of people for their invention let alone a single (usually misattributed) individual.

China does not really have an Edison, or Tesla, or Bell — oh we’ve had people as brilliant, but they are not celebrated in quite the same way for cultural reasons. If you were to do an alternate history of China where we went through the Industrial Revolution first, you’d want to split the timeline around Mozi (墨子). The Mohists (followers of Mozi) had advanced siege engine design, schools of logic, mathematics and theory for the physical sciences. much of the same foundation that set the West on its particular trajectory. In the end, Confucian ideals won out and China became a culture that celebrated scholarship over ingenuity (to vastly oversimplify things).

Even our respective terms for engineer reflect this. The word engineer (Latin ingeniator) is derived from the Latin words ingeniare (“to contrive, devise”) and ingenium (“cleverness”). Yet in Chinese 工程师, the first character for engineer in Chinese is the carpenters square 工. He or she is a simple worker (工人 literally “Work Person”). Even now, engineers are not held in anywhere near the same regard in China as they are in the West.

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Friday Hack Chat: Making in Shenzhen

China is an amazing land of opportunity, and if you want to build anything, you can build it in Shenzhen. This city that was just a small fishing village a few decades ago has grown into a cyberpunk metropolis of eleven million and has become the manufacturing capital of the world. You’re probably reading this on a device made somewhere around Shenzhen.

For this week’s Hack Chat, we’re going to be talking about manufacturing in Shenzhen. We’re bringing in a very special guest for this one: [Naomi Wu] is a Cantonese DIY maker, professional web dev, transhumanist, electronics reviewer, occasional Hackaday contributor, vlogger, 3D printerer, advocate of women in STEM, SexyCyborg, and a riot on Twitter. [Naomi] also lives and works in Shenzhen, and is tapped into the DIY and maker culture there. She’s created 3D printed pen testing shoes, a Raspberry Pi cosmetics case, and infinity skirts.

This Friday (or Saturday, depending on which side of the date line you’re on), [Naomi] is going to be talking about manufacturing, making, DIY, and Shenzhen culture. Of particular interest will be electronics purchasing and manufacturing in Shenzhen, designing wearable projects with an emphasis on power and thermal design, documenting projects, and Shenzhen culture. This is basically an AMA, so if you have any questions you’d like to ask, throw them up in this spreadsheet.

Here’s How To Take Part:

join-hack-chatOur Hack Chats are live community events on the Hackaday.io Hack Chat group messaging. Hack Chats are usually at noon, Pacific time on Friday. This week we’re doing the Hack Chat a little later, because timezones. This week’s Hack Chat will be at 6 pm PDT Friday / 9 am CST Saturday. Confused? Here’s a time and date converter!

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on Hackaday.io

You don’t have to wait until Friday; join whenever you want and you can see what the community is talking about.