The 4-20 MA Current Loop

July 19, 2017 by 114 Comments

The I/O capabilities built into most microcontrollers make it easy to measure the analog world. Say you want to build a data logger for temperature. All you need to do is get some kind of sensor that has a linear voltage output that represents the temperature range you need to monitor — zero to five volts representing 0° to 100°C, perhaps. Hook the sensor up to and analog input, whip up a little code, and you’re done. Easy stuff.

Now put a twist on it: you need to mount the sensor far from the microcontroller. The longer your wires, the bigger the voltage drop will be, until eventually your five-volt swing representing a 100° range is more like a one-volt swing. Plus your long sensor leads will act like a nice antenna to pick up all kinds of noise that’ll make digging a usable voltage signal off the line all the harder.

Luckily, industrial process engineers figured out how to deal with these problems a long time ago by using current loops for sensing and control. The most common standard is the 4-mA-to-20-mA current loop, and here we’ll take a look at how it came to be, how it works, and how you can leverage this basic process control technique for your microcontroller projects.

Continue reading “The 4-20 MA Current Loop” →

Friday Hack Chat: Making Electronics For Education

July 19, 2017 by 5 Comments

For this week’s Hack Chat on Hackaday.io, we’ll be talking with AnnMarie Thomas about making electronics for education. There’s a huge intersection between electronics and education, and whether you’re designing robots for a FIRST team or designing a geometry curriculum around 3D-printed objects, there’s a lot electronics can teach students.

AnnMarie Thomas is an associate professor at the School of Engineering and the Opus College of Business at the University of St. Thomas. She’s the founder of the Playful Learning Lab, and along with her students she’s created Squishy Circuits. AnnMarie is the author of Making Makers: Kids, Tools, and the Future of Innovation. Basically, if you’re looking for someone who knows how to make an educational product, you can’t do any better.

For this week’s Hack Chat, we’ll be talking about how to define how technology and education can intersect. There are ways to define a concept, build and sell an educational product, and how to find a market for a product. If you’ve ever wanted to know what goes into getting students to dive into electronics, this is the Hack Chat you have to sit in on.

Oh, AnnMarie is also a judge for this year’s Hackaday Prize. Neat.

Also on deck for this week’s Hack Chat will be Tindie. Tindie is Supplyframe’s (Hackaday’s parent company) answer to the question, ‘where should I sell my hardware product’. Think of it as ‘Etsy for electronics’, but with less furniture made out of pallet wood, but paradoxically more products that require a California prop 65 warning. Isn’t electronics fun?

Here’s How To Take Part:

join-hack-chatOur Hack Chats are live community events on the Hackaday.io Hack Chat group messaging. This Hack Chat will take place at noon Pacific time on Friday, July 21st. Confused about where and when ‘noon’ is? Here’s a time and date converter!

Log into Hackaday.io, visit that page, and look for the ‘Join this Project’ Button. Once you’re part of the project, the button will change to ‘Team Messaging’, which takes you directly to the Hack Chat.

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

Trackpad with Arduino PS/2-to-USB converter

Raspberry Pi Trackpad From Salvaged Trackpad Plus Arduino

July 19, 2017 by 39 Comments

Old laptops are easy to find and many have a trackpad with a PS/2 interface hardwired into the guts of the laptop. [Build It] wanted one of those trackpads for use in the DIY Raspberry Pi laptop he’s working on. But the Raspberry Pi has no PS/2 input, and he read that a PS/2 to USB adapter wouldn’t be reliable enough. His solution? Wire the trackpad to an Arduino and have the Arduino convert the trackpad’s PS/2 to USB.

After removing a few screws, he had the trackpad free of the laptop. Looking up the trackpad’s part number online he found the solder pads for data, clock and five volts. He soldered his own wires to them, as well as to the trackpad’s ground plane, and from there to his Arduino Pro Micro. After installing the Arduino PS/2 mouse and the Mouse and Keyboard libraries he wrote some code (see his Instructables page). The finishing touch was to use generous helpings of hot glue to secure all the wires, as well as the Arduino, to the back to the trackpad. By plugging a USB cable into the Arduino, he now had a trackpad that could plug in anywhere as a USB trackpad. Watch [Build It] put it all together step-by-step in the video below.

Continue reading “Raspberry Pi Trackpad From Salvaged Trackpad Plus Arduino” →

Paul Horowitz And The Search For Extra Terrestrial Intelligence

July 19, 2017 by 91 Comments

I recently had the opportunity to attend a lecture by Harvard Professor Paul Horowitz. It’s a name you likely recognize. He is best known for his iconic book the Art of Electronics which is often referred to not by its name but by the last names of the authors: “Horowitz and Hill”.

Beyond that, what do you know about Paul Horowitz? Paul is an electrical engineer and physicist and Paul has spent much of his storied career learning and practicing electronics for the purpose of finding intelligent extra terrestrial life.

Continue reading “Paul Horowitz And The Search For Extra Terrestrial Intelligence” →

This Isn’t The R2-D2 Controller You’re Looking For

July 19, 2017 by 7 Comments

Who loves a good R2-D2 robot? Everyone, but especially young Star Wars fans who — frustratingly — have no problem spotting a controller and spoiling the illusion of an R2 unit brought to life. [Bithead942]’s concealed his R2-D2’s remote and re-establishes the illusion of an autonomous droid — no Jedi mind-tricks necessary.

[Bithead942] prefers to accompany his droid in traditional a Rebel Alliance pilot’s suit, so that gives him a bit of extra space under the jumpsuit to help conceal the controller. Dismantling a Frsky Taranis X9D controller, [Bithead942] meditated on how to use it while so concealed. In a stroke of insight, he thought of his unused Wiimote nunchucks, and launched into the build.

Continue reading “This Isn’t The R2-D2 Controller You’re Looking For” →

I Am An Iconoscope

July 19, 2017 by 26 Comments

We’d never seen an iconoscope before. And that’s reason enough to watch the quirky Japanese, first-person video of a retired broadcast engineer’s loving restoration. (Embedded below.)

Quick iconoscope primer. It was the first video camera tube, invented in the mid-20s, and used from the mid-30s to mid-40s. It worked by charging up a plate with an array of photo-sensitive capacitors, taking an exposure by allowing the capacitors to discharge according to the light hitting them, and then reading out the values with another electron scanning beam.

The video chronicles [Ozaki Yoshio]’s epic rebuild in what looks like the most amazingly well-equipped basement lab we’ve ever seen. As mentioned above, it’s quirky: the iconoscope tube itself is doing the narrating, and “my father” is [Ozaki-san], and “my brother” is another tube — that [Ozaki] found wrapped up in paper in a hibachi grill! But you don’t even have to speak Japanese to enjoy the frame build and calibration of what is probably the only working iconoscope camera in existence. You’re literally watching an old master at work, and it shows.

Continue reading “I Am An Iconoscope” →

Almost An Amiga For Not A Lot

July 18, 2017 by 36 Comments

If you ask someone old enough to have been a computer user in the 16-bit era what machine they had, you’ll receive a variety of answers mentioning Commodore, Atari, Apple, or even PC brands. If your informant lay in the Commodore camp though, you’ll probably have an impassioned tale about their Amiga, its capabilities, and how it was a clearly superior platform whose potential was wasted. The Amiga was for a while one of the most capable commonly available computers, and became something of a cult within its own lifetime despite the truly dismal performance of the various companies that owned it. Today it retains one of the most active retro computer scenes, has an active software community, and even sees new hardware appearing.

For Amiga enthusiasts without the eye-watering sums required to secure one of the new Amiga-compatible machines with a PowerPC or similar at its heart, the only option to relive the glory beside finding an original machine is to run an emulator. [Marco Chiapetta] takes us through this process using a Raspberry Pi, and produces an Amiga that’s close enough to the real thing to satisfy most misty-eyed enthusiasts.

He starts with a cutesy Amiga-themed Raspberry Pi case that while it’s not essential for the build, makes an entirely appropriate statement about his new machine, We’re taken through the set-up of the Amibian emulator distro, then locating a set of Amiga ROMs. Fortunately that last step is easier than you might think, even without trawling for an illicit copy.

The result is an Amiga. OK, it’s not an Amiga, but without the classic Commodore logo is it any more not an Amiga than some of the other non-branded Amiga-compatible boards out there? Less talking, more classic gaming!

We’ve covered quite a few Amigas on these pages. Getting an A500 online was the subject of a recent post, and we brought you news of a new graphics card for the big-box Amiga’s Zorro slot.