Simple, Cheap Nitrate Tester is Open Source

Too much of a good thing can be a bad thing, and nitrate pollution due to agricultural fertilizer runoff is a major problem for both lakes and coastal waters. Assessing nitrate levels commercially is an expensive process that uses proprietary instruments and toxic reagents such as cadmium. But [Joshua Pearce] has recently developed an open-source photometer for nitrate field measurement that uses an enzyme from spinach and costs a mere $65USD to build.

The device itself is incredibly simple – a 3D printed enclosure houses an LED light source and a light sensor. The sample to be tested is mixed with a commercially available reagent kit based on the enzyme nitrate reductase, resulting in a characteristic color change proportional to the amount of nitrate present. The instrument reads the amount of light absorbed by the sample, and communicates the results to an Android device over a Bluetooth link.

Open-source instruments like this can really open up educational opportunities for STEM groups to get out into the real world and start making measurements that can make a difference. Not only can this enable citizen scientists and activists, but it also opens the door for getting farmers involved in controlling nitrate pollution at its source – knowing when a field has been fertilized enough can save a farmer unnecessary expense and reduce nitrate runoff.

There are a lot of other ways to put an open-source instrument like this to use in biohacking – photometery is a very common measuring modality in the life sciences, after all. We’ve seen similar instruments before, like a DIY spectrophotometer, or this 2015 Hackaday Prize entry medical tricorder with a built-in spectrophotometer. Still, for simplicity of build and potential impact, it’s hard to beat this instrument.

NES Reborn as Nexus Player and NES

Anyone who has a Raspberry Pi and an old Nintendo has had the same thought. “Maybe I could shove the Pi in here?” This ran through [Adam’s] head, but instead of doing the same old Raspberry Pi build he decided to put a Nexus Player inside of this old video game console, with great success. Not only does it bring the power of a modern media player, it still works as an NES.

If you haven’t seen the Nexus Player yet, it’s Google’s venture into the low-cost home media center craze. It has some of the same features of the original Chromecast, but runs Android and is generally much more powerful. Knowing this, [Adam] realized it would surpass the capabilities of the Pi and would even be able to run NES emulators.

[Adam] went a little beyond a simple case mod. He used a custom PCB and an Arduino Pro Micro to interface the original controllers to the Nexus Player. 3D printed brackets make sure everything fits inside the NES case perfectly, rather than using zip ties and hot glue. He then details how to install all of the peripherals and how to set up the Player to run your favorite game ROMs. The end result is exceptionally professional, and brings to mind some other classic case mods we’ve seen before.

Android-based Reflow Brings Solder Profiles to Your Lab

[Andy Brown] is a prolific hacker and ends up building a lot of hardware. About a year back, he built a reflow oven controller. The board he designed used a large number of surface mount parts. This made it seem like a chicken or egg first problem. So he designed a new, easy to build, Android based reflow controller. The new version uses just one, easy to solder surface mount part. By putting in a cheap bluetooth module on the controller, he was able to write an app which could control the oven using any bluetooth enabled Android phone or tablet.

The single PCB is divided into the high voltage, mains powered section separated from the low power control electronics with cutout slots to take care of creepage issues. A BTA312-600B triac is used to switch the oven (load) on and off. The triac is controlled by a MOC3020M optically isolated triac driver, which in turn is driven by a micro controller via a transistor. The beefy 12Amp T0220 package triac is expected to get hot when switching the 1300W load, and [Andy] works through the math to show how he arrived at the heat sink selection. To ensure safety, he uses an isolated, fully encased step down transformer to provide power to the low voltage, control section. One of his requirements was to detect the zero cross over of the mains waveform. Using this signal allows him to turn on the triac for specific angle which can be varied by the micro controller depending on how much current the load requires. The rectified, but unfiltered ac signal is fed to the base of a transistor, which switches every time its base-emitter voltage threshold is reached.

For temperature measurement, [Andy] was using a type-k thermocouple and a Maxim MAX31855 thermocouple to digital converter. This part caused him quite some grief due to a bad production batch, and he found that out via the eevblog forum – eventually sorted out by ordering a replacement. Bluetooth functions are handled by the popular, and cheap, HC-06 module, which allows easy, automatic pairing. He prototyped the code on an ATmega328P, and then transferred it to an ATmega8 after optimising and whittling it down to under 7.5kb using the gcc optimiser. In order to make the board stand-alone, he also added a header for a cheap, Nokia 5110 display and a rotary encoder selector with switch. This allows local control without requiring an Android device.

Gerbers (zip file) for the board are available from his blog, and the ATmega code and Android app from his Github repo. The BoM list on his blog makes it easy to order out all the parts. In the hour long video after the break, [Andy] walks you through solder tip selection, tips for soldering SMD parts, the whole assembly process for the board and a demo. He then wraps it up by connecting the board to his oven, and showing it in action. He still needs to polish his PID tuning and algorithm, so add in your tips in the comments below.

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Hackaday Retro Edition: Androids And Amigas

Tiny ARM boards are everywhere, and if the Raspberry Pi is any indication, they’re mostly used for emulating old consoles and computers. With only a $30 single board computer, it’s easy to emulate an SNES, Apple II, C64, or any of the other piece of classic 80s or 90s hardware.

Understandably, there will eventually be a few projects and products that hope to capitalize on this retro trend. Few of them will go through the rigamarole of actually licensing the relevant IP. The Armiga is one of these projects. It’s an emulated Amiga 500 with 1MB of RAM packaged in what looks like a 3.5″ external floppy drive.

Inside this tiny little box is a dual core ARM for Amiga emulation. For the most part, this is just a basic Android system, but the real selling point of this system is the Armiga Project software. This is a full emulator and game browser that also includes a legal (!) copy of Kickstart 1.3. The ‘upscale’ version of the Armiga also includes a floppy disk controller and drive, should you ever want to dump all those old floppies sitting around in your attic.

This isn’t the first time we’ve heard about the Armiga. It was a crowdfunding campaign a year ago that was unsuccessful for reasons we can’t comprehend. The creators of the Armiga have forged on, and now these tiny little boxes of guru meditation have started shipping. The Beta units have sold out and there’s a waiting list for more.

Android Donut Running On A Graphing Calculator

[Josh] is trying to fight a misconception that Android only runs on fast, powerful smartphones. He’s convinced Android will run on extremely low-end hardware, and after a great deal of searching, hit upon a great combination. He’s running Android Donut on a TI nSpire CX graphing calculator.

Unlike just about every other TI calculator, homebrew developers are locked out of the nSpire CX and CX CAS. Without the ability to run native applications on this calculator, [Josh] would be locked out of his platform of choice without the work of the TI calculator community and Ndless, the SDK for this series of calculators.

With the right development environment, [Josh] managed to get the full Android stack up and running and ironed the bugs out. Everything he’s done is available on the GitHub for this project, and with the instructions on the xda developers post, anyone can get a version of Android running on this TI calculator.

While [Josh] has Android Donut running along with most of the 1.6 apps, a terminal emulator, keyboard, WiFi, USB, and Bluetooth running, this calculator-come-Android isn’t as useful as you think it would be. The vast majority of calculator emulators on the Google Play store require Android version 2.2 and up. Yes, [Josh] can still run a TI-83 emulator on his calculator, but finding an app that’s compatible with his version of Android is a challenge.

Still, even with a 150MHz processor and 64MB of RAM – far less than what was found in phones that shipped with Donut – [Josh] is still getting surprisingly good performance out of his calculator. He can play some 2D games on it, and the ability to browse the web with a calculator is interesting, to say the least. It is, however, the perfect example that you don’t need the latest and greatest phone to run Android. Sometimes you don’t even need a phone.

Hacking An Android Laptop To Run Linux

A few years ago, someone at Lenovo realized they could take an Android tablet, add a keyboard, and sell a cheap netbook that’s slightly more useful than a YouTube and Facebook machine. Since then, Lenovo has stopped making the A10 notebook and has moved on to manufacturing Chromebooks. That doesn’t mean this little Laptop doesn’t have some life left in it: it still has a Cortex A9 Quad core CPU, is reasonably priced on the ‘defective’ market, and can now run a full-blown Linux.

When the A10 notebook was released, there was a statement going around saying it was impossible to install Linux on it. For [Steffen] that was a challenge. He cracked open this netbook and took a look around the Flash chips. There were two tiny pads that could be shorted to put the device in recovery mode, and the entire thing can be booted from a USB stick.

[Steffen] ran into a problem while putting a new kernel on the netbook: there was a null pointer reference in some device during boot. The usual way of diagnosing this problem is to look at the console to see what device failed. This netbook doesn’t have a UART, though, and [Steffen] had to use an FTDI chip and set the console to USB to see why this device failed.

Just about everything on this tiny laptop works right now, with a few problems with WiFi, webcam, and standby mode – all normal stuff for a putting Linux on a random machine. It’s worth it, though: the quad-core ARM is a very good chip, and [Steffen] is running x86 apps with qemu. Not bad for something that can be found very, very cheap.

On Your Phone While Driving an Electric Skateboard

Skateboards are fun, but you have to do all that pesky kicking in order to get anywhere. That’s why [Nick] decided to build his own electric skateboard. Not only is the skateboard powered with an electric motor, but the whole thing can be controlled from a smart phone.

[Nick] started out with a long board deck that he had made years ago. After cleaning it up and re-finishing it, the board was ready for some wheels. [Nick] used a kit he found online that came with the trucks, wheels, and a belt. The trucks have a motor mount welded in place already. [Nick] used a Turnigy SK3 192KV electric motor to drive the wheels. He also used a Turnigy electronic speed controller to make sure he could vary the speed of the board while riding.

Next [Nick] needed some interface between a smart phone and the motor controller. He chose to use an Arduino Nano hooked up to a Bluetooth module. The Nano was able to directly drive the motor controller, and the Bluetooth module made it easy to sync up to a mobile phone. The Android app was written using MIT’s App Inventor software. It allows for basic control over the motor speed so you can cruise in style. Check out the video below for a slide show and some demonstration clips.

It’s a popular project, and eerily similar to the one we saw a couple months back.

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