The open source Scanning Tunnelling Microscope

Sacha De’Angeli of ChemHacker has posted an update on his open source Scanning Tunnelling Microscope project, which aims to create an Arduino-controlled high-resolution non-optical microscope licensed entirely under the GPLv3.

“I’m nearly done with a complete redesign of the digital and analog electronics, now at version 0.3,” De’Angeli writes on the ChemHacker site. “The new electronics incorporates nearly complete digital control of the STM. I’m working on ways to further increase the control the microchip has over the STM to include gain control of the many op-amps.”

The aim of the project is to design a scanning tunnelling microscope: a high-resolution non-optical device which uses electric current to produce images as detailed as those of individual atoms.

A commercial STM is well out of the reach of your average hacker, costing many thousands of pounds, but De’Angeli hopes to eventually sell his open source creation in kit form as well as providing full details for hackers to build their own implementations via the GNU General Public Licence.

A video of the ChemHackerSTM v0.1 is reproduced below, but De’Angeli warns that it’s not representative of where the project is today and is a “a poor implementation of a good analogue design with a microcontroller slapped to the inputs.

“I’ve since learned that analogue is weird compared to digital,” De’Angeli admits, “and getting those two worlds to talk properly involves a lot more finesse and art than science and equations.”

If you want to be alerted when kits are available, there’s a sign-up sheet here.

The RHT03 digital temperature and humidity sensor

RHT03 Digital Temperature and Humidity Sensor
RHT03 Digital Temperature and Humidity Sensor
Accurate but expensive - the RHT03.

While the use of analogue sensors for detecting temperature are common in the world of open source electronics, digital devices are less so. The RHT03 could help change that, offering a low-cost high-accuracy sensor which connects easily to most prototyping platforms.

The first thing to notice about the RHT03 – also known as the DHT-22 – is its breadboard-friendly layout. Mimicking a T-style package, the legs are properly spaced for connection to any common breadboard type, while also allowing for the component to be soldered to a through-hole PCB for a more permanent project.

Sadly, the RHT03 is clearly made on a budget: the legs are extremely thin, and it can be fiddly to get the breadboard to accept the component without bending one or all. If you’re using the RHT03 in a project where it’s going to be frequently moved around, consider adding some reinforcement.

The RHT03 is an odd beast: although digital, it’s not a One-Wire device and doesn’t work with any common libraries. Thankfully, resourceful hackers have fixed that problem: a GitHub project page provides a simple library for the component plus sample code which spits out the current temperature and humidity.

There are limitations, however: query the RHT03 too quickly and it will return an error, something which is never a problem with an analogue sensor. That restriction – due to the digital nature of the device – comes with an corresponding upside: unlike a thermistor, there’s no complex calculation to carry out in order to arrive at a human-readable figure.

Connecting the RHT03 to an Arduino and running the sample script results in two figures: temperature in Celsius and humidity as a percentage. Using a calibrated multimeter with K-type temperature probe proved that the temperature was accurate, and the humidity didn’t seem far off. Accuracy is official stated as ±0.5°C and ±2% RH.

Compared to using two separate components, the RHT03 has a dual advantage: the sensors are located together for better accuracy, and it requires only a single input pin on your controller along with VIN and ground connections. It’s also battery-friendly, drawing around 1.5mA when reading and 50µA when in standby mode.

If you’re using a non-Arduino prototyping platform, the RHT03 will likely still work – thanks largely to a wide supply voltage range of 3.3-6V – but you may find yourself doing a bit of hacking in order to implement the DHT22 communications library.

There is a catch in all this, however: at £8.51, the RHT03 is an extremely expensive option compared to analogue sensors. If you need accuracy, it’s a good option, but be prepared to pay for the privilege.

Pro: Accurate temperature and humidity readings from a single pin.
Con: Very expensive compared to analogue equivalents.
Supplier: Proto-Pic, £8.51
Score: 6/9

The Arduino ProtoShield v5

ProtoShield v5 Clone
The breadboard fits perfectly on the ProtoShield.

Arduino ‘shields’ – add-on boards that connect to the Arduino’s headers to add additional capabilities – are handy things, but sometimes you need something a little more custom. Although it’s possible to make your own, the Arduino’s famously non-standard pin spacing makes it difficult, but there’s a solution: the ProtoShield.

As its name suggests, the ProtoShield is a shield which makes prototyping on an Arduino significantly easier. Often supplied in kit form, the ProtoShield’s design is open source. As a result, it’s possible to get the device pre-made from a variety of sources, which sadly means you’re often taking a gamble on quality unless you buy directly from a reputable supplier.

The shield on test, unfortunately, is from no such source: manufactured by an unknown Chinese OEM and sold through Hong Kong gadget site DealExtreme, the design is based directly on Adafruit’s implementation of the ProtoShield with the logo removed before the PCB has been printed. That’s in direct contravention of the Creative Commons licence under which the open source design is provided, and we’d recommend you look elsewhere if you’re planning on buying one.

The shield itself arrives as two separate components: the ProtoShield, plus a mini-breadboard with an adhesive pad on the underside. This breadboard is specifically designed to fit on top of the ProtoShield, allowing you – if you so choose – to combine the two into a portable prototyping platform.

The other option is to use the mini-breadboard on another project, and concentrate on the ProtoShield itself. The PCB is covered in through-hole soldering points, and a glance at the underside reveals a combination of connected and disconnected circuit paths. There’s room for a wireless module, an SOIC solder pad, and in addition to the usual Arduino headers there’s an additional five for ground and 5V on many designs.

The concept is simple: prototype the layout of your custom shield’s components with the breadboard, and when you’re ready solder the components in place directly onto the shield to create a permanent custom creation. It’s a neat idea, but there’s a problem: the ProtoShield isn’t cheap. Even as an unlicensed knock-off shipped from China, the ProtoShield will set you back around £7, which compares poorly with some stripboard and a set of angled headers.

As a prototyping platform using the stick-on breadboard, however, the ProtoShield is great. If your project calls for LEDs, you’ll be pleased to see two already form part of the shield’s design, along with a handy switch. The fact that the reset switch is brought to the top is also a welcome sight, as many shields forget how inaccessible the Arduino’s version can be when the shield is in place.

Pro: It’s a great portable prototyping platform when combined with the breadboard.
Con: While easy, it’s an expensive way to make your own shields.
Supplier: DealExtreme (uncredited clone of Lady Ada’s ProtoShield)
Score: 7/9

Building stripboard prototyping modules

Robotics enthusiast and Arduino hacker June Jones has posted a guide to creating a infrared sensor module for a line-following robot which also serves as a handy guide to building homebrew sensor modules for any prototyping system.

While the guide, published over on Instructables, starts off with the familiar sight of a breadboard and an Arduino, once the initial prototyping is complete Jones demonstrates how to turn a breadboarded design into a tiny module using stripboard.

Although not as impressive as a professionally etched PCB, stripboard is handy stuff: Jones shows the design shrinking from a hefty breadboard down to a tiny module which can be plugged in to any Arduino-like prototyping system with ease.

If you’ve ever wondered how to take a breadboard concept to the next level, you could do a lot worse than follow the guide – even if Jones does admit that the stripboarded version stopped working after a short while due to a component fault.

Arduino code sharing site Sketch Garden enters beta


US Arduino specialist Wicked Devices has announced the impending launch of a site dedicated to storing code for Arduino-compatible devices.

Dubbed ‘Sketch Garden,’ the site – which is currently in a pre-launch beta phase – aims to become a central repository of Arduino Sketches, allowing users to store code snippets, libraries and completed projects for access from any Internet-connected device.

Although not yet formally launched, the site’s creators promise to open the service to the public within the next three weeks, while those unable to wait that long can request entry to the private beta programme here.

Hacker turns an Arduino into an oscilloscope

SourceForge user OLeuthold has been hard at work creating an oscilloscope-like device from something many hackers are likely to have lying around: an Arduino Uno.

The lxardoscope project creates a pleasingly oscilloscope-like display on a Linux host system to which the Arduino Uno board is connected. With a resolution of around 3,000 samples per second, the open source project won’t replace a real oscilloscope but is noteworthy for the sheer hackiness involved.

To get a clean signal, OLeuthold explains that users need to remove the ATMega chip from the Arduino Uno board post-programming and insert it into a custom-built circuit which includes a power source with ground set to -2.5V and VCC set to +2.5V.

While it’s a clever hack, some users are questioning the viability of the project as a tool. Comments on a Hack a Day post where lxardoscope was discussed range from incredulity at the poor bandwidth of the psuedo-oscilloscope to unfavourable comparisons to the rather more polished Xprotolab project.

If the naysayers haven’t put you off, the SourceForge project page has full construction details and source code.

The Nanode breaks the 1K barrier


Ken Boak, of London Hackspace, has announced that his Arduino-compatible Nanode kit has just passed the 1,000 units sold mark. While that’s not quite at the level of the official Arduinos, it’s certainly not bad going for what started off as a small-scale hackerspace project.

The Nanode is provided as a kit, featuring an ATMega328P with Arduino bootloader and pin-compatibility with existing Arduino shields. Where it differs from the standard design is in the inclusion of an integrated Ethernet connection and a set of screw terminals for a local serial bus, designed to allow users to chain together multiple Nanodes into a local sensor network.

More information on the Nanode project can be found over on the official site.

Arduino Due – ARM meets Arduino

Arduino Due board

The Arduino team had a surprise announcement to make at this year’s Maker Faire: a new design called the Due, which makes the move from eight-bit ATMega chips to a 32-bit ARM-based processor for the first time in an officially licensed product.

Arduino Due boardThe Arduino Due is designed for those who find even the Arduino Mega a little restrictive. Despite retaining pin-compatibility with its predecessors – including the irritating pin spacing that precludes the use of Veroboard and the like without offset stacking headers – it packs in a wealth of new features including:

  • 96MHz 32-bit ATMEL SAM3U Cortex-M3 CPU
  • 256KB of flash memory
  • 50KB of SRAM
  • Five SPI buses
  • Two I2C interfaces
  • Five UARTs
  • 16 analogue inputs with 12-bit resolution
  • 52 digital inputs/outputs

Unfortunately, the Due isn’t available to buy just yet. The Arduino team is running the board through an invite-only beta process, after which pre-release ‘Developer Edition’ boards will be available to buy for those who want a say in the final release.

There’s no word on pricing yet, but as soon as we have our hands on one we’ll be sure to bring you a full review.