Just about everywhere you go, there’s a reed switch nearby that’s quietly going about its work. Reed switches are so ubiquitous that you’re probably never more than a few feet away from one at any given time, especially at home or in the car. You might have them on your doors and windows as part of a burglar alarm system. They keep your washing machine from running when the lid is open, and they put your laptop to sleep when you close the lid. They know if the car has enough brake fluid and whether or not your seat belt is fastened.
Reed switches are interesting devices with a ton of domestic and industrial applications. We call them switches, but they’re also sensors. In fact, they only do the work of a switch while they can sense a magnetic field. They are capable of switching AC or DC at low and high voltages, but they don’t need electricity to work. Since they’re sealed in glass, they are impervious to dirt, dust, corrosion, temperature swings, and explosive environments. They’re cheap, they’re durable, and in low-current applications they can last for about a billion actuations.
Continue reading “Mechanisms: The Reed Switch”
If your hobby is chasing radiosondes across vast stretches of open country, and if you get good enough at it, you’ll eventually end up with a collection of the telemetry packages that once went up on weather balloons to record the conditions aloft. Once you’ve torn one or two down though, the novelty must wear off, which is where this radiosonde conversion to an active L-band antenna comes from.
As it happens, we recently discussed the details of radiosondes, so if you need a primer on these devices, check that out. But as Australian ham [Mark (VK5QI)] explains, radiosondes are a suite of weather instruments crammed into a lightweight package with a GPS receiver and a small transmitter. Lofted beneath a weather balloon into the stratosphere, a radiosonde transmits a wealth of data back to the ground before returning on a parachute after the balloon bursts. [Mark] had his eyes on the nice quadrifilar helical antenna used by the Vaisla R92 radiosonde’s GPS receiver, with the aim of repurposing them. He had a lot of components to remove while still retaining the low-noise amplifier (LNA), but in the end managed to get a working antenna with 40 dB gain in the L-band, and with the help of an RTL-SDR dongle he picked up solid signals from Iridium satellites.
Want to score your own radiosonde to play with? First, you have to know how to listen in so you can find them. Or, you know – there’s always eBay.
[Andy Osusky]’s project submission for the Hackaday Prize is to build an autonomous sailboat to cross the Atlantic Ocean. [Andy]’s boat will conform to the Microtransat Challenge – a transatlantic race for autonomous boats. In order to stick to the rules of the challenge, [Andy]’s boat can only have a maximum length of 2.5 meters, and it has to hit the target point across the ocean within 25 kilometers.
The main framework of the boat is built from aluminum on top of a surfboard, with a heavy keel to keep it balanced. Because of the lightweight construction, the boat can’t sink and the heavy keel will return it upright if it flips over. The sail is made from ripstop nylon reinforced by nylon webbing and thick carbon fiber tubes, in order to resist the high ocean winds.
The electronics are separated into three parts. A securely sealed Pelican case contains the LiFePo4 batteries, the solar charge controller, and the Arduino-based navigation controller. The communications hardware is kept in polycarbonate cases for better reception. One case contains an Iridium satellite tracker, compass, and GPS, the other contains two Globalstar trackers. The Iridium module allows the boat to transmit data via the Iridium Short Burst Data service. This way, data such as GPS position, wind speed, and compass direction can be transmitted.
[Andy]’s boat was launched in September from Newfoundland headed towards Ireland. However, things quickly seemed to go awry. Storms and crashes caused errors and the solar chargers seemed not to be charging the batteries. The test ended up lasting about 24 days, during which the boat went almost 1000km.
[Andy] is redesigning the boat, changing to a rigid sail and enclosing the hardware inside the boat. In the meantime, the project is open source, so the hardware is described and software is available on GitHub. Be sure to check out the OpenTransat website, where you can see the data from the first sailing. Also, check out this article on autonomous kayaks, and this one about a swarm of autonomous boats.
Continue reading “Autonomous Transatlantic Seafaring”
Put a message in a bottle and toss it in the ocean, and if you’re very lucky, years later you might get a response. Drop a floating Arduino-fied buoy into the ocean and if you’ve engineered it well, it may send data back to you for even longer.
At least that’s what [Wayne] has learned since his MDBuoyProject went live with the launching of a DIY drift buoy last year. The BOM for the buoy reads like a page from the Adafruit website: Arduino Trinket, an RTC, GPS module, Iridium satellite modem, sensors, and a solar panel. Everything lives in a clear plastic dry box along with a can of desiccant and a LiPo battery.
The solar panel has a view through the case lid, and the buoy is kept upright by a long PVC boom on the bottom of the case. Two versions have been built and launched so far; alas, the Pacific buoy was lost shortly after it was launched. But the Atlantic buoy picked up the Gulf Stream and has been drifting slowly toward Europe since last summer, sending back telemetry. A future version aims to incorporate an Automatic Identification System (AIS) receiver, presumably to report the signals of AIS transponders on nearby ships as they pass.
We like the attention to detail as well as the low cost of this build. It’s a project that’s well within reach of a STEM program, akin to the many high-altitude DIY balloon projects we’ve featured before.
Continue reading “Low-cost Drift Buoy Plies the Atlantic for Nearly a Year”
High-altitude ballooning is becoming a popular activity for many universities, schools and hacker spaces. The balloons, which can climb up to 40 km in the stratosphere, usually have recovery parachutes to help get the payload, with its precious data, back to solid ground safely. But when you live in areas where the balloon is likely to be flying over the sea most of the time, recovery of the payload becomes tricky business. [Paul Clark] and his team from Durham University’s Centre for Advanced Instrumentation are working on building a small, autonomous glider – essentially a flying hard drive – to navigate from 30 km up in the stratosphere to a drop zone somewhere near a major road. An important element of such a system is the locator beacon to help find it. They have now shared their design for an “Iridium 9603 Beacon” — a small Arduino-compatible unit which can transmit its location and other data from anywhere via the Iridium satellite network.
The beacon uses the Short Burst Data service which sends email to a designated mail box with its date, time, location, altitude, speed, heading, temperature, pressure and battery voltage. To do all of this, it incorporates a SAMD21G18 M0 processor; FGPMMOPA6H GPS module; MPL3115A2 altitude sensor; Iridium 9603 Short Burst Data module + antenna and an LTC3225 supercapacitor charger. Including the batteries and antenna, the whole thing weighs in at 72.6 g, making it perfectly suited for high altitude ballooning. The whole package is powered by three ‘AAA’ Energizer Ultimate Lithium batteries which ought to be able to withstand the -56° C encountered during the flight. The supercapacitors are required to provide the high current needed when the beacon transmits data.
The team have tested individual components up to 35 km on a balloon flight from NASA’s Columbia Scientific Balloon Facility and the first production unit will be flown on a much smaller balloon, launched from the UK around Christmas. The GitHub repository contains detailed information about the project along with the EagleCAD hardware files and the Arduino code. Now, if only Santa carried this on his Sleigh, it would be easy for NORAD to track his progress in real time.
We live in a connected world, but that world ends not far beyond the outermost cell phone tower. [John Grant] wants to be connected everywhere, even in regions where no mobile network is available, so he is building a solar powered, handheld satellite messenger: The MyComm – his entry for the Hackaday Prize.
The MyComm is a handheld touch-screen device, much like a smartphone, that connects to the Iridium satellite network to send and receive text messages. At the heart of his build, [John] uses a RockBLOCK Mk2 Iridium SatComm Module hooked up to a Teensy 3.1. The firmware is built upon a FreeRTOS port for proper task management. Project contributor [Jack] crafted an intuitive GUI that includes an on-screen keyboard to write, send and receive messages. A micro SD card stores all messages and contact list entries. Eventually, the system will be equipped with a solar cell, charging regulator and LiPo battery for worldwide, unconditional connectivity.
2016 will be an interesting year for the Iridium network since the first satellites for the improved (and backward-compatible) “Iridium NEXT” network are expected to launch soon. At times the 66 Iridium satellites currently covering the entire globe were considered a $5B heap of space junk due to deficiencies in reliability and security. Yet, it’s still there, with maker-friendly modems being available at $250 and pay-per-use rates of about 7 ct/kB (free downstream for SDR-Hackers). Enjoy the video of [Jack] explaining the MyComm user interface:
Continue reading “Hackaday Prize Entry: MyComm Handheld Satellite Messenger”
This is the Pinta, an autonomous sailboat built to attempt an ocean crossing from Ireland to Martinique (in the Caribbean). A group of researchers at Aberystwyth University built her as part of the Microtransat Challenge.
To keep tabs on the vessel her creators included an Iridium short burst data modem with a backup system made from a SPOT satellite tracker using a PIC microcontroller to trigger a transmission every six hours. The sailing systems are a conglomeration of a Gumstix board, GPS, a windshield wiper motor to control the sail, and a tiller pilot for steering. A set of solar panels helps to top off the lead-acid batteries that power the system.
Unfortunately the old gal has encountered problems. You can see from the tracking data that, although it sailed 500 km in the last twelve days, she is still just off the coast of Ireland. The primary tracking system has failed, which could signal a system-wide computer failure. We hope the team will eventually recover the vessel as we’re interested in finding out what caused this unfortunate turn of events.