Comfort Thermometer With Impressive LED Display

A frequent early project for someone learning to use a microcontroller such as an Arduino board involves hooking up a temperature sensor and an LCD display to make a digital thermometer. Not many components are involved, but it provides a handy practical introduction to interfacing peripherals. Once you’ve passed that step in your tech education, do you ever return to thermometers? Probably not, after all what can you add to a thermometer but a sensor and a display?

Perhaps if you have asked yourself that question you might be interested in [Richard Stevens]’s thermometer project, as he refers to it, a Comfort Thermometer Display. It takes the form of an Ikea Ribba frame inset with 517 LEDs arranged as a central set of seven segment displays, a ring of bar graphs, and an outer ring of RGB LEDs. Behind the scenes is a mass of cabling, and four shaped pieces of stripboard to fit the area around the LEDs. The display cycles through readings for temperature, heat index, and humidity.

Powering it all are a brace of microcontrollers: an ATMega328 for the 7-segments and a range of PICs controlling the bar graphs and RGB LEDs. Another PIC handles RF communication with the sensors, which are housed in a remote box. We’ve embedded the video of the device in operation below the break, and we’re sure you’ll agree it’s an impressive piece of work.

Hacking Together a Temperature Sensor for Boiling Milk

Ever have trouble justifying your hacking to anyone from another generation? [Domen] presented his mother with a custom-made device that monitors the milk temperature as it boils on the stove, preventing boil-over. And he made the device robust, simple to use, and foolproof. To his mom, it must look like he’s a wizard — able to conjure up home electronics out of solder smoke and some plywood.

Of course, we know better. Inside his gadget is a simple temperature sensor, an ATtiny841, a very nice home-made PCB, a buzzer, an LCD, and some pushbuttons. [Domen] rubbed together a few pre-existing libraries, and had a working prototype inside a nice wooden box on the quick. It’s a simple hack, but imagine how this must look to a muggle. For the detailed incantations, check out [Domen]’s GitHub for the project.

Solar-powered Weather Station Has the Complete Suite of Sensors

There was a time when getting weather conditions was only as timely or as local as the six o’clock news from the nearest big-city TV station. Monitoring the weather now is much more granular thanks to the proliferation of personal weather stations. For the ultimate in personalized weather, though, you might want to build your own solar powered weather station.

It looks like [Brian Masney] went all out in designing his weather station. It supports a full stack of sensors – wind speed and direction, rain, temperature, pressure, and dew point. About the only other parameters not supported (yet) are solar radiation, UV, and soil moisture and temperature. The design looks friendly enough that adding those sensors should be a snap – if fact, the 3D models in his GitHub repo suggest that he’s already working on soil sensors. The wind and rain sensor boom is an off-the-shelf unit from Sparkfun, and the temperature and pressure sensors are housed in a very professional 3D printed screen enclosure. All the sensors talk to a Raspberry Pi living in a (hopefully) waterproof enclosure topped with a solar panel for charging the stations batteries. All in all it’s a comprehensive build; you can check out the conditions at [Brian]’s place on Weather Underground.

Weather stations are popular around these parts, as witnessed by this reverse-engineered sensor suite or even this squirrel-logic based station.

Jump In When The Water Is Just Right With A Wireless Swimming Pool Thermometer

[David]’s family acquired a swimming pool. While it’s not his favorite activity in the world, every now and then he’ll indulge in the blue plastic bin full of water occupying previously pristine land in his backyard.

As he says, cool beer is pleasant, but cool water tends to put a damper on the experience. Rather than do something pedestrian like touch the water himself to discover its temperature; he saw an opportunity for a fun little project in a wireless temperature monitor.

The heart of the device is a Telecom Design TD1208 which runs on the French SigFox network. For a small fee any device on the network can send up to 140 12byte packets of data a day. Not a lot, but certainly acceptable for the Microchip MCP9700 temperature sensor it uses. He got the board up and running, and even made his own custom helical coil antenna.

The case was 3D printed out of PLA. It’s a tiered cylindrical bobber. The wider top section floats on the water and the base acts as a ballast, holding the battery and sensor.  The bobber is powered by a combination of  a questionable Chinese lithium battery, charging circuit, and solar panel. [Dave] was keen to point out that the battery is, technically, water cooled.

He wrapped up the code for the bobber and used SigFox’s SDK to build a nice web interface. Now, when the rare mood strikes him, he can remain inside if the conditions aren’t right for a swim.

Zero Parts-Count Temperature Sensor

Quick: What’s the forward voltage drop on a conducting diode? If you answered something like 0.6 to 0.7 V, you get a passing grade, but you’re going to have to read on. If you answered $V_F = \frac{T-T_0}{k}$ where T0 and k are device-specific constants to be determined experimentally, you get a gold Jolly Wrencher.

[Jakub] earned his Wrencher, and then some. Because not only did he use the above equation to make a temperature sensor, he did so with a diode that you might have even forgotten that you have on hand — the one inside the silicon of a MOSFET — the intrinsic body diode.

[Jakub]’s main project is an Arduino-controlled electronic load that he calls the MightWatt, and a beefy power MOSFET is used as the variable resistance element. When it’s pulling 20 or 30 A, it gets hot. How hot exactly is hard to measure without a temperature sensor, and the best possible temperature sensor would be one that was built into the MOSFET’s die itself.

There’s a bunch of detail in his write-up about how he switches the load in and out to measure the forward drop, and how he calibrates the whole thing. It’s technical, but give it a read, it’s good stuff. This is a great trick to have up your sleeve.

And if you’re in the mood for more stupid diode tricks, we recommend using them as solar cells or just stringing a bunch of them together to make a thermal camera.

Scientific research, especially in the area of robotics, often leverages cutting-edge technology. Labs filled with the latest measurement and fabrication gear are unleashed on the really tough problems, like how to simulate the exquisite sensing abilities of human skin. One lab doing work in this area has taken a different approach, though, by building multi-functional sensors arrays from paper.

A group from the King Abdullah University of Science and Technology in Saudi Arabia, led by [Muhammad M. Hussain], has published a fascinating paper that’s a tour de force of getting a lot done with nothing. Common household items, like Post-It notes, kitchen sponges, tissue paper, and tin foil, are used to form the basis of what they call “paper skin”. Fabrication techniques – scissors and tape – are ridiculously simple and accessible to anyone who made it through kindergarten.

They do turn to a Circuit Scribe pen for some of their sensors, but even this nod to high technology is well within their stated goal of making it possible for anyone to fabricate sensors at home. The paper goes into great detail about how the sensors are made, how they interact, and how they are interfaced. It’s worth a read to see what you can accomplish with scraps.

For another low-tech paper-based sensor, check out this capacitive touch sensor keyboard.

Thanks for the tip, [Mattias]

Warm Up Your Small Talk with a Thermometer Scarf

Just how cold is it out there? This giant thermometer scarf is a fantastic entry-level wearables project. It’s sure to strike up conversations that move past the topic of weather.

The scarf is built around a FLORA, a Neopixel ring that represents the bulb, and a short length of Neopixels to show the temperature in Fahrenheit and Celsius. Temperature sensing is done with a poorly documented DHT11 that gave [caitlinsdad] the fits until he found Adafruit’s library for them.To make the scarf, [caitlinsdad] used a nice cozy micro-fleece. He built a pocket for the electronics and padded it with polyester fiber fill to diffuse the LEDs. This makes the lights blur and run together, resembling a mercury thermometer.

Once it was up and running, [caitlinsdad] figured out the temperature scale based on the DHT11 readings and marked it out on the scarf with a permanent marker. [caitlinsdad] has a few mods in mind for this project. For instance, it would be easy to add haptic feedback to keep you from being exposed for too long. Another wearable in the same spirit is this hat that has a sunblock reminder system.