Measuring Tire Pressure By Cutting A Hole In An Inner Tube

RFID tags are really very primitive pieces of technology. Yes, they harvest energy from an RFID reader and are able to communicate a few bits of data, but for a long time these tags have been unable to provide useful data beyond a simple ID number. [CaptMcAllister] found a new RFID sensor platform from TI and managed to make a wireless pressure sensor that fits in the inner tube of his bike.

The sensor [Capt] is using comes from TI’s RF430 series that include a few neat sensors that don’t require batteries, but are still able to communicate sensor data to a cell phone or other RFID reader. With a pressure sensor, this tiny microcontroller can receive power from an RFID reader and send it back to a phone app, all without wires.

[CaptMcAllister] cut open an inner tube for his bike, epoxied his PCB to a patch, and sealed everything back up again. After a quick test for leaks, [Capt] found the data coming from the sensor was extraordinarily accurate, and should hold up well enough to be used in his bike.

Mystery FPGA Circuit Feels the Pressure

You have an FPGA circuit and you want the user to interact with your circuit by pushing a button. Clearly, you need a button, right? Not so fast! [Clifford Wolf] recently found a mysterious effect that lets him detect when someone pushes on his iCEstick board.

The video below shows the mystery circuit (which is just the stock iCEstick board), which appears to react any time you flex the PC board. The Verilog implements a simple ring oscillator (basically an inverter with its output tied to its input).

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Hackaday Prize Semifinalist: A Mobile Node

The future is the Internet of Things, or so we’re told, and with that comes the requirement for sensors attached to the Internet that also relay GPS and location data. [Camilo]’s MobileNodes do just that. He’s designed a single device that will listen to any sensor, upload that data to the Internet over GSM or GPRS, and push all that data to the cloud.

The MobileNode is a small circular (7cm) PCB with a standard ATMega32u4 microcontroller. Attached to this PCB are GSM/GPRS and GPS/GLONASS modules to receive GPS signals and relay all that data to the cloud. To this, just about any sensor can be added, including light sensors, PIR sensors, gas and temperature sensors, and just about anything else that can be measured electronically.

Of course the biggest problem with a bunch of sensors on an Internet of Things device is pulling the data from the Internet. For that, [Camilo] designed a web interface that shows sensor data directly on a Google Map. You can check out the project video below.

The 2015 Hackaday Prize is sponsored by:

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Hackaday Prize Entry: Gas Grenade Helps Instead of Exploding

If someone lobs a grenade, it’s fair to expect that something unpleasant is going to happen. Tear gas grenades are often used by riot police to disperse an unruly crowd, and the military might use a smoke grenade as cover to advance on an armed position, or to mark a location in need of an airstrike. But some gas grenades are meant to help, not hurt, like this talking gas-sensing grenade that’s a 2015 Hackaday Prize entry.

Confined space entry is a particularly dangerous aspect of rescue work, especially in the mining industry. A cave in or other accident can trap not only people, but also dangerous gasses, endangering victims and rescuers alike. Plenty of fancy robots have been developed that can take gas sensors deep into confined spaces ahead of rescuers, but [Eric William] figured out a cheaper way to sniff the air before entering. An MQ2 combination CO, LPG and smoke sensor is interfaced to an Arduino Nano, and a 433MHz transmitter is attached to an output. A little code measures the data from the sensors and synthesizes human voice readings which are fed to the transmitter. The whole package is stuffed into a tough, easily deployed package – a Nerf dog toy! Lobbed into a confined space, the grenade begins squawking its readings out in spoken English, which can be received by any UHF handy-talkie in range. [Eric] reports in the after-break video that he’s received signals over a block away – good standoff distance for a potentially explosive situation.

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DDR-ing a Simon Game with a Raspberry Pi

Since 1998 we’ve been privileged to partake in an arcade game known as Dance Dance Revolution, but before that, way back in the 70’s, was the Simon game. It’s essentially a memory game that asks the player to remember a series of lights and sounds. [Uberdam] decided to get the best of both worlds and mixed the two together creating this giant foot controlled Simon game. (English translation.)

The wood platform that serves as the base of the project was fitted with four capacitive sensors, each one representing a “color” on the Simon game. When a player stomps on a color, a capacitive sensor sends a signal to a relay which in turn notifies the Raspberry Pi brain of the input. The Pi also takes care of showing the player the sequence of colored squares that must be stepped on, and keeps track of a player’s progress on a projector.

This is a pretty good way of showing how a small, tiny computer like the Raspberry Pi can have applications in niche environments while also being a pretty fun game. We all remember Simon as being frustrating, and we can only imagine how jumping around on a wooden box would make it even more exciting. Now, who can build a robot that can beat this version of Simon?

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Upgrading an Old Camera with a New Light Meter

[Marc] has an old Voigtländer Vito CLR film camera. The camera originally came with an analog light meter built-in. The meter consisted of a type of solar panel hooked up to a coil and a needle. As more light reached the solar panel, the coil became energized more and more, which moved the needle farther and farther. It was a simple way of doing things, but it has a down side. The photo panels stop working over time. That’s why [Marc] decided to build a custom light meter using newer technology.

[Marc] had to work within the confines of the tiny space inside of the camera. He chose to use a LM3914 bar display driver IC as the primary component. This chip can sense an input voltage against a reference voltage and then display the result by illuminating a single LED from a row of ten LEDs.

[Marc] used a photo cell from an old calculator to detect the ambient light. This acts as a current source, but he needed a voltage source. He designed a transimpedence amplifier into his circuit to convert the current into a voltage. The circuit is powered with two 3V coil cell batteries, regulated to 5V. The 5V acts as his reference voltage for the display driver. With that in mind, [Marc] had to amplify this signal further.

It didn’t end there, though. [Marc] discovered that when sampling natural light, the system worked as intended. When he sampled light from incandescent light bulbs, he did not get the expected output. This turned out to be caused by the fact that incandescent lights flicker at a rate of 50/60 Hz. His sensor was picking this up and the sinusoidal output was causing problems in his circuit. He remedied this by adding two filtering capacitors.

The whole circuit fits on a tiny PCB that slides right into position where the original light meter used to be. It’s impressive how perfectly it fits considering everything that is happening in this circuit.

[Thanks Mojay]

Disassembled Mouse Keeps Track Of Gas Meter

After building devices that can read his home’s electricity usage, [Dave] set out to build something that could measure the other energy source to his house: his gas line. Rather than tapping into the line and measuring the gas directly, his (much safer) method was to simply monitor the gas meter itself.

The major hurdle that [Dave] had to jump was dealing with an ancient meter with absolutely no modern electronics like some other meters have that make this job a little easier. The meter has “1985” stamped on it which might be the manufacturing date, but for this meter even assuming that it’s that new might be too generous. In any event, the only option was to build something that could physically watch the spinning dial. To accomplish this, [Dave] used the sensor from an optical mouse.

The sensor is surrounded by LEDs which illuminate the dial. When the dial passes a certain point, the sensor alerts an Arduino that one revolution has occurred. Once the Arduino has this information, the rest is a piece of cake. [Dave] used KiCad to design the PCB and also had access to a laser cutter for the enclosure. It’s a great piece of modern technology that helps integrate old analog technology into the modern world. This wasn’t [Dave]’s first energy monitoring system either; be sure to check out his electricity meter that we featured a few years ago.