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I'm currently a sophomore at Worcester Polytechnic Institute studying Robotics Engineering. The third course in the series, RBE 2002, focusing on sensors. In a group of 4 students, we built a robot that could autonomously navigate a maze, locate a flame, put it out and report its X,Y, and Z position relative to its starting position. The robot was required to use an IMU and a flame sensor provided to us. All other sensors and parts are up to the group to use to complete the challenge.

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I'm currently a sophomore at Worcester Polytechnic Institute studying Robotics Engineering. The third course in the series, RBE 2002, focusing on sensors. In a group of 4 students, we built a robot that could autonomously navigate a maze, locate a flame, put it out and report its X,Y, and Z position relative to its starting position. The robot was required to use an IMU and a flame sensor provided to us. All other sensors and parts are up to the group to use to complete the challenge.

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[Pawel] has a weather station, and its nerve-center is a Raspberry Pi. He wanted to include a light sensor but the problem is, the Pi doesn’t have a built-in ADC to read the voltage off the light-dependent resistor that he (presumably) had in his junk box. You can, of course, buy I2C ADC chips and modules, but when you’ve already got a microcontroller that has ADC peripherals on board, why bother?

[Pawel] wired up a tremendously simple circuit, downloaded some I2C slave-mode code, and added an LED for good measure. It’s all up on GitHub if you’re interested.

We’re covering this because we rarely see people coding for I2C slave devices. Everyone and their mom uses I2C to connect to sensors, for which the Arduino “Wire” library or “i2c-tools” on the Pi do just fine. But what do you do when you want to make the I2C device? [Pawel]’s project makes use of TinyWireS, a slave-mode SPI and I2C library for AVR ATtiny Arduino projects.

Here, [Pawel] just wanted a light sensor. But if you’re building your own devices, the sky is the limit. What’s the most esoteric I2C sensor that you can imagine? (And is it really the case that we haven’t seen an I2C slave device hack since 2010?)

Certainly everyone remembers passing time in a boring high school class playing games on a graphing calculator. Whether it was a Mario-esque game, Tetris, or BlockDude, there are plenty of games out there for pretty much all of the graphing calculators that exist. [Christopher], [Tim], and their colleagues from Cemetech took their calculator game a little bit farther than we did, and built something that’ll almost surely disrupt whatever class you’re attempting to pay attention in: They built a graphing calculator whac-a-mole game.

This game isn’t the standard whac-a-mole game, though, and it isn’t played on the calculator’s screen. Instead of phyiscal “moles” the game uses LEDs and light sensors enclosed in a box to emulate the function of the moles. In order to whack a mole, the player only needs to interrupt the light beam which can be done with any physical object. The team made extensive use of the ArTICL library which allows graphing calculators to interface with microcontrollers like the MSP432 that they used, and drove the whole thing with a classic TI-84.

This project is a fun way to show what can be done with a graphing calculator and embedded electronics, and it was a big hit at this past year’s World Maker Faire. Calculators are versatile in other ways as well. We’ve seen them built with open hardware and free software, And we’ve even seen them get their own Wi-Fi.

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Laser tripwire security systems can be expensive propositions that don't always work as planned -- just ask Raytheon, which saw its $100 million Perimeter Intrusion Detection System for JFK International Airport undermined by one wayward jet skier. Taking that as a form of dare, Justin Huynh and teammates at Liquidware have devised a much cheaper (if also much smaller) tripwire of their own. Any interruption of a laser pointer's beam is caught by an Arduino light sensor that promptly sends the alert to an Android-running BeagleBoard xM; if a toy like Bruce the shark dares cross the line, the BeagleBoard sends a Twitter message to let the authorities, or at least Huynh, clamp down on the trespasser. The invention won't replace Raytheon's handiwork anytime soon, although Huynh notes that additional or more powerful sensors could theoretically catch real, muscle-bound sharks and not just their plastic counterparts. The supply checklist and source code are waiting on the company's project page below, so those who'd like to ward off miniature invasions can get started today.

Continue reading Liquidware team crafts laser tripwire that tweets intruder alerts, keeps fake sharks at bay (video)

Filed under: Misc. Gadgets

Liquidware team crafts laser tripwire that tweets intruder alerts, keeps fake sharks at bay (video) originally appeared on Engadget on Mon, 20 Aug 2012 19:17:00 EST. Please see our terms for use of feeds.

If you connect led in the opposit way he can act as light sensor:

positive leg to analog pin

negative leg to 5V

You can use that for some things, but he not sensetive as LDR,

ןf you use a for example a green led he not "see" well red light

If you use charlieplexing method you can control one led to light and as a light sensor.

The idea is like this:

Two wires connect the led to two analog pins.

To light the led you set the two analog pins as digital output and one high one low. 

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