Blackboard digitization for under $40

Digital White/Black Boards or “Smart Boards” are very useful in modern classrooms, but their high cost often makes it difficult to convince administrators from loosening their purse strings. Cooper Union’s 2nd annual HackCooper event in New York wanted students to design and build hardware and software projects that both solve real problems and spark the imagination. At the 24 hour hackathon, the team of [harrison], [david] and [caleb] decided to put together a low-cost and simple solution to digitizing classroom black board content.

A chalk-holder is attached to two strings, each connected over a pulley to a weight. The weights slide inside PVC pipes at the two sides of the black board. Ultrasonic sensors at the bottom of each tube measure the distance to the weights. The weights sit in static equilibrium, so they serve the purpose of keeping the string taut without negatively interfering with the writer.

With a couple of calibration points to measure the extent of displacement of each weight, board width can be determined, making it easy to adapt to different sizes of boards. Once calibrated, the system can determine position of the chalk over the board based on some trigonometrical calculations. Since they had just 24 hours to hack the system together, they had to use a hand operated radio with a couple of buttons to provide user control. Pressing the “Write” button starts transmitting chalk movements to the digital screen. A second button on the radio remote serves to “Erase” the digital screen. After receiving the chalk position data, they had to do a fair amount of processing to eliminate noise and smooth out the writing on the digital screen.

A server allows the whole class to receive the chalk board data in real time. After each “Erase” command, the chalk board state is saved and logged on the server, thus allowing previous content to be viewed or downloaded. If only text is written, optical character recognition can be used to further digitize the content.

What makes the project really useful is the low cost. The sensors cost a dollar. The other parts – PVC pipe, weights/pulleys, Arduino and the Radio key fob – were all bought for under 40 dollars. For some additional cost (and maybe more time in their case) they could have automated the detection of when the chalk was actually doing the writing. The team have made their code available on Github. For a Chalk board at the other end of the cost spectrum, check this one out. Video below.

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Lamp Comes to Life with Ultrasonic Sensors

Fans of the bouncing lamp from the Pixar corporate logo will enjoy [Daniel]’s latest project. It’s a motion controlled desk lamp that uses ultrasonic sensors to control its physical position.

The core of the project is an Arduino and the three ultrasonic sensors. The sensors act as range finders, and when they are all working together under the direction of the microcontroller they can tell which direction a hand was moving when it passed by. This information is used to drive two servos, one in the base and one on the lamp’s arm.

The project requires an articulating desk lamp of some sort (others besides the specific one [Daniel] used shouldn’t be much of a problem as long as they bend in the same way). Most hackers will have the rest of the parts on hand, with the possible exception of the rangefinder. The code is up on the project site for a look-see or in case you want to build your own.

The only problem that [Daniel] had when putting this all together was that the base was a little wobbly. He was able to fix that with some thumbtacks, and we think the next step for the project should be switching the light on and off over the internet.

A Virtual Touchscreen (3D Ultrasonic Radar)


Producing items onto a screen simply by touching the air is a marvelous thing. One way to accomplish this involves four HC-SR04 ultrasonic sensor units that transmit data through an Arduino into a Linux computer. The end result is a virtual touchscreen that can be made at home.

The software of this device was developed by [Anatoly] who translated hand gestures into actionable commands. The sensors attached to the Arduino had an approximate scanning range of 3m, and the ultrasonic units were modified to broadcast an analog signal at 40 kHz. There were a few limitations with the original hardware design as [Anatoly] stated in the post. For example, at first, only one unit was transmitting at a time, so there was no way the Arduino could identify two objects on the same sphere. However, [Anatoly] updated the blog with a 2nd post showing that sensing multiple items at once could be done. Occasionally, the range would be finicky when dealing with small items like pens. But besides that, it seemed to work pretty well.

Additional technical specifications can be found on [Anatoly]’s blog and videos of the system working can be seen after the break.

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Using Ultrasonic Sensors to Measure and Log Oil Tank Levels

[Mike] lives in a temperate rainforest in Alaska (we figured from his website’s name) and uses a 570 gallon oil tank to supply his furnace. Until now, he had no way of knowing how much oil was left in the tank and what his daily usage was. As he didn’t find any commercial product that could do what he wanted, he designed his own solution. In his write-up, [Mike] started by listing all the different sensors he had considered to measure the oil level and finally opted for an ultrasonic sensor. In his opinion, this kind of sensor is the best compromise between cost, ease of use, range and precision for his application. The precise chosen model was the ping))) bought from our favorite auction website for around $2.5.

[Mike] built the custom enclosure that you can see in the picture above using PVC parts. Enclosed are the ultrasonic sensor, a temperature sensor and an LED indicating the power status. On the other side of the CAT5 cable can be found an Arduino compatible board with an XBee shield and a 9V battery. Using another XBee shield and its USB adapter board, [Mike] can now wirelessly access the tank oil level log from his computer.

We are the Borg. We will add heat and distance sensing to your vision.


[Gregory McRoberts] was born with reduced vision in one eye and has never experienced the three dimensional sight which most of us take for granted. Recently he was inspired by the concept of a hearing aid to build a device which can augment his vision. Behold, the very Borg-like eye-patch that he wears to add distance and heat to his palette of senses.

The hardware he chose is an Arduino-compatible Lilypad board. It is wired to an ultrasonic rangefinder and an infrared sensor which monitor the area in front of him. The function of his right eye is still capable of seeing light and color, so a pair of LED boards are mounted on the inside. One is connected to the thermal sensor, displaying blue when below eighty degrees Fahrenheit and red when above. The other LED is green and flashes at a different speed based on the range sensor’s reading.

This is distracting when a person with normal sight wears it because of the intensity of the LEDs. We found [Gregory’s] explanation of this (called Helmet Fire) quite interesting.

[via Adafruit]

$15 toy becomes fully programmable robot

[Kevin] undertook a robot build partly for his own enjoyment, but also to include his kids in the action. He acquired a cheap toy and packed it full of programmable goodness. The starting point was a $15 toy called Rad 2.0. It’s a great starting point as it already included some motorized parts, and takes care of much of the mechanical issues like joints and structure.

The image on the left is the fourth update which [Kevin] has posted. The robot now responds to voice commands (with the same syntax as Chippu uses), moving its gaze to face forward or to either side. You’ll notice there’s a wireless webcam which lets him spy on what’s in front of the robot’s gaze. An ultrasonic range finder makes itself at home in the beak of the bot, and a Larson Scanner is nestled in the brow using the kit from Evil Mad Scientist Labs. Check out the video after the break for an overview of the hardware modifications.

The build log for this project is a forum post. That forum is run by [DJ Sures], a veteran at taking cheap toys and making them awesome. It seems like he’s taken a web forum and made it awesome too because the conversation about [Kevin’s] project is packed with constructive tips and encouragement.

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Halloween Hacks: Motion sensing fog machine

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[monkeysinacan] wanted to add a fog machine to his Halloween display, but he says that the cheaper consumer-grade models are pretty unruly beasts. He cites short duty cycles and tricky fog control as his two biggest gripes with these sorts of foggers. He decided make the fogging process a little more manageable, and modified his to only generate fog when someone was walking nearby.

One obvious concern with this sort of setup is the warm-up time required to get the device ready to produce fog. If it were to only turn on when someone walked by, [monkeysinacan] would miss his mark each and every time. To ensure that his machine was accurate, he rigged it so that the heat exchanger stayed powered on, triggering the fog juice pump as needed.

To do this, he used an ultrasonic sensor similar to, but cheaper than a Parallax Ping unit. Paired with an Arduino, the sensor triggers the fog machine’s pump for 20 seconds whenever anyone gets within 6 feet of it.

While he hasn’t posted video of the modified fogger at work, it sounds like a solid plan to us.