Students Set Sights on DIY Eye Exams

What if you could give yourself a standard eye exam at home? That’s the idea behind [Joel, Margot, and Yuchen]’s final project for [Bruce Land]’s ECE 4760—simulating the standard Snellen eye chart that tests visual acuity from an actual or simulated distance of 20 feet.

This test is a bit different, though. Letters are presented one by one on a TFT display, and the user must identify each letter by speaking into a microphone. As long as the user guesses correctly, the system shows smaller and smaller letters until the size equivalent to the 20/20 line of the Snellen chart is reached.

Since the project relies on speech recognition, the group had to consider things like background noise and the differences in human voices. They use a bandpass filter to screen out frequencies that fall outside the human vocal range. In order to determine the letter spoken, the PIC32 collects the first 256 and last 256 samples, stores them in two arrays, and performs FFT on the first set. The second set of samples undergoe Mel transformation, which helps the PIC assess the sample logarithmically. Finally, the system determines whether it should show a new letter at the same size, a new letter at a smaller size, or end the exam.

While this is not meant to replace eye exams done by certified professionals, it is an interesting project that is true to the principles of the Snellen eye chart. The only thing that might make this better is an e-ink display to make the letters crisp. We’d like to see Snellen’s tumbling E chart implemented as well for children who don’t yet know the alphabet, although that would probably require a vastly different input method. Be sure to check out the demonstration video after the break.

Don’t know who [Bruce Land] is? Of course he’s an esteemed Senior Lecturer at Cornell University. But he’s also extremely active on, has many great embedded engineering lectures you can watch free-of-charge, and every year we look forward to seeing the projects — like this one — dreamed and realized by his students. Do you have final projects of your own to show off? Don’t be shy about sending in a tip!

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DIY Lamps Brighten Winter Blues

As you know, winter is coming. For a lot of people this means that Seasonal Affective Disorder is beginning to set in. [Luke]’s mom already has a light therapy box. It’s one of those commercially available ones that uses fluorescent bulbs and leaves a lot to be desired in the full-spectrum light simulation department. [Luke] jumped on the opportunity to design a better one.

The standard of quality for light therapy units is a rating of 10,000 lux. While lux definitely matters, the rating is a misleading selling point when given on its own. One of the other important factors in mimicking the sun is the Color Rendering Index (CRI). CRI is basically a rating of the bulb’s ability to imitate the color reproduction of natural daylight. The ratings run from 0 to 100 but in reality, the highest-rated bulbs of any kind top out around 98.

For all the fluorescent bulb-bearing light therapy units out there, those bulbs have pretty low CRI ratings. [Luke]’s project page provides emission spectra graphs for a number of bulb types, and we can see how his choice of ceramic metal halide bulbs stacks up against fluorescent, incandescent, and LED bulbs. One of the few downsides to this type of bulb is that they have long startup times.

He ended up making two light therapy lamps, one of them directional and the other omni-directional. They both use ballast-controlled ceramic metal halide bulbs. The ballasts are necessary to provide the high starting voltage that these bulbs require. The omni-directional light is built into a large hurricane candle holder. A lamp holder is fixed into the base and wired to an external ballast box. The directional lamp is a self-contained unit, and [Luke] is happiest with this one. It’s flat and rugged so it can be placed on top of a bookcase and the light bounced off of the ceiling for pleasant, indirect coverage.

We’ve seen a couple of alarm-clock wakeup light builds here, and we’re thinking this would make an awesome mashup.

Your Handwriting Is Now Your Font

They say your handwriting is as unique to you as is your fingerprint. Maybe they are right – perhaps every person adds a little bit of his or her personality to their penmanship. Just maybe there are enough ways to vary pressure, speed, stroke, and a dozen other almost imperceptible factors that all 7 billion of us have a slightly different style.

The study of handwriting is called Graphology, and people have been at it for a quite a long time. Most experts agree that a person’s handwriting can reveal their gender, where it starts to get fuzzy is that others claim they can tell much more including age, race, weight, and even mood. Going further down the rabbit hole, some employers have tried to use handwriting analysis to determine if an applicant is a match for a position. That seems a bit of a stretch to us.

Now, if you want to digitize a tiny bit of what makes you, you – then all you have to do it to fill out this (PDF) form and upload it to the interwebs. Out the other end will pop a true type font that you can save for yourself or share with the world. Why would you want to do that? This hack caught our eye as a way of adding annotations to our work in a more informal, yet still personal manner. Or maybe we just wanted to upload it to the cloud in hopes it would live forever. Either way, if you want to see some really amazing style, head on over to the “Penmanship Porn” subreddit where you can find some amazing chicken scratch.

See Who’s Calling with Caller Pi-D

One of the hardest things in life is watching your parents grow old. As their senses fail, the simplest things become difficult or even impossible for them to do.

[kjepper]’s mom is slowly losing her sight. As a result, it’s hard for her to see things like the readout on the caller ID. Sure, there are plenty of units and phones she could get that have text-to-speech capabilities, but the audio on those things is usually pretty garbled. And yes, a smartphone can natively display a picture of the person calling, but [kjepper]’s mom isn’t technologically savvy and doesn’t need everything else that comes with a smartphone. What she needs is a really simple interface which makes it clear who’s calling.

Initially, [kjepper] tried to capture the caller ID data using only a USB modem. But for whatever reason, it didn’t work until he added an FSKDTMF converter between the modem and the Pi. He wrote some Node.js in order to communicate with the Pi and send the information to the screen, which can display up to four calls at once.  To make a mom-friendly interface, he stripped an old optical mouse down to the scroll wheel and encased it in wood. Mom can spin the wheel to wake the system up from standby, and click it to mark the calls as read. Now whenever Aunt Judy calls the landline, it’s immediately obvious that it’s her and not some telemarketer.

[via r/DIY]

Sensor Net Makes Life Easier for Rice Farmers

Rice is cultivated all over the world in fields known as rice paddies and it is one of the most maintenance intensive crops to grow. The rice paddy itself requires a large part of that maintenance. It is flooded with water that must be kept at a constant level, just below the height that would keep rice seedlings from growing but high enough to drown any weeds that would compete with the rice stalks for nutrients. This technique is called continuous flooding and a big part of the job of a rice farmer is to inspect the rice paddy every day to make sure the water levels are normal and there are no cracks or holes that could lead to water leakage.

This process is labor intensive, and the technology in use hasn’t changed much over the centuries. Most of the rice farmers in my area are elders with the approximate age of 65-70 years. For these hard working people a little bit of technology can make a big difference in their lives. This is the idea behind TechRice.

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This PCB Business Card is Logically Different

Having seen a number of PCB business cards [Will] decided to go against the more popular choice of a micro-controller based design and show some character with a logic based finite state machine. [Will] uses a single 7-segment display to scroll through the letters of his name with a state machine that outputs the desired combination of 1’s and 0’s to the LED display each time the tactile button is pushed.

[Will] uses a 4-bit counter made up of D Flip-Flops for the clock signal as a conditional input to 6 of the 4-input AND gates. He doesn’t go into the painful details of displaying each character through the process (thankfully) but he does mention that he uses the Quine-McCluskey technique for reduction instead of Boolean algebra. Since his name is 11 characters long and the 4-bit binary counter goes from 0000 to 1111 leaving 5 more pushes of the button before rolling the count back to 0000, during which time the display is left blank. [Will] kindly includes the eagle and Gerber files for your downloading pleasure over at his blog if you’re interested in getting a little deeper into the design.

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Hacking Eating Tracking

There’s a great hackathon going on this weekend in the Boston area. Hacking Eating Tracking challenges participants to develop technology that will help guide personal behavior toward a healthier lifestyle.

The event in hosted in Cambridge, MA by Harvard University. It isn’t focused on giving you a diet that you need to follow. It looks instead at how some more abstract behavior changes will cause your body to do this for you. One really quick example is to change the hand in which you hold your fork, or swap out the fork for a different utensil. Going “lefty” while you eat can change the cadence of your consumption and my impact how many calories you consume before feeling full. This is a really fun type of hacking to delve into!

Hackaday is one of the Hackathon sponsors and [Sophi] is headed out to participate in the weekend of building. She’s planning to work with a Pixy Camera which can measure depth data and can separate colors. Of course decisions on the build direction won’t be made until she and her teammates put their heads together, but she did have a few preliminary ideas. Several of these cameras might be used in a supermarket to gather data on where customers tend to congregate and how aisle flow and stock choices might be able to change behavior.

If you’re not in the area you should still be able to follow along as the event helps to improve people’s lives through behavior. The hackathon will be using the Hackathon framework. Teams will register and update their projects throughout the weekend. We’re looking forward to seeing what is built using the crate of LightBlue Bean boards we sent along from the Hackaday Store.