Flexible, Sensitive Sensors from Silly Putty and Graphene

Everyone’s favorite viscoelastic non-Newtonian fluid has a new use, besides bouncing, stretching, and getting caught in your kid’s hair. Yes, it’s Silly Putty, and when mixed with graphene it turns out to make a dandy force sensor.

To be clear, [Jonathan Coleman] and his colleagues at Trinity College in Dublin aren’t buying the familiar plastic eggs from the local toy store for their experiments. They’re making they’re own silicone polymers, but their methods (listed in this paywalled article from the journal Science) are actually easy to replicate. They just mix silicone oil, or polydimethylsiloxane (PDMS), with boric acid, and apply a little heat. The boron compound cross-links the PDMS and makes a substance very similar to the bouncy putty. The lab also synthesizes its own graphene by sonicating graphite in a solvent and isolating the graphene with centrifugation and filtration; that might be a little hard for the home gamer to accomplish, but we’ve covered a DIY synthesis before, so it should be possible.

With the raw materials in hand, it’s a simple matter of mixing and kneading, and you’ve got a flexible, stretchable sensor. [Coleman] et al report using sensors fashioned from the mixture to detect the pulse in the carotid artery and even watch the footsteps of a spider. It looks like fun stuff to play with, and we can see tons of applications for flexible, inert strain sensors like these.

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Detecting Water With and Without Headaches

In Texas — at least around Houston — we don’t have basements. We do, however, have bilges. Both of these are subject to taking on water when no one is paying attention. A friend of mine asked me what I thought of an Instructable that showed how to make a water sensor using a few discrete components. The circuit would probably work — it relied on the conductivity of most water to supply enough current to a bipolar transistor’s base to turn it on.

It is easy to overthink something like this, so I told my friend he should go with something a little more old-fashioned. I don’t know the origin of it, but it is older than I am. You can make a perfectly good water detector with things you probably already have around the house. My point isn’t that you should (or shouldn’t) construct a homemade water sensor. My point is that you don’t always need to go to the high-tech solution.

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Biologically Inspired Sensors Turned Into Silicon

For the last three and a half Billion years, evolution has built sensors. The nerves on your fingertips are just as good as any electronic touch sensor, a retina is able to detect a single photon, and the human ear is more finely tuned than the best microphones.

At the 2016 Hackaday SuperConference, Dr. Christal Gordon, educator and engineer, talked about the hardware behind our wetware. While AI researchers are still wondering if they have to define consciousness, there’s still a lot that medicine, psychology, and neuroscience can teach us about building better hardware with simple tools, just like nature has been doing for Billions of years.

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Ikea Desk Lamp That Will Defend Your Lungs

While some people may enjoy the occasional whiff of noxious smells — gasoline, axe body spray, etc — prolonged exposure to fumes is not good for your health. This goes for soldering too, isn’t it about time you added some abatement to your bench tools?

Inspired by some of the fume hoods we’ve featured before — take note, ye who art lacking projects — [Georg Sluyterman] put together his own Ikea lamp fume extractor.

The most striking feature is that it’s mounted on an Ikea desk lamp making for convenient positioning and minimal clutter. A NeoPixels strip lights up your soldering space while the PIR sensor activates the fan when it detects movement. A WeMos D1 Mini is included for WiFi connectivity but that feature still down the road a little bit. The functionality that is in place is still quite impressive; more on that after the break.

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DIY I2C Devices with ATtiny85

[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.

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Bright by Day, Dark by Night!

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?)

Bathroom Status Reporting Hack Eliminates Lines, Frustration

In a lot of ways, portable toilets are superior to standard indoor-plumbing-style toilets. This is mostly due to the fact that they have a status indicator on the door. It’s a shame that no indoor bathrooms have figured this out yet, especially in office buildings where your awkward coworkers bang on every door rather than just check for feet in the huge gap that for some reason exists between the floor and the stall door. Anyway, [Chris] and [Daniel] came up with a solution for this issue, which also eliminates wait time for bathrooms in their office.

Their system is an automated bathroom status indicator that reports information about the bathroom’s use over WiFi. Since the bathrooms at their facility are spread out, it was helpful to be able to look up which bathroom would be free at any given moment. Several Raspberry Pis form the nerves of the project. Custom sensors were attached to a variety of different door locks to detect status. Each Pi reports back over WiFi. This accomplishes their goal of being subtle and simple. They also point out that they had to write very little code for this project since there are so many Unix and embedded hardware tools available to them. Checking the status of the bathroom can be as simple as running netcat.

If you’re looking to roll out your own bathroom status monitor solution, [Chris] and [Daniel] have made their code available on GitHub. There are a number of other ways to automate your bathroom, too, like switching the exhaust fan on when it gets too smelly or humid, or even creating a device that dispenses your toilet paper for you.

 

Musical Proximity Detection Pet Bowls

An essential skill for a maker is the ability to improvise or re-purpose existing materials into new parts. Sometimes, one needn’t make many modifications to create something new, as is the case with [Robin Sterling] and his musical pet bowl.

Originally, it was a sealed pet bowl that opened when the proximity sensors detected an approaching pet. Having helped design the bowl, [Sterling] had a bit of an advantage when he decided to convert it into a theremin/light harp-esque instrument for the company BBQ. He routed the PWM outputs from each of the three proximity sensors (in each of the three bowls) to a small guitar amp, adjusting each sensor’s output to a different frequency. Despite the short amount of time [Sterling] had to practice, it works fairly well!

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