Gravity Defying Drips of a Bike Pump Controlled Fountain

People love to see a trick that fools their senses. This truism was in play at the Crash Space booth this weekend as [Steve Goldstein] and [Kevin Jordan] showed off a drip fountain controlled by a bike pump.

These optical illusion drip fountains use strobing light to seemingly freeze dripping water in mid-air. We’ve seen this before several times (the work of Hackaday alum [Mathieu Stephan] comes to mind) but never with a user input quite as delightful as a bike pump. It’s connected to an air pressure sensor that is monitored by the Arduino that strobes the lights. As someone works the pump, the falling droplets appear to slow, stop, and then begin flowing against gravity.

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Precision Pressure In A Piston

[Scott] is building a DIY yeast reactor for his aquarium. What’s a yeast reactor? [Scott] wants to pump carbon dioxide into his aquarium so his aquatic plants grow more. He’s doing this with a gallon of sugary, yeasty water bubbling into a tank of plants and fish. In other words, [Scott] is doing this whole thing completely backward and utilizing the wrong waste product of the yeast metabolism.

However, along the way to pumping carbon dioxide into his aquarium, [Scott] created a very high precision pressure sensor. It’s based on a breakout board featuring the MS5611 air pressure sensor. This has a 24-bit ADC on board, which translates into one ten-thousandths of a pound per square inch of pressure.

To integrate this pressure sensor into the aquarium/unbrewery setup, [Scott] created a pressure meter out of a syringe. With the plunger end of this syringe encased in epoxy and the pointy end still able to accept needles, [Scott] is able to easily plug this sensor into his yeast reactor. The data from the sensor is accessible over I2C, and a simple circuit with an ATmega328 and a character LCD displays the current pressure in the syringe.

We’ve seen these high-resolution pressure sensors used in drones and rockets as altimeters before, but never as a pressure gauge. This, though, is a cheap and novel solution for measuring pressures between a vacuum and a bit over one atmosphere.

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Reviving a Dead Zanzithophone

It’s great to hear from people who say they’re inspired to fix stuff by reading about hacks here on Hackaday. [Michael Lüftenegger] from Salzburg is one of them. About a year back, he snagged a digital horn from eBay that turned out to be dead-er than advertised and he wrote a post about how he fixed it and gave it a second life.

The Casio DH-100 is an electronic MIDI digital wind controller/synthesizer musical instrument. Your breath flows through the instrument, making it feel pretty similar to acoustic wind instruments. [Michael]’s unit had already seen some attempted, but unsuccessful repairs. Nothing that could not be fixed, except that the main pressure sensor was missing. Without the sensor, the instrument was practically useless. The eBay seller wasn’t lying when he described the unit as working with breath mode turned off!
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Push Blood Pressure Data To The Cloud Via ESP8266

[Eduardo] contacted us about his success at connecting a blood pressure monitor to the web. He pulled this off by locating the chip responsible for storing the blood pressure data after being measured. It was a simple I2C EEPROM from which he dumped the data a sniffed communications with a 4 bit logic analyzer. [Eduardo] published all of his findings on that communication scheme so check out his post for more on that. The gist of it is that he implemented his reverse engineered protocol using an ESP8266, the ubiquitous cheap WiFi board that has become a go-to for web-connected anything like power monitors and underpowered but awesome server farms. Check out the Hackaday Dictionary entry for more on this board.

[Eduardo] is not the first on the scene with such a device, you can see a Withings device and a blipcare device available on Amazon. What this hack from [Eduardo] does provide is evidence of a much cheaper route for connecting vital medical data from a geographically distant, and perhaps technophobic family member. Lets take a walk down hypothetical lane, shall we? Uncle Bob in Albuquerque who doesn’t have any local family might be a good candidate for such a hacked device, everyone knows it’s like pulling teeth to get elderly family members to report some health information to loved ones… but with [Eduardo’s] hack it’s simple. Embed the hardware (assuming you know the login creds ahead of time) into a new BPM, send it to him as a gift, and Bob’s your uncle.

We haven’t seen too many blood pressure monitor hacks, but one entry from the Hackaday Prize dubbed “the pain machine” included monitoring the user’s blood pressure. We also covered an interesting hack on monitoring your heart rate with a piezo element.

A quick demo of [Edward’s] cuff is found below.

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Temperature, Altitude, Pressure Display

During a recent trip to Bhutan, [electronut] wished for a device that would show the temperature and altitude at the various places he visited in the Kingdom. Back home after his trip, he built this simple Temperature, Altitude and Pressure Display Device using a few off the shelf parts.

Following a brief search, he zeroed in on the BMP 180 sensor which can measure temperature and pressure, and which is available in a break-out board format from many sources. He calculates altitude based on pressure. The main parts are an Arduino Pro Mini clone, a BMP180 sensor and a Nokia 5110 LCD module. A standard 9V battery supplies juice to the device. A push button interface allows him to read the current parameters when pressed, thus conserving battery life.

Standard libraries allow him to interface the LCD and sensor easily to the Arduino. He wrapped it all up by enclosing the hardware in a custom laser cut acrylic box. The result is bigger than he would like it to be, so maybe the next iteration would use a custom PCB and a LiPo battery to shrink it in size. While at it, we think it would be nice to add a RTC and some sort of logging capability to the device so it can store data for future analysis. The schematic, code and enclosure drawing are available via his Github repository.

The Ultimate Tiny Altimeter


While traditionally a project geared more toward the model rocket crowd, a lot of people are flying quadcopters these days, and knowing the altitude your RC aircraft reached is a nice thing to know. [Will] came up with a very nice, very small, and very lightweight altimeter that’s perfect for strapping to microquads, their bigger brothers, and of course model rockets. As a nice bonus, it also looks really cool with an exceedingly retro HP bubble display.

The components used in this tiny altimeter include a MEMS altitude and pressure sensor, HP bubble display featuring four seven-segment LEDs, an Arduino Pro Mini, and a tiny 40 mAh LiPo capable of powering the whole contraption for hours.

In the video below, [Will] shows off the functions of his altimeter, sending it aloft on a quadcopter to about 100 ft. There are settings for displaying the minimum, maximum, and delta altitudes, all accessed with a single button.

While it’s not the most feature packed altimeter out there, it’s still much better than commercial offerings available for the model rocket crowd.

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Designing a pressure sensitive floor


[Sean] and his team at Adobe were asked to build “something new” for the Children’s Creativity Museum in San Francisco, so in several months they managed to build a digital/physical environment for kids called “Sense It”.

Part of this project involved designing and building a pressure-sensitive electronic floor which could detect if children were sitting, walking or running. As a camera based detection system couldn’t give them the type of precision they wanted, [Sean] decided to use pressure-sensitive resistors placed under MDF panels.

There are a total of twenty-one 2’x4′ tiles, each one including 8 pressure-sensitive resistors and an ATtiny84 based platform. All the microcontrollers digitize their 8 sensor signals and send their conversion results to a beaglebone over a shared i2c bus in a RJ45 CAT5 cable. As it is [Sean]’s first project, we will cut him some slack but several design mistakes have been made in our opinion:

  • Using i2c instead of RS485 / CAN for long distance data transmission
  • Digitizing the sensor voltages so far from them, as noise is added before the ADC
  • Sending the +5V required by the ATtiny in the RJ45 cable instead of a higher voltage (which would involve putting an LDO on the platforms)
  • Separating the digital and analog ground planes as the platform current consumption is low and transmission speeds slow

But the children who can now play with the complete system certainly won’t care. And you… what do you think of [Sean]’s work? Don’t hesitate to let us know in the comment section below.