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We’re all familiar with the experience of buying hobby servos. The market is awash with cheap clones which have inflated specs and poor performance. Even branded servos often fail to deliver, and sometimes you just can’t get the required torque or speed from the small form factor of the typical hobby servo.

Enter [James Bruton] and his DIY RC servo from a windscreen wiper motor. Windscreen wiper motors are cheap as chips, and a classic salvage. The motor shaft is connected to a potentiometer via a pulley and some string, providing the necessary closed-loop feedback. Instead of using the traditional analog circuitry found inside a servo, an Arduino provides the brains. This means PID control can be implemented on the ‘duino, and tuned to get the best response from different load characteristics. There’s also the choice of different interfacing options: though [James]’ Arduino code accepts PWM signals for a drop-in R/C servo replacement, the addition of a microcontroller means many other input signal types and protocols are available. In fact, we recently wrote about serial bus servos and their numerous advantages.

We particularly love this because of the price barrier of industrial servomotors; sure, this kind of solution doesn’t have the precision or torque that off-the-shelf products provide, but would be sufficient for many hacks. Incidentally, this is what inspired one of our favourite open source projects: ODrive, which focuses on harnessing the power of cheap brushless motors for industrial use.

Connecting your shiny new ESP8266 to WiFi can be as simple or as complicated as you please. Most people decide to manually add it. Some people find clever ways to make the bloody thing connect itself. [Eduardo Zola] transfers his WiFi password using the flashing light of a smartphone screen.

A simple photo-resistor and a bit of tinkering allows him to easily send credentials — or any data really — to his ESP8266, through the power of LiFi. Short for Light Fidelity, LiFi transmits data using light with on and off states representing digital values. It can use visible light, or reach into either the ultraviolet or infra-red radiation if need be. For the nitty-gritty details on the subject, check out our primer on LiFi.

 A flashing LCD screen and a photo-resistor barely make the cut for a one-way LiFi system, but [Eduardo Zola] makes it work. The approach is to build a resitor divider and watch an input pin on the ESP for changes.

The trick is to keep ambient light out of the mix. The test sensor shown here places the LDR in a black cap, but [Eduardo] 3D-Printed a slick little enclosure for his reverse flashlight so it fits flush with the phone screen. One click and about half a minute of a flashing screen later, and the Wi-Fi credentials are transferred. This circuit could really be added onto any project, for short data transfers. With a bit more work on the sensor circuit, speed could be improved with the limiting factor being the timing on the phone screen itself.

Since the ESP8266 has its own WiFi connection, it’s likely you’ll use that for data transfer once the LiFi gets it onto the network. But any situation where you don’t have a full user input or a network connection could benefit from this. Pull out that old scrolling LED matrix project and add this as a way to push new messages to the device!

If you have OCD, then the worst thing someone could do is give you a bowl of multi-coloured M&M’s or Skittles — or Gems if you’re in the part of the world where this was written. The candies just won’t taste good until you’ve managed to sort them in to separate coloured heaps. And if you’re a hacker, you’ll obviously build a sorting machine to do the job for you.

Use our search box and you’ll find a long list of coverage describing all manner and kinds of sorting machines. And while all of them do their designated job, 19 year old [Willem Pennings]’s m&m and Skittle Sorting Machine is the bees knees. It’s one of the best builds we’ve seen to date, looking more like a Scandinavian Appliance than a DIY hack. He’s ratcheted up a 100k views on Youtube, 900k views on imgur and almost 2.5k comments on reddit, all within a day of posting the build details on his blog.

As quite often happens, his work is based on an earlier design, but he ends up adding lots of improvements to his version. It’s got a hopper at the top for loading either m&m’s or Skittles and six bowls at the bottom to receive the color sorted candies. The user interface is just two buttons — one to select between the two candy types and another to start the sorting. The hardware is all 3D printed and laser cut. But he’s put in extra effort to clean the laser cut pieces and paint them white to give it that neat, appliance look. The white, 3D printed parts add to the appeal.

Rotating the input funnel to prevent the candies from clogging the feed pipes is an ace idea. A WS2812 LED is placed above each bowl, lighting up the bowl where the next candy will be ejected and at the same time, a WS2812 strip around the periphery of the main body lights up with the color of the detected candy, making it a treat, literally, to watch this thing in action. His blog post has more details about the build, and the video after the break shows the awesome machine in action.

And if you’re interested in checking out how this sorter compares with some of the others, check out these builds — Skittles sorting machine sorts Skittles and keeps the band happy, Anti-Entropy Machine Satiates M&M OCD, Only Eat Red Skittles? We’ve Got You Covered, and Hate Blue M&M’s? Sort Them Using the Power of an iPhone!  As we mentioned earlier, candy sorting machines are top priority for hackers.

[via r/electronics]


Filed under: Arduino Hacks, cooking hacks
Mar
31

The clever folks over at [Novaetech SRL] have unveiled openQCM, their open-source quartz crystal microbalance. A QCM measures very minute amounts of mass or mass variation using the piezoelectric properties of quartz crystal. When an object is placed on the surface of this sensor, the changes in the crystal’s resonant frequency can be detected and used to determine its mass in a variety of experimental conditions (air, vacuum, liquid). However, most QCM technology is proprietary and pricey – at least US$3000 for the microbalance itself. Any consumables, such as additional crystals, cost several hundred dollars more.

The openQCM has a sensitivity of 700 picograms. At its core is an Arduino Micro with a custom PCB. The board contains a 10K thermistor for temperature offset readings and the driver for a Pierce oscillator circuit. The quartz crystal frequency is determined by hacking the timer interrupts of the Arduino’s ATmega32u4. An external library called FreqCount uses the clock to count the number of pulses of the TTL signal in a 1 second time frame. This yields quartz crystal frequency resolution of 1Hz. The user interface is built in Java so that data can be read, plotted, and stored on your computer. The entire casing is 3D-printed, and it appears that the sensors are standard oscillator crystals without their cases.

Simplistic design makes assembly and maintenance a breeze. It only weighs 55 grams. Replacing the quartz crystal requires no special tools due to the clip system. The openQCM can be used as a single unit, or in multiples to form a network for all of your precise measurement needs. While they have kits available that will set you back US$500, all of the files and schematics for 3D-printing, assembly, and the PCB are available on the openQCM site for free.

[Special Thanks to Augustineas for sending us this tip!]

 

 


Filed under: Arduino Hacks, chemistry hacks


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