Sometimes it’s necessary to make do with whatever parts one has on hand, but the results of squashing a square peg into a round hole are not always as elegant as [Juan Gg]’s programmable DC load with rotary encoder. [Juan] took a design for a programmable DC load and made it his own in quite a few different ways, including a slick 3D-printed enclosure and color faceplate.

The first thing to catch one’s eye might be that leftmost seven-segment digit. There is a simple reason it doesn’t match its neighbors: [Juan] had to use what he had available, and that meant a mismatched digit. Fortunately, 3D printing one’s own enclosure meant it could be gracefully worked into the design, instead of getting a Dremel or utility knife involved. The next is a bit less obvious: the display lacked a decimal point in the second digit position, so an LED tucked in underneath does the job. Finally, the knob on the right could reasonably be thought to be a rotary encoder, but it’s actually connected to a small DC motor. By biasing the motor with a small DC voltage applied to one lead and reading the resulting voltage from the other, the knob’s speed and direction can be detected, doing a serviceable job as rotary encoder substitute.

The project’s GitHub repository contains the Arduino code for [Juan]’s project, which has its roots in a design EEVblog detailed for an electronic load. For those of you who prefer your DIY rotary encoders to send discrete clicks and pulses instead of an analog voltage, a 3D printed wheel and two microswitches will do the job.

Regular icosahedrons are 20-sided polyhedrons formed out of equilateral triangles. As such, the geometry behind making one is slightly complicated, but the results in the case of this large light-up device appear to have been well worth it.

The project’s write-up does go over how to actually model these faces in CAD but also provides the 3D print files if you’d like to skip to building your own. Two versions were made, including a device that illuminates RGBW LEDs under Arduino Nano control, and a second icosahedron large enough to be used as a lamp shade! 

A demo/explanation is seen in the first clip below, along with a better look at the electronics in the breadboard video.

Depending on your personality, you may tend to dominate a discussion, or metaphorically slink back into the corner, waiting for a turn to speak that never comes. MIT Tangible Media Group’s SociaBowl, however, aims to change this as “a dynamic table centerpiece to mediate group conversations.”

SociaBowl takes the form of a circular standing table, with a rather curious servo-actuated bowl in the center. Copper wires embedded in the table’s acrylic surface, along with a capacitive touch shield pick up user inputs. 

An Arduino Uno then translates into bowl motion, which can mean a reward for thoughtful speakers when the bowl is filled with candy, or in another implementation, the possibility of water inside spilling if one chats for too long. 

For more info, check out the team’s research paper here.

[Edward], creator of the Cave Pearl project, an underwater data logger, needed a way to measure temperature with a microcontroller. Normally, this problem is most easily solved by throwing a temperature sensor on the I2C bus — these sensors are cheap and readily available. This isn’t about connecting a temperature sensor in your Arduino. This build is about using the temperature sensor in your clock.

The ATMega328p, the chip at the heart of all your Arduino Uno clones, has within it a watchdog timer that clicks over at a rate of 110 kHz. This watchdog timer is somewhat sensitive to temperature, and by measuring this temperature sensor you can get some idea of the temperature of the epoxy blob that is a modern microcontroller. The trick is calibrating the watchdog timer, which was done with a homemade ‘calibration box’ in a freezer consisting of two very heavy ceramic pots with a bag of rice between them to add thermal mass (you can’t do this with water because you’re putting it in a freezer and antique crocks are somewhat valuable).

By repeatedly taking the microcontroller through a couple of freeze-thaw cycles, [Edward] was able to calibrate this watchdog timer to a resolution of about 0.0025°C, which is more than enough for just about any sensor application. Discussions of accuracy and precision notwithstanding, it’s pretty good.

This technique measures the temperature of the microcontroller with an accuracy of 0.005°C or better, and it’s using it with just the interrupt timer. That’s not to say this is the only way to measure the temperature of an ATMega; some of these chips have temperature sensors built right into them, and we’ve seen projects that use this before. However, this documented feature that’s clearly in the datasheet seems not to be used by many people.

Thanks [jan] for sending this in.

Interactive video games take many forms, but for the most part, each player has a separate controller that manipulates an onscreen character, vehicle, or other singular element. What if, as in real life, multiple players have to work together with physical objects to control a sailing ship?

That’s the idea behind HOT SWAP: All Hands On Deck by Peter Gyory and Celment Zheng. In it, two players guide various parts of a ship using five different control elements. What makes this really interesting is that each player’s input device has room for two of these control elements, which must be swapped for actions such as steering and to load cannons. Input information is passed to the game via an Arduino Micro. 

It’s like if we took a regular game controller, popped off all of the inputs, and made it so you could only use a couple of them at a time. There are two controllers, with each consisting of two input slots. Each controller controls one side of the ship, port or starboard. There are five actions total in the game, each executed with a dedicated physical input: a crank to raise and lower the sails, a wheel for turning the rudder, a hatch for loading the cannons, a wick for firing the cannons, and a flame button for dousing the fire.

There is only one of each input, which makes them a shared resource that players must trade back and forth as they play. There is this old Milton Bradley kids board game from the ’90s called Perfection where players must fit shapes into holes before a timer is up and the board shakes to make everything pop out. HOT SWAP is like if Perfection had a screen attached and had a goal outside of putting shapes into slots.

All of the code is done with JavaScript and the library Three.js, which we bundle into a desktop application using Github’s Electron. The brain of the controller is an Arduino Micro, which mostly just passes data along.

The inputs are created with the Mechamagnets technique that Clement has been developing through his research; all 3D-printed in PLA with neodymium magnets embedded in them. The actual “hot swapping” is facilitated by pogo pins that line up with our custom PCBs for each input. Also, lots of chocolate croissants.

More details on the build are available via this interview as well as in the video below.

If you want a DC power supply that works well, there are a number of places to buy such a device. If, however, you want to learn how one operates, and perhaps build your own, the video below by YouTuber Electronoobs will show you how to accomplish this feat.

His project uses a transformer to step power down from the 230VAC available in Spain, along with a rectifier to produce DC current, and a capacitor to keep the output steady. An Arduino Nano produces a PWM signal that controls a MOSFET on the buck converter circuit, tuning the output voltage and current as needed based on user inputs. 

Details can be found on Electronoobs’ website here, though you’ll want to use extreme caution when dealing with mains power. Also, the design will need to be modified if your country uses something other than 230VAC.

Woodworking with power tools creates dust. Lots of it. Hooking a vacuum up to your tool helps greatly, but only if it’s actually running. Annoyed with turning on his vacuum system every time he had to make a cut, Zach Hipps decided to automate the process.

What he came up with uses an ACS712 current sensor to detect when power is flowing to his table saw, and an Arduino Nano for control. When current is sensed, it triggers the vacuum using a relay, then holds it on until five seconds after the device is turned off. 

If I’m going to be able to automatically turn on the shop vac, I need to be able to detect when the tool is turned on and running. Without modifying the tool, the best way to do this is to get a current sensor like the ACS712 which I also got on eBay for a couple of bucks. This sensor can read alternating or direct current up to 20 Amps which is perfect for what I’m going to be using it for. The sensor outputs an analog voltage between 0 and 5 Volts that is proportional to the current it senses. I can read that analog voltage output with one of the ADC pins on the Arduino. Once I sense that the tool is running, I need to be able to turn on the shop vac. For that I’m going to use the relay module. A simple high or low logic signal from one of the Arduino’s digital pins is all that is needed to turn on the relay. 

After I had the two modules soldered to the Arduino, I decided to model and 3D print an enclosure that will secure everything in place. With the enclosure done, I can wire in the AC power receptacles. One receptacle for the tool and one for the shop vac. Having these will make it easy to move this around my garage and plug in various tools. I bought an extension cord to use for this project and cut off about 8 inches of the male end.

Build details are shown below and can also be found in Hipps’ write-up.

turn your arduino into a smart switch to automate tasks in the shop

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As previously announced, the Arduino IoT Cloud is an easy to use Internet of Things application platform that enables developers to go from unboxing their board to a working device in just minutes.

To help you get started, we’ve put together a quick project that’ll walk you through connecting a MKR1000 (or MKR WiFi 1010) to the Arduino IoT Cloud.

By the end of the tutorial, you’ll be able to control and monitor your board over the Internet using the Arduino IoT Cloud site.

First, we’ll add the board to the Arduino IoT Cloud as a Thing — a representation of the board in the cloud. We’ll then give the Thing a set of Properties which represent sensors, LEDs, motors, and many other components in the project that you’ll want to access from the cloud.

Want to see more? You can find the entire step-by-step guide here.

Do you enjoy mowing your lawn? No? Well now you can ‘simply’ print a robot to do it for you, based on German mechanical engineer Philip Read’s design. His Roomba-esque device uses a pair of gearmotors for movement, an array of three ultrasonic sensors for obstacle avoidance, and a perimeter wire/sensor to keep it within the designated boundary.

An Arduino Mega is employed as the main processing unit for the robotic mower, however a separate Nano onboard helps measure battery voltage as well as current when charging. Meanwhile, an Arduino Uno along with a motor driver are used to control the perimeter wire setup. 

Extensive build info is available on the project’s write-up, and a short demo can be seen in the video below.

Fully autonomous robot lawn mower. The mower project includes the mower itself a boundary wire control station and an optional charging station.  The mower navigates within the boundary wire which is positioned (pinned) around the perimeter of the garden. Once the mower senses the perimeter wire, it stops reverses and moves off in a new direction. The mower also has 3 sonar sensors to detect objects in the mowers path. Once the mowers battery is exhausted, the mower uses the boundary wire to navigate itself back to the charging station. All this can be customised in the Arduino software or completely re-written to your personal preferences.

Commercial mowers with this specification cost upwards of 600€ ($680).

Obviously, you’ll want to use such a device in an area devoid of kids or pets