BlueMatrix: An Arduino-based LED matrix display

Designed by Dentella Luca, BlueMatrix can be controlled remotely via a PC, smartphone or tablet.

Key project components include:

• An Atmel-based Arduino Uno (ATmega328 MCU)
• 
LED matrix display based on the HC1632C controller
• 
Lipo Rider
• 
Lipo Fuel Gauge
• 
HC-05 Bluetooth module
• 5mm plexiglas enclosure

The modules are connected as follows:

“The Arduino Uno is the heart of the project, [as] it manages the display, checks the battery status and talks (using a simple protocol) with the controlling device (Windows application or Android app),” Luca explained in a recent blog post.

“The BlueMatrix is powered by a Li-po battery (1 cell). The battery’s state of charge is monitored by Lipo Fuel Gauge, which sends the actual SoC (State of Charge) value to Arduino via I2C bus. The Lipo Rider module rises the battery voltage to 5V to power all the other modules and allows it to recharge the battery using a simple, mini-USB power supply.”

Meanwhile, the HC-05 module is tasked with managing Bluetooth connectivity.

“After having established the connection with the remote device, it transparently transport the data received/transmitted by Arduino via serial connection,” said Luca.

On the software side, Luca developed two applications to control BlueMatrix: a .Net application (developed in C#) and an Android app.

“BlueMatrix was designed to be portable, therefore I suppose that it will be mostly controlled using a smartphone; this is the reason why the Android app is better designed than the desktop one and it’s also available on Google’s Play Store,” he added.

Interested in learning more? You can check out the official BlueMatrix project page here and download the Arduino sketch on GitHub here.

Video: Designing a trainable robotic arm

A YouTube user by the name of navic209 has designed a trainable robotic arm built around Adafruit’s Analog Feedback Micro Servo and an Atmel-powered Arduino board that can be easily “taught” to move in a specific pattern.

Once the “train” button is pressed, users simply move the arm and gripper in a specific pattern, while an Atmel-powered Arduino board stores the relevant positions in EEPROM. The arm is then fully capable of precisely replaying the various motions.

According to navic209, the trainable robotic arm was inspired by Baxter, an entirely new robot targeted at manufacturing environments. Indeed, Baxter performs a variety of repetitive production tasks – all while safely and intelligently working next to people.

Interested in learning more about the Atmel-powered trainable robotic arm? The Arduino sketch is available on Github, while Adafruit’s Analog Feedback Micro Servo can be purchased here. The micro servo robotic arm is available on Thingiverse, along with the micro servo gripper (also on Thingiverse).

Build your own metal detector with an Arduino

A Maker by the name of Dzl (and son) recently built his very own metal detector using an Atmel-based Arduino.

“Most metal detectors use a search coil that act as part of an oscillator circuit. When metal is put in proximity of the search coil both the frequency of the oscillation changes. Many metal detectors uses another more stable oscillator BFO (beat frequency oscillator) to act as a reference for the frequency of the search coil,” Dzl wrote in a blog post.

“Usually the frequency of the BFO is adjusted to exactly match that of the search coil oscillator when no metal is present near this. The signals from these two oscillators are then fed to a (usually analog) circuit that creates an output proportionally to the difference in frequency of the two. This may be either an audible tone and/or some meter reading.”

However, says Dzl, another device that is quite handy at detecting minute frequency changes is a versatile microcontroller (MCU).

“[So] we decided to swap the BFO approach for a microcontroller and came up with [a] simple circuit. The oscillator circuit feeds a 160kHz signal to pin 5 of the Arduino. The Arduino sketch then measures the frequency of this pin very accurately,” Dzl explained.

“When the ‘NULL SW’ button is held this frequency is stored. Any deviation from this frequency is then represented as a series of ‘geiger counter’ clicks on the piezo. The rate of the clicks increases as metal approaches the coil.”

Dzl says he and his son tried a number of different search coils, discovering that approximately 30 turns of wire around a 15cm. plastic bucket worked quite well.

“All we needed then was to tie it all to a discarded Ikea lamp – and hey-presto off to the beach to find treasures. The metal detector has excellent sensitivity and by changing the SENSITIVITY value in the Arduino sketch you are able to tune it for both small and large objects,” he added.

Want to try building your own metal detector with an Arduino? Check out the source code here.