Category Archives: Electronics

Robot Arm Servo Controller

My son and I thought it would be fun project to build a meArm robot arm. If you haven’t heard of the meArm, go check out their website, or download the files to make your own over on thigiverse.

The brains board that meArm sells for controlling the thing is pretty pricey, so we thought we would just design our own.  The setup is actually two boards. The larger board is processor board, and the smaller one is the joystick board.

The processor board will attach to the meArm base, and uses a cheap Arduino Pro Mini clone that you can get off ebay for around $3, to controll the servos. The processor board also has a few extra IO pins that could be used for extra servos (I’m thinking of a base with two continuous rotation servos driving wheels) or other sensors, and a IR receiver so that it can be controlled with a IR remote such as your TV remote, or the LEGO power function remote.

The small board is the joystick board. It accommodates 2 analog joysticks and 3 push buttons. The joystick board is connected to the processor board with a ribbon cable.

Processor board on left, and joystick board on right
The processor board will connect to the joystick board with a ribbon cable

I designed the boards up in Altium, and I’m in the process of converting the files¬†over to CircuitWorks so that I can release them, so stay tuned if you are interested in using the design.

Split – Arduino based RFM22B 433/868/915 MHz wireless module

Top side of Split RF module
Bottom side of Split RF module. Notice the counter sunk LEDs in the upper left corner.

UPDATE May 15 2013: Split is now available for sale on our website

We’ve been slowly working away on an Arduino based wireless module called “Split” and just got the first real prototypes assembled and working over the last week. The module is based around a Atmega328P and a RFM22B wireless module, so it is kind of like a cross between a Arduino Pro Mini and a RFM22B breadout board.

Specs and Features:

  • Operating voltage: 3.3V
  • Processor: Atmega328P with Arduino bootloader
  • RF Frequency Range: 433MHz, 868MHz, or 915MHz ISM band (depending on version)
  • RF data rate: adjustable from 0.123 to 256kbps
  • RF output power: adjustable from 1 dBm to 20 dBm
  • RF receive sensitivity: -121 dBm
  • Long range up to several Km with proper antennas
  • On board 3.3V regulator
  • PCB Size: 20mm x 38mm
  • All processor IO pins are brought out to header pins
  • Breadboard compatible
  • Programmed with FTDI Pro
  • A user LED and button connected to IO pins
  • Slide switch to allow the DTR signal from the FTDI Pro to be directed to an IO pin to allow programming of a remote Arduino processor

Split RF module connected to a FTDI Pro

There are three main ways we envisioned Split being used:

  1. As a standalone processor with wireless capability.
  2. As a generic wireless UART link with remote DTR control to allow communicating with and programming of a Arduino processor attached to the remote Split module.
  3. As a wireless IO link. Input pins on one end are mapped to output pins on the other end and vice versa.

We’ve done some initial testing with the RF22 library from and it seems to work so that covers #1, and we are in the process of writing firmware for #2 and #3.

We are pretty excited about the long range wireless capabilities Split will give to a lot of projects.

Split RF module connected to the Mongoose IMU

User switch and LED at top.

If you are interested in this project, leave some feedback or a comment. Once we know how much interest there is, we can make some better plans for a release date.

Mongoose 9 DOF almost ready to launch!

Mongoose – the 9 DOF IMU with barometric sensor, and lots of other cool features – is almost ready for launch!!

We based our design on the popular Sparkfun Razor, updated the magnetometer, added a barometric pressure sensor, and improved utility and usability with a few other design features.

We’ve also taken the AHRS firmware written by Jordi Munoz and updated it to support the new gyro, magnetometer and the addition of the barometric pressure sensor. Also, we have a Windows GUI for showing all the sensor data as well as attitude and heading in real time.


  • ADXL345 – triple axis accelerometer (I2C)
  • ITG-3200 – triple axis gyro (I2C)
  • HMC5883L – triple axis magnetometer (I2C)
  • BMP085 – barometric pressure sensor/temp sensor (I2C)

Some of the features:

  • Complete inertial measurement system measures linear acceleration, angular velocity, and magnetic heading
  • Calculate altitude using the barometer
  • Temperature sensors built into the barometer and gyro
  • All sensor data is processed by the onboard Atmega328P and output to your computer or micro over the serial port
  • Preloaded with Arduino bootloader (select “Arduino Pro or Pro mini (3.3V, 8MHz) w/ Atmega328”)
  • All headers and mounting holes are on a 0.1″ grid to allow mounting to a protoshield or standard perf board
  • 9 user IO pins brought out to header. Add buttons, LEDs, servos, GPS…
  • I2C header for debugging or adding additional I2C sensors
  • On board power and status LEDs
  • On board 3.3v regulator allows powering from a single Lipo battery
  • small 1.6″ x 1.1″

We have the first batch assembled and tested. I’ll post a link when we get the store turned on.