This category contains 35 posts


The BNO055 IMU or Intelligent 9-axis absolute orientation sensor as Bosch like to call it is a sensor that combines a 3 axis gyro, accelerometer and magnetometer in a single small package. In many respects this makes it similar to products like the Mindsensors AbsoluteIMU and the Dexter Industries dIMU, however the BNO055 has two features which … Continue reading

Line following with openCV

In a previous article I built a simple line following robot. I had intended to follow this article up with more about building cooperating systems, but I’m afraid I got distracted! In particular I spent some time adding openCV (the open source image processing project) to leJOS. As a result I wanted a project to explore what … Continue reading

Publishing data to MQTT

The MQTT message broker is very popular for publishing sensor data for Internet of Things (IoT) devices. This post shows you how to publish EV3 sensor data to it. The image above shows a flow that subscribes to the sensor data topic and prints it out using the very popular node-red visual web tool. To … Continue reading

openCV web streaming

This post is a start of a series on using openCV with leJOS robots controlled from Android phones. openCV is supported in the latest snapshot of leJOS and will be supported in the next release, which is coming soon. I will start off with a version of my Webcam HTTP streaming code. This uses openCV … Continue reading

EV3 to EV3: Running text. Take two!

In the previous article we saw how things don’t always go to plan when trying to put together demos. In this post I want to describe an alternative approach to the same problem (creating a running text display over linked EV3s) that works. The standard leJOS remote API basically provides a way to access the … Continue reading

EV3 to EV3: Running text. Sometimes things don’t work!

  When I first started planning this series I wanted some easy to describe simple examples of using multiple EV3s together to demonstrate the various leJOS APIs. One of the first examples I came up with was that of a running text display. I wanted to place the EV3s next to each other and have … Continue reading

PAN, the leJOS answer to daisy chaining

Andy wrote a series of articles about connecting multiple EV3’s and how to get them to work in a coordinated way. This exciting new feature will become available in the next (post 0.9.0-beta) release of leJOS. Make sure you are prepared, read the articles and start saving for your next EV3. Continue reading

EV3 to EV3: Motor control

In the previous article we saw how leJOS can be used to control the LEDs on remote EV3s, but what about motors? Can the same technique be used for those? Let’s take a look. Like before we are using 4 EV3s all connected together in a PAN using Bluetooth, this time each EV3 has two … Continue reading

EV3 to EV3: Using remote methods

In previous posts we have looked at how we can connect multiple EV3s together into a PAN (Personal Area Network), in this article we will see how we can use the PAN to allow us to write a simple program to control the resources of one EV3 from another. There are several ways to create this … Continue reading

Webcam HTTP streaming

To follow up my post on webcam streaming, here is an example of HTTP MJPG streaming. This allows you to open the stream in a browser using a URL like However, Chrome does not let you open this directly – it must be embedded in an HTML document, e.g.: Here is the EV3 code, … Continue reading

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