IEEE Spectrum

IEEE Spectrum


Who Needs Real Friends When Robots Will Play Nintendo With You

Posted: 05 Aug 2015 01:27 PM PDT



Japanese researchers teach a little humanoid how to play Wii tennis

Simple Device Could Convert DC Electric Field To Terahertz Radiation

Posted: 05 Aug 2015 01:00 PM PDT



Physicists propose a simple device design that emits tunable THz radiation when a DC current passes through it

Google Asks France Not to Require Global Right To Be Forgotten

Posted: 05 Aug 2015 10:15 AM PDT



Search giant says French data agency order goes too far

A New Spin on Silicon

Posted: 05 Aug 2015 09:00 AM PDT



Photon spin determines direction of current in silicon device

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Interfacing a Load Cell With an Arduino Board

General Specifications

Over the years, many RobotShop customers have asked us about the easiest way to interface a load cell with an Arduino board so they can get accurate weight measurements. Instruments like load cells provide small signal values and need to be amplified for processing, so without additional electronics, these sensors cannot and should not be connected directly to an Arduino’s I/O pins. Arduino boards like the UNO have a 10 bit ADC, which means that the resolution of the analog input pins are 5V/1024 ≈ 4.9mV. For this reason, variations less than 4.9mV will not be recognized by the Arduino board without the appropriate amplification and filtering. The two common approaches for interfacing a load cell with an Arduino are :

  • Amplifying the load cell’s output voltage signal (using a pre-packaged instrumentation amplifier IC like the INA125 to be processed by the Arduino’s ADC).
  • Using a High-resolution ADC which can be interfaced with the Arduino.

Luckily, there is a new option for those seeking a plug and play solution to avoid extra wiring and coding: the Strain Gauge / Load Cell Amplifier Shield. This board makes interfacing an Arduino and an instrumentation amplifier significantly easier. This stackable shield can be used with various low output sensors like load cells. It’s a low cost solution for precise amplification of measurements especially for robotics, multichannel systems, medical instrumentation, industrial process control and more.

The Load Cell Shield features an AD8426 dual channel Instrumentation amplifier. The gain produced by the AD8426 amplifier ranges from 1 to 1000 depending on the GAIN resistor value. The output voltage reference of each channel can be adjusted with the two onboard potentiometers. The shield has also a low-pass 2nd order Bessel filter at 1000Hz for both channels.

strain gauge load cell shield

Strain Gauge / Load Cell Shield

 

Setup and Wiring

A load cell usually has 4 wires, but it’s important to check the wiring for the unit you have:

  • Red Wire: Excitation +
  • Black Wire: Excitation –
  • Green Wire: Signal +
  • White Wire: Signal –
5 kg micro load cell

5 kg Micro Load Cell

The parts needed for connecting the load cell to the shield :

parts needed

Parts Needed

Solder the F/F jumper wires to the Load Cell wires. To avoid mixing the wires when connecting the load cell, you can choose the same color wires as those of the load cell :

sodering load cell with jumper wires

Soldering

Add heat shrink over the soldered areas:

putting heat shrink

Heat Shrink

Connect the load cell to the Load Cell Amplifier Shield:

connecting load cell to the shield

Connecting the Load cell

Stack the Load Cell Amplifier Shield on top of the Arduino board (in our case, a Lynxmotion BotBoarduino):

stacking the load cell amplifier shield to the arduino board

Stacking the Load Cell Shield

The Load Cell Shield uses analog pins A0 and A1 for Strain 1 and Strain 2 inputs respectively. The white connectors on the board are 4 pin Molex connectors with 0.1″ spacing. There are two modifications per channel that can be done to adjust the output voltage of the shield described below:

Gain

The gain of the amplification per channel is dependent on the Gain1 / Gain2 resistors. The AD8426 default gain is 1 without a gain resistor. The standard gain resistor value of the shield is 100 Ohm (for each channel) for a gain of 495. These resistors can be replaced depending on the user’s application with the appropriate ones. The gain can be calculated by using the following gain equation (from AD8426 datasheet) : Rgain= 49400/(Gain-1)

strain gauge load cell amplifier shield gain

Amplifier Gain Resistor

Reference voltage

The reference voltage feature is used to offset the output signal to a mid-supply voltage to be used with a single power supply ADC. The reference voltage can be set using the onboard potentiometers associated with each channel.

strain gauge load cell amplifier shield gain reference voltage

Channel 1 and 2 Reference Voltage

Arduino Sample Code

This Arduino Sample Code reads analog pin 0 (Strain 1) and analog pin 1 (Strain 2) so that the load cells can be calibrated by linear interpolation.

     
 
 
   
   

Trossen Robotics Blog

Trossen Robotics Blog

Link to Trossen Robotics Blog

Marquette University’s HEIR Lab Participates in RoboCup

Posted: 05 Aug 2015 08:40 AM PDT

MU-L8

HEIR Lab (Humanoid Engineering & Intelligent Robotics), at Marquette University took their robot to RoboCup 2015 in Hefei, China! The team is lead by Andrew B. Williams, Ph.D., who has written up a fantastic post on the subject.

This week, our students in the Marquette University Humanoid Engineering & Intelligent Robotics (HEIR) Lab are participating in perhaps the largest and the oldest robot hackathon in the world, RoboCup, in Hefei, China. RoboCup is sometimes referred to as the World Cup of robotics and artificial intelligence. This is the tenth anniversary since I founded and led the Spelman College SpelBots to our first RoboCup in Osaka, Japan and it is a privilege to lead our current, outstanding team from Marquette University College of Engineering: Matt, Adrianna, Ryan, and Sally.

For the rest of the post, check out his blog, and make sure to watch their Qualification video from RoboCup 2014 below!

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DFRobotShop Rover Tutorial – Control With Android App / Bluetooth

DFRobotShop Rover - Title 3_25

DFRobotShop Rover v2 (Bluetooth Kit) [RB-Rbo-41]

The DFRobotShop Rover products have been out for a while and we have received many questions since then on both our support center and on our forum. One common question we get is how to control the rover using a smart phone / tablet?. This tutorial will cover a simple Android-based solution to make this happen for you and your rover!

Requirements

Please note there is also a DFRobotShop Rover v2 Bluetooth Kit with the Bluetooth module and a LiPo battery included, which is perfect for this application.

Programming the Rover

You can download the code for the Rover v2 here. Extract the files to a folder and go into the folder named “tank_wasd_keyboard_control“. From there, open the .ino file. If you have the Arduino IDE installed, it should automatically open the file. Make sure your rover is connect via USB to the computer and that you have the proper Arduino Uno drivers installed. Go to the Tools menu in the Arduino IDE and ensure you have the right board (Arduino Uno) and the right COM port selected.

Make sure to remove the DFRobot Serial Bluetooth Module before uploading code to the rover. Click the Upload button and wait for the process to finish. Once the upload is complete, you can optionally use the Serial Monitor (from the Tools menu or using the top-right corner icon Serial Monitor Icon) to test the rover. Make sure to select a baud rate of 9600. Send ‘W‘, ‘S‘, ‘A‘, ‘D‘ to move the rover forward, backwards, turn left and turn right. Send any other key to make the rover stop moving.

Once you are done uploading / testing the rover, simply disconnect the USB cable and replace the DFRobot Serial Bluetooth Module on its socket.

Bluetooth Pairing

Android Bluetooth Settings

From your Android device home screen, open Settings. Go to the Bluetooth category. Make sure the rover has the Bluetooth module on and that the Rover is powered. Also make sure the Android device’s Bluetooth interface is ON. If the device does not show up in the list press “Search for devices” and wait for it to show up. It should be named “Bluetooth_Bee_V2“. Select this device to start the pairing process.

blue-02-s

Bluetooth Pairing

To pair the device, you will need to enter the PIN 1234. Once this is done the module will pair to your Android device. It should now show up in the list under the heading “Paired devices“, as seen below.

blue-03-s

Module Paired

Obtaining the App

You can obtain the free app here. Note that this app is not affiliated with RobotShop. If you are unable to to use this link, please follow these steps to obtain the app:

app-1-s

Google Play – Apps

First, open the Google Play app. From there, go to the “Apps” category.

app-2-s

Google Play – Arduino Bluetooth Controller

Then, search for “Arduino Bluetooth Controller“. Press on the app showed above.

app-3-s

App Installation

Install the app by pressing the “Install” button

app-4-s

Opening the App

Finally, once the app is installed press “Open” to start the Arduino Bluetooth Controller. Before opening the app, make sure the rover is still powered with the Bluetooth module attached and that the pairing was completed successfully.

Using the App

use-1-s

Bluetooth Permission Request

When the app starts, it may request that the Bluetooth to be turned on (if it was previously off). Activate Bluetooth to make sure we can connect to the rover.

use-2-s

UUID

Next, the app will ask you if you wish to change the UUID. There is no need to change it, so simply press “Proceed” to continue.

use-3-s

Bluetooth Paired Devices

Select the paired device called “Bluetooth_Bee_V2“. If it is not visible, ensure the rover is powered and the Bluetooth module is attached and press “Scan for devices“. If the device still doesn’t show up, go back to the Bluetooth Pairing step.

use-4-s

Controller Mode

Once at the mains screen, select “Controller Mode“. The view below is what is visible on a larger tablet screen. When viewed on a smart phone, the buttons will be closer together.

use-5-s

Set Commands

From the controller screen, select options at the top right and choose “Set Commands“.

use-6-s

Commands

Press each button name and enter the command of your choice. The default commands in the “tank_wasd_keyboard_control” example are ‘W‘, ‘S‘, ‘A‘, ‘D‘ as mentioned previously. Here we chose ‘X‘ as the “stop” command. When done setting the commands, press the back arrow to return to the controller screen.

You can now press the buttons on the screen to control your rover remotely through Bluetooth! Enjoy!