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Balancing robot – without gyros

Posted by Mike Redrobe | Posted in Arduino, robots | Posted on 25-05-2012

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Bot balancing without gyros … for a few seconds at least

No gyros, no accelerometers – only a sonar ranger and lots of code.

The motors used are standard servos modified for continuous rotation, sonar sensor is a HC-SR04 as detailed in a previous post

Code ? Well here’s a simplified portion of the PID loop:

    int Drive = 0; // PWM value sent to Servos
    int Error[5]; // array of 5 Error elements
    int P = 0; // proportional term
    int I = 0; // integral term
    int D = 0; // derivative term

    #define Current 0
    #define Sum 1
    #define Last 2
    #define SecondToLast 3
    #define Delta 4

    int PID() {
    Error[Current] = SetPoint – Ptime;
    P = Error[Current] * Kp;
    Error[Sum] = Error[Current] + Error[Last] + Error[SecondToLast];
    I = Error[Sum] * Ki;
    Error[Delta] = Error[Current] – Error[Last];
    D = Error[Delta] * Kd;
    Drive = P + I + D;
    Error[SecondToLast] = Error[Last];
    Error[Last] = Error[Current];

    return Drive;
    }

Ultrasonic robot avoids walls

Posted by Mike Redrobe | Posted in Arduino | Posted on 21-05-2012

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Using an ultrasonic sonar ranger to avoid walls – and people’s feet – before hitting them:

At first I was getting plenty of false readings, so here’s the first run, pausing and verifying before turning:

With faster code, and not stopping:

Improved accuracy, so it detects smaller objects like feet:

Arduino and SR04 ultrasonic sensor – robot eyes !

Posted by Mike Redrobe | Posted in Arduino | Posted on 20-05-2012

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Hooked an SR04 ultrasonic sensor to my arduino board – robot eyes !

Ranger sensor uses sonar to give accurate distance measurement to objects or obstacles placed in front of it. They’re surprisingly sensitive / accurate – I was able to reliably measure to a millimeter at 15cm range.

These sensors are also now VERY cheap £2.37 (4$) delivered from HK, and accurate to a few mm.

Added a servo for visual feedback:

Arduino code is basically sending a trigger on one pin, receiving a timing value on another,
which can then be converted into a distance:

    pinMode(TP,OUTPUT);
    pinMode(EP,INPUT);
    Trig_pin=TP;
    Echo_pin=EP;

    digitalWrite(Trig_pin, LOW);
    delayMicroseconds(2);
    digitalWrite(Trig_pin, HIGH);
    delayMicroseconds(10);
    digitalWrite(Trig_pin, LOW);
    duration = pulseIn(Echo_pin,HIGH);

BBC News add-ons for firefox and chrome

Posted by Mike Redrobe | Posted in browser add-ons, Software | Posted on 17-05-2012

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Following on from my recent add-ons, here’s a handy plug-in to display latest bbc news headlines.

Instead of opening a tab, this opens a faster mini window on a single click:

So go get the add-on “Latest BBC News” for both firefox and chrome:

V 1.0

Features

  • Get all the Latest BBC News headlines with a single click.
  • Opens a popup widget with the latest news headlines.
  • Links at the bottom to show all sections:
    Technology, Health, Entertainment etc

 

Get it yourself direct from:


BBC News for Firefox

and for chrome:

BBC News for Chrome
Youtube video

Hot UK Deals – add-ons for firefox and chrome

Posted by Mike Redrobe | Posted in browser add-ons, Software | Posted on 10-05-2012

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An avid bargain hunter, I often keep an eye on HotUKDeals.com for the latest deals,
and following on from my recent add-on for ebuyer’s website, I thought I’d make a more convenient way of checking the site.

Instead of opening a tab, this opens a faster mini version of the site on a single click:

It also adds the oft-requested feature of page numbers at the top of threads on the main site:

 

Much better !

So go get the add-on “Top UK Deals” for both firefox and chrome:

V 1.1.0

Features

  • Opens a fully functional small version of the HUKD website
  • You can
    – sort by date,
    – sort by recently comments

    – view/post comments

  • You can even post a new deal direct from the popup !
  • Also makes minor edits to the main HotUKDeals site :
  • – adds pagination box to the top of the comments page [ 1.,2.3…last]

 

Get it yourself direct from:


Top UK Deals for Firefox

and for chrome:

Top UK Deals for Chrome
Youtube video