Monthly Archives: May 2013

Uncategorized

Pi powered Panobot v1

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I have just finshed work on version 1 of my Pi powered Panobot. It is a robot designed to take panoramas with the official raspberry pi camera board.

It is built out of lego and uses the same motors and motor controller as my Lego Pibot.

It runs a python script which allows me to program how wide a panorama I want and how many levels. Once the images are taken I copy them over to my laptop and stitch them together into one image using Hugin http://hugin.sourceforge.net/

The Pi camera is very good for its price but compared to my DSLR has a smaller dynamic range and also a smaller HFOV (Horizontal Field Of View) so to get a panorama, it requires a few more pictures. I found to allow enough overlap that 10 pictures wide was sufficient by 3 pictures tall. This totaled to 30 pictures per panorama compared to my normal 25 pictures for my DSLR. I have to stitch them on my laptop instead of the pi due to massive amount of processing power to find the control points

So, time for some pictures

The panobot on a hedge taking some pictures
The panobot on a hedge taking some pictures
A closer look inside the panobot
A closer look inside the panobot

Now for what you have been waiting for, what images does it produce?

180 Degree panorama

A full 360 degree panorama shot with the Raspberry Pi camera board
A full 360 degree panorama shot with the Raspberry Pi camera board

For the full sized panobot panorama click here as wordpress limits the upload size

A panorama taken from the same area with my DSLR (Canon 600d)
A panorama taken from the same area with my DSLR (Canon 600d)

For the full sized DSLR panorama click here as wordpress limits the upload size

280 degree panorama taken in the evening before batteries died
280 degree panorama taken in the evening before batteries died

For the full sized  panorama click here as wordpress limits the upload size

Full 360 degree panorama made up of just 30 pictures!
Full 360 degree panorama made up of just 30 pictures!

For the full sized  panorama click here as wordpress limits the upload size

For the full sized  panorama click here as wordpress limits the upload size

 

As you can see, there really isn’t much in it between the DSLR and the Raspberry Pi Panobot. There is two thing though to take into account though.

Time

The Panobot takes around 2 mins to complete a full panorama

Using the DSLR I took the example panorama in under 30 seconds

Stitching

Because of the larger HFOV on my 28mm lens on my DSLR, I only took 24 photos for the full panorama (In portrait mode to reduce lens distortion). 24 photos takes about 3-4 mins to stitch

The Pi camera board took 30 pictures to get a full panorama. It took 4 mins to stitch those though.

So there is definitely trade off with using a completely automated pi camera but I am still quite pleased with the results. It was a great learning experience and a great option for someone who can’t afford a larger camera, the whole system (excluding lego) runs in about £50-£60

A copy of the python code can be found here

A copy of the python code on github can be found here

Pibot, Raspberry Pi

Lego Pibot Ultrasonic wall avoider

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I have been working on getting the cheap ultrasonic sensor working for the past week and have got it working with my Lego Pibot.

It sends out an ultrasonic blip every 0.1 seconds and measures the time it takes for it to get a bouce back.

I followed a very helpful guide at raspberry spy which I got a lot of the ideas from.

http://www.raspberrypi-spy.co.uk/2012/12/ultrasonic-distance-measurement-using-python-part-1/

Camera board, Pibot, Raspberry Pi, Uncategorized

Raspberry Pi camera board – Gstreamer

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So, my Raspberry Pi camera board has arrived and I have started playing with it.

Raspberry Pi camera board

My first impressions were tiny, super cheap camera. Its low light capabilities are not great but I can live with that. The important bit is the quality, full 1080p at 25 frames per second (UK). That on its own is pritty awesome.

I was though only really interested in getting the pi to work remotely for my robot to replace the 3-4 fps standard def USB webcam I currently use. Currently though with the camera, there is no V4L driver so we have to make do with their provided applications then pipe it out to streaming applications. Their recommended method is slow and very laggy (netcat and mplayer with wifi provides 3-6 seconds of lag). So I had to find another option. I happened to be sitting on the #raspberrypi IRC on freenode and heard a user having success with gstreamer. So this is how to set up gstreamer to stream HD video with less than 0.5 seconds of lag.

First we need to add a repositary with gstreamer1.0

 

sudo nano /etc/apt/sources.list

 

and add to the end

 

deb http://vontaene.de/raspbian-updates/ . main

 

Then do an sudo apt-get update

next grab gstreamer

 

sudo apt-get install gstreamer1.0

 

 

On your recieving end you will also need gstreamer. Because I mainly use a mac, I decided to get it working on the mac so with help from arcanescu on IRC, we figured out how to get it working on mac os (10.8)

The simplest way is with brew, a package manager like apt-get, but for mac os. To install it run this in terminal on your mac simply run

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

It will grab and install brew. Now update it with

 

brew update

 

Now we need to grab gstreamer

 

 brew install gstreamer gst-libav gst-plugins-ugly gst-plugins-base gst-plugins-bad gst-plugins-good

 

Once that installs you should be good to go. Enter

 

 raspivid -t 999999 -h 720 -w 1080 -fps 25 -hf -b 2000000 -o - | gst-launch-1.0 -v fdsrc ! h264parse !  rtph264pay config-interval=1 pt=96 ! gdppay ! tcpserversink host=YOUR-PI-IP-ADDRESS port=5000

 

on your raspberry pi and enter on your mac

 

 gst-launch-1.0 -v tcpclientsrc host=YOUR-PI-IP-ADDRESS port=5000  ! gdpdepay !  rtph264depay ! avdec_h264 ! videoconvert ! autovideosink sync=false

 

The picture quality is good but I see a number of flickers which isnt a problem for me, if it is for you, maybe try adjusting the resolution

 

So thanks again to arcanescu, I take no credit for this as it was him that came up with this, if you ever see him in IRC, give him a virtual pat on the back

His blog garagedeveloper.wordpress.com