Sunday, 26 May 2013

Receiving From The Stars. Radio Astronomy Station Part 3.

Assembling the Radio Hardware
I thought in this post I would concentrate on the computer side of the Radio Telescope. Many of the parts can readily be assembled and tested without too much mechanical work, in fact none at all.
We'll need our SDR USB stick that we bought on Ebay, our Raspberry Pi and a PC running Windows 7 (you may find it best to use a laptop or PC with an SD card slot that works properly with an SDHC High Capacity 8GB card).

For the benefit of those that might not be computer savvy I've gone into some detail in explaining how to install software in the Raspberry Pi. As this is the important part of the whole system it seems worth it to explain as much as I can.

Step 1. Setting up your Raspberry Pi.
Lets assume you have your new Raspberry Pi in its box. Its just arrived in the mail and you can't wait to see what it does. Mine came from RS Components in a raspberry colored plastic box and packed inside an antistatic bag.

You'll need a good quality 8 or 16GB SD card for your Raspberry Pi operating system. Some laptops come with SD card slots in them. Note that older laptops may not be able to use SD cards larger than 4GB. If yours is one of those then you can still fit everything into a 4GB card (just).

On your laptop head to http://www.raspberrypi.org and select the 'Downloads' link at the top of the page. Select the first option Raspbian Wheezy (direct download) which is probably best for our purposes and save to your laptop Desktop. This is currently a 470MB download so make sure you have a decent internet connection. Note that the download page has options for choosing a mirror site that may be closer to your location and may result in a faster download.

While you are downloading your copy of Raspbian Wheezy, go and get a copy of 'Win32DiskImager' http://sourceforge.net/projects/win32diskimager/ as we need this to write to our SD card. Save the zip file for DiskImager (Windows may pop up a request bar asking if you want to download it). The DiskImager is only 5.7 MB so while we wait for Raspbian, right click on the win32DiskImager.zip file and open it. Extract it to the suggested folder. You should now have a new folder on your desktop with DiskImager files in it.

Once you have the Raspbian ZIP file on your desktop extract the folder inside the zip file by right-clicking and choose 'Extract Here'. The file in the download is an IMG file. This 'Image' file is intended to be written or 'burned' to a CD. For our purposes we need to instead write it to our SD card.
On your Windows PC desktop open the 'Computer' or 'MyComputer' icon. If you have your SD card plugged in it will show in this window. Double click the SD card. Some new cards come with 'Extras' in them. Delete all files on the SD card.

Open your DiskImager folder and start Win32DiskImager.exe.
Select your Raspbian Wheezy IMG file and select the SD card with the 'Device' selector. This will probably show up as E:/ or similar. Click on 'Write' and your Raspbian Wheezy Image file should be written to the SD card. The SD card is your 'Hard Drive' for your Raspberry Pi. When your Image is finished being written close DiskImager and eject the SD correctly by right clicking on the SD card in My Computer and selecting 'Eject'. This will close the SD card so files don't get corrupted.

Step 2. Starting your Raspberry Pi.
We now have our Raspberry Pi board and an SD Card with Raspbian Wheezy on it. Fit your SD card and connect a screen to either the Composite Video RCA socket or the HDMI Video port. Plug in a USB Keyboard and Mouse to the two Raspberry Pi USB sockets. Connect an Ethernet cable from the Raspberry Pi to a spare port on your Network Router.

A few points about power supplies. The Raspberry Pi is designed with a Micro USB (mobile phone standard) power connector. If you have a Phone charger just check that the charger will deliver at least 1 amp. Some will only supply 700mA which will probably not be enough. I use a Nokia charger that has 1200mA @ 5V written on it and seems to work well.

Connect your power supply. Fingers crossed and the red PWR led on the Raspberry Pi should light up followed a few seconds later by the other Leds. Your LCD screen should come up with the Raspberry Pi logo followed by a screen full of startup information. Eventually the 'Raspi-Config' window should open giving you several setup options. They are pretty self explanatory. When finished tab to Finish and the Pi should restart.
The default user name is 'pi' and the default password is 'raspberry'. This should be changeable in the Raspi-Config setup program.

Once you log in, type in 'startx' and the Raspberry Pi desktop should start up. Now the fun starts.
But I will save that for the next post.

If you have any issues with the above, look around and Google some answers. I'm happy to answer any queries at the end of this post.

Cheers.