Wednesday
May152013
Weekend Project: PiSwitch using the Raspberry PiFace
Wednesday, May 15, 2013 at 10:54AM Here at Polyideas we're big fans of power efficiency- we're convinced it's the next big thing. Some people may hear 'efficiency' and think going without- but more and more these days there are clever solutions to saving electricity. In Southern California, this means saving money!
This project focuses on a common area of power usage in the home- the humble PC. Sure, laptops are more efficient- but sometimes only a PC will do. Many of us leave a PC on just in case we need to log onto it remotely. If we're not using it, it's just sitting there using electricity- and usually quite a bit of it. The most efficient desktop PCs still use around 35-45 watts when idling. Gaming PCs with big video cards can easily top 200 watts!
The PiSwitch solution lets you hook up a Raspberry Pi to your PC to control your power and reset buttons. The Raspberry Pi only uses about 1 watt of power when on, so it's more economical to leave it on all the time. In this article, I'll walk through how to set up the Raspberry Pi from start to finish to do this. The list of parts is available below, most of which you can get from SparkFun. All Sparkfun parts are on the wishlist here.
- Raspberry Pi
- Raspberry PiFace expansion card
- SD Card
- 5V power supply
- Micro USB cable
- Stand off screws
- Stand off spacers
- Motherboard wires
- 3.5" Hard drive adapter tray (I used the free tray that came with my Intel SSD)
This project makes use of the very nifty Raspberry PiFace, which takes all the guesswork out of interfacing switches with the Raspberry Pi. In this article, we'll do the following:
- Format the SD card with Raspbian Wheezy
- Install the files needed for the PiFace
- Setup our scripts
- Install the Raspberry Pi in our PC case
- Test it out
If you're familiar with our last Raspberry Pi article on setting up the MiniDLNA server, these steps may be familiar- this time we're using Raspbian Wheezy (http://www.raspberrypi.org/downloads). Other than that, these next few steps cover imaging your SD card using a PC. We're a pretty PC-friendly shop, so here we go! These steps work the same on Windows 7 & 8. MAKE SURE YOUR SD CARD IS EMPTY- we will be erasing it in the next few steps!
Right-click on the new hard drive and select 'Format'. Be very careful you've got the right drive!
If the memory card is under 20GB, select FAT32. Others might work, but I have done this with FAT32. That's ok, because it's going to get overwritten. We need the SDHC card to be blank though- don't skip this step.
If the memory card is under 20GB, select FAT32. Others might work, but I have done this with FAT32. That's ok, because it's going to get overwritten. We need the SDHC card to be blank though- don't skip this step.
Go ahead and check the box 'Quick Format' and click the 'Format' button.
Now that we have a blank SDHC card, we can write the Wheezy image onto it!
Download a copy of the Raspbian Wheezy 2013-02-09 image from here. This may take a little bit since it's over 800 megabytes, so we'll come back to this step in a bit. When it's done downloading, it's a zip file that must be extracted to get the file named "2013-02-09-wheezy-raspbian.img".
Download the Win32DiskImager application here and extract the zip file to a folder. Inside the folder of files you just extracted, you will find Win32DiskImager.exe, go ahead and run it. If you're on Windows 7 or 8 and have User Account Control (UAC) turned on, it may prompt you for administrator access- this is ok since the application needs access to your disk devices to write the image. Now that we have it running, it looks something like the window below:
Click the blue file icon and navigate to your 2013-02-09-wheezy-raspbian.img file. If you try to do it with the original zip file you downloaded without extracting it, this process won't work. Under 'Device' you'll see that the application has selected a removable disk letter for you automatically. Make sure this is the right drive letter for your SDHC memory card! Again, if you select the wrong drive letter you can erase a drive on your PC. Once you're sure, click the "Write" button.
Click the blue file icon and navigate to your 2013-02-09-wheezy-raspbian.img file. If you try to do it with the original zip file you downloaded without extracting it, this process won't work. Under 'Device' you'll see that the application has selected a removable disk letter for you automatically. Make sure this is the right drive letter for your SDHC memory card! Again, if you select the wrong drive letter you can erase a drive on your PC. Once you're sure, click the "Write" button.
When it's done you'll get a dialog box that tells you it's been successful. This means you have successfully written the Wheezy image to the SDHC card. Go ahead and unplug the SDHC USB adapter from your computer and insert it into the Raspberry Pi. Note the angled end of the memory card and how it lines up with the Raspberry Pi when you slide it in.
Go ahead and hook up all the connections to the Raspberry Pi. We're going to need to connect a monitor to it for the first time while we setup networking and some other steps. Go ahead and plug in an HDMI monitor, a USB keyboard and an ethernet cable. You may be able to use WiFi for this project, but our PC case is all metal and the wireless signals will have trouble- so this article will focus on wired networking.
Go ahead and connect the power, which will power on the Raspberry Pi. Run through the local menu that you get the first time to change your locale and keyboard layout among others. The UK keyboard is the default, and if you leave it in place you will have trouble using the '#' key. Make sure to go through each line in the initial setup. If you forget to do something like change your keyboard layout or expand the SD card, you can come back to the first setup menu by running 'raspi-config' from the command prompt.
After you've setup the initial settings, we still have a few steps to perform. We need to setup networking, update the Raspberry Pi and install the files for the PiFace. First, let's set a static IP address for the Raspberry Pi. This will make it easier for us to remote into the Raspberry Pi from other machines, and it's required if we're going to open a port on our router to get to the Raspberry Pi. Let's
start by running the command:
sudo nano
/etc/network/interfaces
We need to comment out a couple lines on the configuration- when we add a '#' to the beginning of a line, it tells Linux to skip that line- this lets us disable certain lines without deleting them.
The file starts out looking like this:
auto lo
iface lo inet loopback
iface eth0 inet dhcp
allow-hotplug wlan0
iface wlan0 inet manual
wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
iface default inet dhcp
When we're done, we've added our static IP, network mask and default gateway. Don't forget to make sure your Raspberry Pi's static IP doesn't overlap with ones given out by your router. My final network setup looks like this:
auto lo
iface lo inet loopback
#iface eth0 inet dhcp
iface eth0 inet static
address 192.168.123.123
netmask 255.255.255.0
gateway 192.168.123.1
allow-hotplug wlan0
iface wlan0 inet manual
wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
iface default inet dhcp
The easiest thing to do now is save the file with a Ctrl-O then quit with a Ctrl-X. Now reboot with the command:
sudo reboot
When the Raspberry Pi comes back, go ahead and login. Try pinging www.yahoo.com with the command:
ping www.yahoo.com
You should see ping times in milliseconds if your network setup is good. If not, you'll need to grab a networking friend to help you get your networking squared away. Assuming we're good here- let's update some hardware settings our Raspberry Pi. We do this with the following commands:
sudo nano /etc/modprobe.d/raspi-blacklist.conf
When it's open, insert a # at the start of the line that says 'blacklist spi-bcm2708'. The line should now look like this:
#blacklist spi-bcm2708
Now save the file with a Ctrl-O then quit with a Ctrl-X. Now when the Raspberry Pi reboots it will find the PiFace automatically. From the shell we can run this command to turn it on manually:
sudo modprobe spi-bcm2708
Now that our PiFace hardware is setup, let's update the software to use it. Run the following commands to update your Raspberry Pi:
sudo apt-get update
sudo apt-get upgrade
If you are prompted, press 'Y' or enter to agree to the updates. The second command will take a little while, so it's a good time to grab a cup of coffee. When these commands have completed, run the following command:
wget -O - http://pi.cs.man.ac.uk/download/install.txt | bash
This step installs the files needed for your PiFace. When it's done, shut down with Raspberry Pi with the command:
sudo halt
After all the green and yellow lights are off on your Raspberry Pi, go ahead and unplug all the connections. We need to drill the holes into the mounting plate so we can install the Raspberry Pi inside our PC case. You can see in the photo I have a wifi adapter on my Raspberry Pi to make sure I have room to add the wifi later if I want.
I used a small jewelers screwdriver (link) to scratch two small holes on the bracket to line up with the mounting holes on my Pi. Next, I drilled the holes- the holes need to be slightly larger than the thread in the screws.
After the holes have been drilled, I add in my spacers and spacer screws, if you look close you can see them in the pic below:
After we install the spacers, we can mount the Pi to the spacers, then the PiFace to the Pi. It should look something like this:
Now let's take our motherboard wires and clip the ends with the switches off. Clip close to the switches to make sure we have as much length of wire as possible- it needs to be able to reach our motherboard after we install the Pi. After we clip the switches off the wires, let's strip 1/8" of wire off the ends we just clipped. Attach the wire pair for the reset switch to terminals closest to jumper #3 on the PiFace.
Make sure the wires go in the center connector and the 'NO' connector. This means 'Normally Open' and means the switch is off unless you turn on the relay.
Attach the wire pair for the power switch to terminals remaining relay terminals, again using the center connector and the 'NO' connector.
When we're done, our setup should look like this:
Now that we've connected the wires, let's power on our Raspberry Pi to test the setup before we install it in the PC. Reconnect everything on the Raspberry Pi and login. Let's create our script files for power on and reset of the PC. Let's start with the reset. Run the command:
nano reset.py
The Nano text editor opens, type or paste in this:
#!/usr/bin/python
from time import sleep
import piface.pfio as pfio
pfio.init()
pfio.digital_write(0,1) #turn on
sleep(0.1)
pfio.digital_write(0,0) #turn off
exit()
from time import sleep
import piface.pfio as pfio
pfio.init()
pfio.digital_write(0,1) #turn on
sleep(0.1)
pfio.digital_write(0,0) #turn off
exit()
Now save the file with a Ctrl-O then quit with a Ctrl-X. Now we need to mark the file as executable to make it easier to run. Run the command:
chmod +x reset.py
Now you should be able to run this command and hear the PiFace quickly click one of its relays, just like a person hitting the reset switch on a PC when you run the command:
./reset.py
If you're looking at the PiFace you can see an LED flash on as well. Run it as many times as you like to test. When you're done, let's make the power script by running the command:
nano power.py
The Nano text editor opens, type or paste in this:
#!/usr/bin/python
from time import sleep
import piface.pfio as pfio
pfio.init()
pfio.digital_write(1,1) #turn on
sleep(0.1)
pfio.digital_write(1,0) #turn off
exit()
from time import sleep
import piface.pfio as pfio
pfio.init()
pfio.digital_write(1,1) #turn on
sleep(0.1)
pfio.digital_write(1,0) #turn off
exit()
Now save the file with a Ctrl-O then quit with a Ctrl-X. Now we need to mark the file as executable to make it easier to run. Run the command:
chmod +x power.py
Now you should be able to run this command and hear the PiFace quickly click one of its relays, just like a person hitting the power switch on a PC when you run the command:
./power.py
If both of these run fine, then you're ready to power off and install the PiSwitch in your PC case. If you get errors, you need to recheck our PiFace hardware setup from the commands to make sure the hardware has been found. Also, remember that these Python scripts are sensitive to formatting, so extra tabs or spaces will break the scripts. Go ahead and shut down the Pi with the command:
sudo halt
Unplug the power, usb keyboard and network connections and install the PiSwitch in the PC case. You can see how I ran the power and network cables through the back of my PC case here:
Unplug your PC case's connectors for your power and reset wires from the PC motherboard and replace them with the PiSwitch ones. If you want to be fancy you can splice the PiSwitch ones without unplugging the existing case ones, but for us we'll just wire the PiSwitch directly to the motherboard. You can see this in the photo below:
When we're all wired up, go ahead and power on the Raspberry Pi, making sure the power and network cables are plugged in. Then from your PC you can remote into your Pi using SSH (we like Putty). Go ahead and test the power on script by running:
./power.sh
You should see your PC power on! If you don't, try running:
./reset.sh
If that works, it means you have your power and reset wires mixed up. Now you're ready to remotely turn your PC on and off remotely! We'd like to thank our sponsor Sparkfun for their support.
