birds like wires

Showing 'energy' tagged articles.

Saving Power with your ATmega

http://www.flickr.com/photos/soujirou/4651611953/

As many projects using an MCU end up running from batteries, it’s nice to have those batteries last as long as possible. There are a numerous different ways of doing this, depending upon your circuit, but there are two that I’ve been reading up on recently: reducing the clock speed of the ATmega, and sending it to sleep. These techniques might even be essential if you’re planning a solar-powered project.

On an Ardunio board, chip timing comes from a 16MHz oscillator; it probably looks like a little rounded rectangular can just north of the ATmega. This makes sure you get good execution and serial programming speeds, but if your project is simple or doesn’t require that speed, it makes sense to reduce the rate at which the chip is running. Fewer cycles per second should mean fewer milliamps required in use.

In my earlier article I wrote about running an ATmega168 at 8MHz using its internal oscillator to reduce parts. But what about dropping down to 1MHz?

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Security, Energy and Home Automation

http://www.flickr.com/photos/bjdawes/3475478301/

Everybody loves a bit of home automation, don’t they? Traditionally, geeks such as myself would be toying around with X10 modules, which provide a mature platform for automating pretty much anything in your home. But if X10 isn’t your thing, there may be an alternative.

Here’s my admission. I never figured X10 out. If I’d bought a few modules and started playing I’d probably have got a lot further, but I always held back because of the price of the modules and the fact that I already use powerline communication for ethernet, and didn’t really like the idea of putting more interference into my mains supply.

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Mac OS X Energy Scripting

http://www.flickr.com/photos/dan_h/416023415/

We’ve got a variety of Macs running OS X versions 10.4, 10.5 and 10.6. They’re all managed from an Xserve with MCX preferences through Workgroup Manager, but for some reason I’ve just never managed to get them all to settle nicely with their power management settings.

While it’s lovely to have the control of these things through Workgroup Manager, I finally got miffed with it not working, particularly with the Tiger clients. It’s also not good to have rooms of machines burning away power and their components pointlessly.

Terminal

  1 #!/usr/bin/perl -w
  2 
  3 #powerman.pl v1.01 (23/03/10)
  4 # Installed in /usr/local/bin
  5 
  6 # Makes sure basic power management settings are maintained, and
  7 # power down machines when we can get away with it.
  8 
  9 use strict;
 10 
 11 my $clires;
 12 my $logfile = '/var/log/powerman.log';
 13 my $lockfile = '/tmp/powermanpmsetdone';
 14 
 15 # Log housekeeping (erase log if >100KB).
 16 $clires = `touch $logfile`;
 17 my $logsize = -s $logfile;
 18 if ($logsize > 102400) {
 19 	$clires = `echo > $logfile`;
 20 }
 21 
 22 # Let us alter the power management settings if we force it.
 23 if ("@ARGV" =~ 'force') {
 24 	$clires = `rm $lockfile 2>/dev/null`;
 25 }
 26 
 27 # Figure out where we are.
 28 my $hostname = `hostname`;
 29 
 30 # Discover system version.
 31 my $osxver = `sw_vers`;
 32 if ($osxver =~ "10.6") {
 33 	$osxver = "6"
 34 } elsif ($osxver =~ "10.5") {
 35 	$osxver = "5"
 36 } elsif ($osxver =~ "10.4") {
 37 	$osxver = "4"
 38 }
 39 
 40 
 41 # Set some basics, unless we've already done so recently.
 42 if (! -e $lockfile) {
 43 
 44 	my $pmbasics = `pmset -a hibernatemode 0 halfdim 1 womp 1 sleep 0 powerbutton 0 disksleep 30 autorestart 1 displaysleep 9 repeat wakeorpoweron MTWRF 08:45:00`;
 45 	$clires = `echo "\`date  +'%Y-%m-%d %H:%M:%S'\`: UPDATE: General power management settings have been updated." >> $logfile`;
 46 
 47 	if ($osxver >= 5) {
 48 		my $pmleo = `pmset -a ttyskeepawake 1`;
 49 		$clires = `echo "\`date  +'%Y-%m-%d %H:%M:%S'\`: UPDATE: Power management settings for Mac OS X 10.5 and later have been updated." >> $logfile`;
 50 	}
 51 	
 52 	if ($hostname !~ 'cluster') {
 53 		my $pmleo = `pmset -a displaysleep 20`;
 54 		$clires = `echo "\`date  +'%Y-%m-%d %H:%M:%S'\`: UPDATE: Power management settings for studio (non-cluster) machines have been updated." >> $logfile`;
 55 	}
 56 
 57 }
 58 
 59 
 60 # Now we get active with some potential shutdowns.
 61 my $currenthour = `/bin/date +%H`; chomp $currenthour;
 62 my $idletime;
 63 my $consoleuser;
 64 my $ttysuser;
 65 my $sysload;
 66 
 67 # How long have we been idle?
 68 my @idle = `/usr/sbin/ioreg -c IOHIDSystem`;
 69 foreach (@idle) {
 70 	if (/Idle/) {
 71 		my @idlevalue = split /= /, $_;		
 72 		$idletime = int((pop @idlevalue)/1000000000);
 73 		last;
 74 	}
 75 }
 76 
 77 # Is anybody using the console?
 78 my @console = `/usr/bin/who`;
 79 foreach (@console) {
 80 	if (/console/) {
 81 		$consoleuser = 1;
 82 	}
 83 	if (/ttys/) {
 84 		$ttysuser = 1;
 85 	}
 86 }
 87 
 88 # Are we madly processing away on something?
 89 my @uptime = `uptime`;
 90 foreach (@uptime) {
 91 	my @load = split / /, $_;
 92 	$sysload = int((pop @load));
 93 	last;
 94 }
 95 
 96 # Things to do if we're outside our usual hours (0800-2100).
 97 if (($currenthour < 8) || ($currenthour > 20)) {
 98 	
 99 	$clires = `echo "\`date  +'%Y-%m-%d %H:%M:%S'\`: snore: powerman.pl starting an out-of-hours check..." >> $logfile`;
100 	
101 	# If there's no console user, nobody on a terminal session, the system has been idle 20 mins and there's not much activity, shut down.
102 	if (($idletime > 1200) && ($consoleuser < 1) && ($ttysuser < 1) && ($sysload <= 2)) {
103 		
104 		if ($hostname =~ "cluster") {
105 			$clires = `echo "\`date  +'%Y-%m-%d %H:%M:%S'\`: SHUTDOWN: Shutting down the system due to lack of activity out-of-hours." >> $logfile`;
106 			my $shutdown = `/sbin/shutdown -h now`;
107 		} else {
108 			$clires = `echo "\`date  +'%Y-%m-%d %H:%M:%S'\`: If this had been a cluster machine, it would have been shut down due to lack of out-of-hours activity." >> $logfile`;
109 		}
110 			
111 	}
112 	
113 	# If there IS a console user, but they've been inactive for an hour and there's barely a hint of processor usage, shut down.
114 	if (($idletime > 3600) && ($consoleuser == 1) && ($ttysuser < 1) && ($sysload <= 1)) {
115 		
116 		if ($hostname =~ "cluster") {
117 			$clires = `echo "\`date  +'%Y-%m-%d %H:%M:%S'\`: SHUTDOWN: Forcing an out-of-hours shutdown with an inactive console user present." >> $logfile`;
118 			my $shutdown = `/sbin/shutdown -h now`;
119 		} else {
120 			$clires = `echo "\`date  +'%Y-%m-%d %H:%M:%S'\`: If this had been a cluster machine, we would have forced an out-of-hours shutdown with an inactive console user present." >> $logfile`;
121 		}
122 			
123 	}
124 	
125 } else {
126 	
127 	$clires = `echo "\`date  +'%Y-%m-%d %H:%M:%S'\`: heartbeat: powerman.pl just completed an in-hours check." >> $logfile`;
128 
129 }
130 
131 if (! -e $lockfile) {
132 
133 	$clires = `echo "\`date  +'%Y-%m-%d %H:%M:%S'\`: heartbeat: powerman.pl successfully completed it's first run for this boot." >> $logfile`;
134 	$clires = `touch $lockfile`;
135 
136 }

powerman.pl [4.10KB] (260)

So I did what I usually do. Write a script. There’s an excellent blog called Managing OS X which had already covered this issue, so using GregN’s script as inspiration I came up with this in perl.

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