Have you ever woken up feeling completely wrecked when the alarm clock goes off, despite the fact that you have slept “enough” hours? When this happens you have probably been awakened during a deep sleep phase, and your whole day can turn into one long zombie marathon.

Other days you spring out of bed with a smile on your face, feeling completely rested even though you shouldn’t. As the alarm clock goes off, chance seems to play a big role in how your day will become. But does it really have to be that way? This is where the Sleep Cycle alarm clock application comes into play.

During the night you go from light sleep to deep sleep, occasionally entering into a dream state which is called REM-sleep. These are things that your normal alarm clock does not care about, and will go off at the set time regardless of whether you are in a light sleep phase or in the deepest sleep. However, since you move differently in bed during the different phases, the Sleep Cycle alarm clock is able to use the accelerometer in your iPhone to monitor your movement and determine which sleep phase you are in. Sleep Cycle then uses a 30 minute alarm window that ends at your set alarm time and wakes you in your lightest sleep phase.

More info is available in the FAQ

Here are some real life examples of sleep graphs generated by Sleep Cycle.

Example 1: a typical sleep graph

The first example is a text book sleep graph. When sleeping you go through sleep cycles that last for about 90 minutes, these cycles go from deep sleep to shallow sleep and dreaming.

If you look at the graph above you can see that the peaks are about 90 minutes apart – these are the sleep cycles of this person. You can also clearly see that for every cycle the person goes into less deep sleep, this is typical for a normal sleep graph.

Example 2: more irregular sleep with a period of being awake or nearly awake at 7.30am

The second example has a bit more irregular sleep. The user did probably not sleep as well as in example 1. In this example the user’s partner got up at 6am. This is clearly seen – the user was awake or nearly awake at around 6am when her or his partner got up.

Example 3: no or little movement was sensed

This is how a graph will look like when the phone has trouble sensing your movements. If you see graphs like this make sure the placement test in sleep cycle works well. During the placement test the phone should make a sound every time you move in bed. You can also try placing the phone closer to your body.

Example 4: sleep under the influence of alcohol

This example is not a good nights sleep. Although alcohol can make you fall asleep easier it makes it hard to sustain a full night of good sleep. The first half of the night the person goes into some deep sleep but during the second half a lot of time is spent being awake or nearly awake.

More info is available in the FAQ