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Here are some of the frequently asked questions about the Lucid Dreaming App:


Updated 05/23/11

  • Q:My graph splits in two segments over  the night

A: Most likely the the phone turned off or memory issues caused the app to shut down. When app restarts, part of the data is missing, which may make the graph appear weird and segmented. Try closing other apps or enabing airplane mode for the night to prevent memory issues.

  • What’s a light strobe, how do I use it?

A light strobe is an attempt at making the phone screen light up to its maximum brightness for a short time and switch between bright and dark background, causing notable light flashing effect. This is very visible if you are sleeping in a certain position with a phone in front of you. For example I sleep on my right side, facing the phone. When it lights up, I see bright light through my closed eyelids. The key is to time this properly to be seen in a dream.

  • App only shows X minutes of sleep, I know it should be more

This is a known issue with the app not working properly with the accelerometer (Check this post for known issues). You have 2 options: perform extended calibration of the app for 30-60 minutes or restart the phone before using the app and seeing if that helped.

  • How do I determine when my REM episodes are?

After using the app for multiple nights, you will accumulate a few dream markers, and activity graphs. When you plot them using splash screen> menu>view data>history , you will see that some of the activity levels appear at the same time.  Check out this post on how to work with history and configure smart timer

  • Does the app support X sound format?

The app uses your phone’s built in media player, and can play all formats supported by the player. If you use OI File manager to pick audio files, you would be able to browse your file system and pick any audio file. Pressing “test reminder” plays the current reminder. If you hear it, it is supported!

  • What is app calibration?

In terms of calibration, there are 2 things that have to be determined.

  1. All accelerometers have different resolution and different noise characteristics.
  2. They are also digital, so the range of measurements is broken into 256 or so segments.
  3. When a phone is at rest, the accelerometer randomly jumps from one digital value to another (lets say from 79 to 80 to 81.
  4. Calibration determines how big each jump is. For example from 79 to 80 is 1 step or 0.04 m/s^2 on my phone, but it may be 0.06 on another phone.
  5. The app then uses this information to create a +/- 3 digital steps envelope around the true signal and uses that information as variance for a simple Kalman filter which approximates the true position of the signal.

  • Is there an iPhone version?

iPhone version is being considered and may be released during 2011

  • How do I use feature X?

The app constantly gets new features, and the best way to find out how to use it is to check the news on the main page. Usually I post a feature preview before introducing a feature. Those posts should have some info on the feature.

  • What is audio level Kurtosis?

Kurtosis is a measure of how “pointy” the signal distribution is. Kurtosis of 0 means the signal is very even, such as a ceiling fan hum. A high kurtosis indicates rare loud sounds being present, such as saying a word into the mic, irregular snoring, cars honking outside, etc.

  • How do I use the WILD gesture?

Go to preferences> edit gestures to see the current WILD gesture. Add your own gesture called “wild” if you want. Drawing this gesture immediately schedules a set of timers that you have set up in the “Configure WILD timers” in preferences. Drawing the gesture again cancels currently running WILD timers. The WILD gesture is intended to be used at the beginning of a WILD attempt.

  • How do I use the Math gesture, what is it?

Draw the M letter (to see exact shape, so to preferences> edit gestures). It brings up a running clock dialog asking you to add two or 3 digital clock numbers. Use this to awaken your brain a bit for WBTB technique or other techniques requiring a certain level of awareness.

  • What is Pr under the clock?

This is the flaw in the current 7 segment LED font used to draw digital clock, it should actually say AM or PM, but does not have enough segments to do so. I have 3 other fonts(14 segment LED), which do draw the letters, however, they are not monospace, so the letters constantly shift as their shape changes, which is also annoying.

  • My partner moves a lot at night, how do I mitigate this?

This is a major obstacle to accurate actigraphy, and there’s no solution currently in place. Check out the latest sound level monitoring, maybe that would help you determine where your own REM events are. Additionally, there’s a silent strobe reminder available which should not be seen

  • Did I lose data from the last night?

By default, the Android Lucid Dreaming App app saves data to your SDCard every 10 minutes, and also saves data when the app is killed by the Android system. Exit button on the clock screen also stops data collection and saves data. To see your data from the last night, open the app again, press “menu” on the splash screen (2 Androids) and select “View data”. Then select “Load Graph” and find a graph with the day/time when you started the app for the night which you want. For example last night, May 22 2011, I started the app at 11:30PM (23:30). The graph for that day would be called Data_20110522_2330.txt.gzip . Opening that graph loads it and displays it in the graph viewer.

  • How do I properly close the app?

When the app is running, 2 triangle (subject to change) icons are shown in the taskbar. When they are there, the app collects data. To exit the app, start it, and from the screen with the clock, select “Exit” from the menu. This will make the triangles disappear and will stop the app.

Additionally, you may individually terminate the data collection services from the taskbar, if the app crashed and you dont want this data collection to take place.

  • None of my reminders played… why?

There are several things you may check

  1. Ensure you have a reminder present and selected by the app. The default folder is SDCard/Recordings
  2. In the Smart Timer, click on an event and ensure that checkboxes next to sound, vibration or light are checked and that the event is activated. Press test reminder to see how it would work
  3. Your Smart Timer events may be set to be active “after movement”. If not enough movement was detected, these will not play. You may check the sensitivity in Menu>Preferences>REM Prediction>REM prediction activity threshold. Lower this setting based on how high your sleep score jumps on movement.
  • Does the app automatically detect lucid dreams and dreams?

It is physically impossible to detect dreams and lucid dreams using actigraphy. Such information has to be manually added by the user upon awakening using the  on-screen gestures.

  • What are the blue blocks on the graph?

These are sleep episodes – periods of total motionlessness. This is where the body is most likely to be in deep sleep with the muscles paralyzed. These are frequently encountered early in the night, but get shorter as the night progresses.

  • What about that send data anonymously feature, I’ve seen it somewhere?

It’s exciting that you are asking about this. While this feature is not currently available, it should benefit the advancement of sleep science, particularly actigraphy based sleep apps. No experiments of this scale (tens of thousands of people over a long period of time) have been conducted, and I’m hoping data like that would help scientists find out something new!

  • How do I transfer the data to the PC?

You can use the built-in screenshot feature to take a screenshot o the night’s data – this image would be found in the /sdcard/application data/lucid dreaming app/screenshots. The file would have a .png resolution and a filename being the same as the graph that you took an image of.

The data itself is in JSON format, stored in a text file which has been compressed using GZIP algorithm. Additionally, a running log is maintained in the SDCard/application data/lucid dreaming app/log , which may be processed with spreadsheet applications.


Help! I experience inconsistent data and the app scores no sleep at all.

Check this post for well known issues. You may need to power off your phone, let it cool down and turn it back on before using the app.  Try to kill some background apps and turn on the airplane mode, this may prevent some apps from updating through the night.

How long do I have to calibrate the device for?

-The app determines the accelerometer’s paramters in just 4 minutes, discarding the first minute. For best results, calibrate it for 7 minutes. If it is still very noisy, you may need to turn off your phone, let it cool down before turning it back on. This seems to cancel out noisy measurements. I had decent results with as little as 7 minutes of calibration, but I got to know my accelerometer really well. To diagnose your issues, there’s a “calibration log” available in the /application data/lucid dreaming app/calibrationLog.txt which shows the xyz readings obtained from the sensor during calibration. These should be very close to 0. If they are not, try to reboot the phone and recalibrate.

My device is too sensitive/not sensitive enough. What can I do?

-You still have to calibrate, at least for 7minutes, then go to Preferences> Sensitivity tuning and set the new activity level which will be considered sleep. Please note that this will affect how the app scores sleep. The default sleep scoring constant of 0.0033 is used to distinguish between sleep and wakefulness.

I did not hear the voice reminder last night, what’s wrong?

-Your early, mid or late night app behaviors may be too long. The defaults are intentionally set to longer than most people may experience. Adjust them after a couple nights, once you see your sleep graphs and can figure out how long your sleep episodes are. You may also want to check the volume level of the reminder or if the reminder is present at all by selecting “Play current reminder” from the preferences.

I experienced a force close doing something. How can I get it fixed?

Please submit a bug report and it will be fixed!

The app spews unreliable data, what’s wrong?

-Check that you calibrated the app for long enough. You can adjust the sensitivity level. I expect that some phones may have issues with the app. Please help me compile a list of phones with issues.


How do I…

Edit a graph?

The graph is stored in a plain text file which has been zipped to save space. The format is GZIP. There must be tools on the market to unzip such files. You can then edit the data. The app recognizes both .txt and .txt.gzip formats. The file name still has to start with Data…

Share a graph?

Your graph contains all the information required to view and interact with the graph. Just find it in the /application data/lucid dreaming app/graph data folder(filename is displayed above the graph) and send it to another person with the app. That person can put the graph in the folder above and view/interact with it!

Compare graphs?

Use the history feature available from Menu>View Data > View History. For best results, put up to 7 graphs you want to compare in a single folder, when select it using the “create history” menu option. This takes about 7 seconds on HTC HD2 with 1ghz processor. On slower phones it may take a lot longer. To avoid waiting this long, you may “save” your history by selecting “Save History” from the menu. Loading history is a lot quicker than re-creating it every time! Plus it allows you to mix and match your graphs and create different history combinations.