Caffeine Zone™ 2 Manual (v2.0.1)

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by Kuo-Chuan (Martin) Yeh and Frank E. Ritter

Getting Started

The Caffeine Zone is an app for predicting caffeine by showing the time course of caffeine on a strip chart. The chart is based on research results on the pharmocokinatics and pharmacodynamics of caffeine (e.g., Julien, 2001). The details of caffeine consumption is important and often overlooked. Many people feel or are overdosed but have no easy way of knowing and modeling the time course of caffeine and how much caffeine is in their body before we created this app.

Typically, you open up CaffeineZone, and enter the caffeine you are consuming, including the size and amount of time you consume it (which influences the shape of the curve). As you consume caffeine over time, you add further events. The strip chart shows you the time course of caffeine in your body, and has thresholds that you might wish to be aware of. If you find that you can sleep with more caffeine (or less), or you feel alert with more (or less) caffeine, then you can adjust these thresholds.

Home Tab

This is the main page of this app. You can see a chart that occupies most of this scrren. This chart represents caffeine levels and how they change over time. The X axis shows 48 hours of data, divided by a green line that represents the mid point of the 48 hour period, normally the current time. The Y axis shows the caffeine dose (mg) or dosage unit (mg/kg) respectively. Inside the plotting area, you will see a blue zone representing the dose/dosage below which (based on your setting) you should not be affected by caffeine keeping you awake. You will often see a green zone as well which represents the dose/dosage of caffeine in keeping you cognitively agile. Any amount of caffeine above the green zoon is consider too much. These numbers (sleep time and level, Min Optimal level, Max Optimal level, Weight, and display Units) are configureable in the Settings tab.

There are two buttons on the chart area, along the Y axis. On top is the refresh button refresh button. This will update the display. The computation of the curve is relatively expensive and does not change much, so we do it initially and then when the user asks for it. In the bottom is the clock switch clock icon. Tapping this will switch between the two different time modes, displayed in the X axis. By default, Caffeine Zone™ 2 displays time according to the current time. Negative numbers means prior times and positive numbers are future predictions. Another time display mode is the canoncial time that shows the actual time in hours:minutes.

The Consume Caffeine button is below the chart area. It allows users to select from different type of caffeine, dose, consumption speed, and consumption time. There are 3 preset types of caffeine products: coffee, tea, and gum. Gum has a fixed consumption time of 20 minutes. One can also use Custom to customize the input. [this function is not working, 18feb2012, and we are working to fix it.]

History Tab

In the history view, you will see the history of your caffeine consumption. Tapping the trash can icon trash icon will remove all consumption data.

Tapping on a cell of the history view will enable reconsuming that same type and amount of caffeine at the current time. It is useful if you drink the same amount of coffee or tea in the morning.

Settings Tab

Currently, their are several settings you can configure in CaffeineZone: Sleep time and level, Min Optimal, Max Optimal, Weight, and display Units.


Julien, R. M. (2001). Caffeine and nicotine. In A primer of drug action (pp. 220-228). New York, NY: Worth Publishers.

Last Updated: 15 Jul 2014
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