Inexpensive UV Dose Indicator for Water Purification
Publication Date: 2010-Oct-26
The IP.com Prior Art Database
Disclosed is a method for detecting the proper UV dosage for the purification of contaminated water.
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For many years, the Solar Water Disinfection (SODIS) Foundation has been providing developing nations with a simple system for the decontamination of water utilizing UV exposure. This method involves exposing water-filled polyethylene terephthalate (PET) bottles to sunlight in order to harness the disinfecting properties of UV light. One drawback to this approach is that varying amounts of sunlight are required to purify the water depending on weather conditions, and it is impossible for a user of this system to visually determine when the water is safe for consumption.
The concept we envisage that solves the issues described above uses either a silicon or organic (preferably) thin film photocell attached to an adhesive transfer tape. The photocell would charge a thin film capacitor such that when the required radiation dose is achieved, the capacitor discharges and either powers an LED or a reversible electrochromic material. This provides a relatively inexpensive, reusable solution to the aforementioned problem.
An example of a thin film solar cell  is illustrated below in Figure 1.
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The system can be used to charge a capacitor by incorporating resistors in series. An animation of a suitable circuit can be found . In this case, the battery is replaced with the photocell. Once the appropriate dose has been reached (which is empirically determined), the capacitor discharges and lights a button LED (shown below in Figure 2) or a signal with similar power req...