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Shower Water Automatic Temperature Controller - "SWAT"

Automatic Temperature Controller for Existing Showers

Summary Description:

The Problem

There are millions of homes which have showers that do not contain any water temperature controlling equipment. When variations in water supply temperature or pressure occur, uncontrolled showers can subject their users to changes in the temperature of the shower water. These variations can be caused by the use of hot or cold water by devices other than the shower – for example, toilets, clothes washers and other showers – and hence are very common. These changes are often uncomfortable and sometimes dangerous due to the possibility of scalding by hot water. The danger for children is even greater because of their more sensitive skin. It would be highly beneficial to be able to upgrade existing showers with an add-on automatic temperature controllers so as to protect the users from excessive temperature variations. Existing temperature control solutions, however, consist of replacements to the permanently installed shower hardware. In order to make use of these existing devices, one must disassemble the existing plumbing installation and replace major subassemblies such as the hot/cold water mixing valve with new equipment. Such work usually requires the services of a professional plumber and the removal of a portion of a shower wall; it is therefore prohibitively expensive to add temperature control to most existing non-controlled shower installations.

The New Concept

A shower temperature control device which can easily be retrofitted onto an existing shower is proposed. The act of retrofitting does not require the disassembly of piping nor the use of specialized plumbing tools. The temperature control device measures one or more water temperatures and uses this information to provide the shower user with water whose temperature is much more nearly constant than that which can be expected from a non-controlled shower.

Representative Design

The following design displays a possible implementation of the shower temperature controller. Variations on this proposed implementation are possible which still fall within the scope of the design concept.

A water temperature sensor is mounted to the outside of the mixer valve outlet pipe. A microprocessor measures the temperature of the sensor and uses it to estimate the temperature of the water in the mixer outlet. A control law is used to determine a desired angle setting for the shower control knob. An electric motor controlled by the microprocessor drives the control knob through a gear mechanism to the desired angle. The control knob is mounted on a shaft such that it is turned by the motor and gears, but a splined fitting is provided such that the user turns the shower water on and off manually in the same way as he would if the temperature controller were not present. Furthermore, the electric motor and gears are selected so as to permit manual control of water temperature if the controller fails or is turned off. Power for the electrical system is provided by an electric battery. The temperature is displayed to the user on a digital display. The user can control the computer’s operating mode (such as turning the computer or closed-loop control on and off) by pressing buttons on the face of the case in which the electronics are mounted. Also, there are preset buttons on the controller that can be programmed for individual users, similar to seat position in luxury cars, such that by pressing the users number key, the preset temperature level is reached and maintained during the shower. The display, buttons, battery, motor, circuit board, and gears are enclosed in a watertight container as depicted in Fig. 1.