I am a big fan of the LV version of the Pololu mini pushbutton power switch (2808) that has now been available for over a year. This module is, in fact, an electronic power switch capable of turning any device on or off by using either the mini push button on the board or an external on, off, or control signal. It can handle 2.2 to 20 V at up to 6 A. It can be very useful for many projects. Presented below is an admittedly unorthodox design based on the same Pololu 2808 switch to make a portable and expansible showerhead light.
A common showerhead light (with or without a battery) emits gradient light of different colors at the moment of spraying the water. But my intention is to build a small LED light that works like an extra light source above the showerhead in my dingy bathroom. From the picture shown below, we can see that it is very easy to build a showerhead light by modifying a generic clip-on gooseneck LED light. What we need in addtion to the Pololu module is one high-power white LED and a suitable battery pack.
The prototype of the circuit was constructed on a piece of perforated stripboard. It is best to build the circuit into an enclosure (for example, into a defunct clip-on light) that also supports the charger input socket (J1) and the additional push switch (S1).
The socket and the switch can be fitted in any desired location. The onboard pushbutton on the Pololu 2808 or the external pushbutton can be used to turn the white light on and off. It would be easy to attach a “water sensor loop” to the switch interface JP1. Two bare wire loops hang just below the showerhead (see next figure) so that when water touches the wires, it closes the switch connection and the switch turns on, energizing the white light source. I was surprised to note that the control input worked well with small current that flowed through a splash of water from the showerhead. Yes, tap water is conductive enough to actuate the Pololu switch!
Please note that the Pololu 2808 switch has several drawbacks when compared to mechanical switches, so be sure that you fully understand this product before using it in your project (https://www.pololu.com/product/2808).
An old (discontinued) version of a near-same low-voltage Pololu pushbutton power switch (http://www.pololu.com/catalog/product/751) is still available in India for under $10 from here: http://www.rhydolabz.com/robotics-robotic-parts/