My biggest problem with all of the UV light based water filters on the market is the switch on the UV light. The cable from the switch to the filter is only about 50cm long. If the filter is installed under the sink (where else would you want to install it if you had a choice?), then you have to get down on your knees to turn the switch on under the sink so that the UV light is on when you are running water through the filter.

And according to the vendor’s own installation person, you must turn the light off after you use it since it is designed to be on with running water to cool it down. If it sits in non-running water, it will heat up and the life span of the bulb goes down dramatically. But after you’ve gotten the water you wanted, it is very easy to forget about getting back down on your knees to turn off the switch. And did I mention that my knees are too old for this? And my mother in law doesn’t stand a chance.

So we came up with a simple enough solution at my office that I decided to replicate at BaanMae. (Simple enough for a “maker” that is.)

We connected a 220V relay to an ATmega168 microcontroller which turns on and off the UV light and mounted it in a sealed box under the sink. Here is a picture of the setup under the sink:

The grey box on the left contains the microcontroller, relay, small buzzer, and a 220V to 5V adaptor to drive the microcontroller. The yellow and black AC socket on the bottom of the grey box is the relay controlled outlet the the UV light power supply (on the right with the white hood) is plugged into. If you look carefully, you can see the switch hanging down just a few centimeters from the yellow and black outlet.

The microcontroller is also connected to a remote push button and LED mounted on top of the sink. By pressing this button once, the buzzer beeps once, the UV light turns on, the LED next to the button lights up to let you know the UV light is on. Pressing it again turns of the LED light, the UV light, and causes the buzzer to beep twice. If you forget to turn it off, it is okay, since the ATmega will count out 5 minutes (more than enough to fill up any water bottles you might be filling) and then turn the UV light off automatically.

All very simple and within reach!

Here is a picture of K’Tanawat pressing the button to test it:

And here is a wider view to see where the whole thing is installed under the sink:

The red arrow points to where the outlet is under the sink. (Away from probable water leaks to prevent electrical problems, but that makes it even harder to reach down and turn it on and off easily.) The little push button hack makes getting UV filtered water much easier!