Creating a wireless water sensor

Someone in the forums mentioned the need to activate a pump on the rare occasions when their basement would flood. Here is a very simple hack to the wireless door button in the Ninja Blocks kit to turn it into a water sensor.

Rather than shorting two contacts with the button, we'll bring each side of the button out and let the water do the shorting.

NOTE: obviously this kind of hack is not appropriate for high-voltages.

At the end of this, the device will constantly transmit while there is water present. This is handy for situations like activating a pump while water is present, but not ideal for say detecting rainfall.


- Small philips head screwdriver
- Soldering iron + solder
- Two wires

Accessing the button

Using the philips head screwdriver, open the battery panel then remove the top panel with the button.


Solder one wire to the top-left pin of the button.
Solder the other wire to the top-right pin of the button.
Tip: Pre-solder the end of the wire and the contact you will connect it to
Verify your contacts by shorting the other ends of the wires (the ends that will go in the water).
This light should blink as it transmits no different to if the button were pressed.

Finishing up

With the wires soldered, guide them as shown in the above diagram.
Seal the top panel and battery panel, ensuring that the wires neatly exit the white housing as shown below.
Test your creation by dipping the free-ends of the wires into water. The light should blink as if the button were pressed, but perhaps not as bright.
Now you can install this above the area that you wish to monitor. For best results, space the free-ends of the wires with a small (1cm) air gap between them.

Installed in the basement, ready to transmit when water is present.

James Zaki
James Zaki