Flood sensor using detection rope


#1

I’d like to use water detection cable with the GrovePi to make a flood sensor. A small (<1cm) puddle of water at any point along the length should trigger it. I’m hoping that all the Grove needs to do is watch for a closed circuit across the two wires.
Which port should I connect it to?
Which python project should I use as a starter? I’m comfortable coding to the sensors in the starter kit.

As these are bare wires how much current could be running down them? Would that give a zap or tingle to anyone accidentally touching it whilst live? Could it touching the wrong thing damage the Grove somehow?

For cable I’d be looking at the WDC2 from here:

Specs:
Sensor wires:
Annelid 0.4mm diameter Stainless Steel
Sensor resistance:
7Ω per metre per sensor wire (14Ω per cable metre)

Thanks


#2

Hi @mamoulian,

This Grove Water Sensor can detect water and it can be attached to GrovePi easily. This sensor has twig module which has two set of traces which are used to detect water. One set of traces are grounded while the other set of traces are pulled up by a 1M ohm resistor and connected to the signal pin. When there is no water on the traces a HIGH Voltage(5V) is observed on the signal pin. When there is water on the traces, water acts as short circuit and grounds the Signal pin, pulling it down to LOW Voltage(0V).

These two set of traces can be replaced with the detection wires which you wish to use and you can use the principle described above to build a circuit with your detection cables at your own risk.

Please let us know if this helps,
-Shoban


#3

Thanks, sounds good!

What would you feel if you touched the water sensor’s traces with a finger?

Could static going back up damage the grove or pi?

What length would be practical at 14Ω per metre?

Thanks


#4

Hi @mamoulian,

Nothing will happen if you touch the traces of the water sensor as the voltage that it is operating on is very low and the impedance offered by our body is large compared to it. The length of the wire won’t affect much as there is a one Mega ohm pull so even a 10 meter wire will offer a very less resistance when compared to 1Mega Ohm.

-Shoban