ESP8266 Community Forum

I have an Electrolux air washer which i decided to convert to a smart one. So i have already added necessary relays and can control fan speed and power... One thing left. It has a water control built in. I want to keep the original functionality of the board so i need to connect to the water sensor in parallel.

This water control consists of two metal pieces submerged in water. And 2 wires going to the control board (from now on let's call them water wires)

I have taken the pic of the board and highlighted the part where this water wires connect. This circuit is driven by a 9V ac-ac transformer. Multimeter shows around 1,5-3V of AC current on the metal plates.



So going the easy way i've just connected to the metal plates +3,3V from wemos and then to the analog pin A0 (pulled to ground via 10k). Actually it almost worked. Had reading of around 158 when water present and 60 when not.

But i lost the functionality of the original control board. With +3,3V from wemos connected it always "detected" water even when there was none. (i have tried switching sides with no luck).

So i removed the 3,3V from wemos and just left the analogue pin connected to one of the metal plates. This gives me fluctuation reading from 2 to 30.

So i wonder what is the correct way to go?

Few questions to clarify.

First, are the metal plates insulated from the water by a coating of some description? If so then what you have is a capacitive water level sensor. In this case then search for arduino capacitive level sensors and you will find lots of material that shows how to measure these using charge discharge cycles.

Second, are you trying to get a real measurement of the level or just an on/off indication of water present?

Third, it sounds like you want to get the level or indication while the original control board is still sensing it. Is that right? If so then you need to find out a bit more on how the plates are connected up. E.g. is one of the plates grounded. This will help determine a feasible strategy to use.

btidey, thank you for the follow up.
1. No. They don't seem to be isolated by any coating or lacquer. Just stainless steel plates running across one of the walls and separated in the center. The chip reads HEF4093BT But openning the datasheet didn't help much as i didn't undersand a word there.

2. No. Just an on/off will do perfectly

3. Yes. Want to keep the original board as well. Not sure what you mean under the ground. The air washer is running of a 2 pin (L,N) plug with PE excluded. The original board is a single sided PCB design. Most of it is occupied by a rotary switch controlling fan speeds (2of them) plus a motor for air washer wheels. Than there is a 9V transformer AC transofrmer feeding the water sensing part

*deleted* <written before detailed post came up>