Sense water presence and engage relay ...

Thread Starter

now_emailme

Joined Jul 2, 2021
1
Hello friends, I need help. Can you please help me with a circuit (without ardiuno etc) that helps for:

1. Senses water presence.
2. If water presence detected engage the relay to operate external load (220v/10A).
3. If water presence not detected disengage the relay to stop the external load (220v/10A).

I know this can be achieved by Float Switch but that's not my choice as in my case I can't place the float switch at the source, which is a narrow (1/2 inch) and deeper (4 meter) tube (only sensor can go inside).

Thanks in advance.

Regards to all community members.
 

camerart

Joined Feb 25, 2013
2,761
Hello friends, I need help. Can you please help me with a circuit (without ardiuno etc) that helps for:

1. Senses water presence.
2. If water presence detected engage the relay to operate external load (220v/10A).
3. If water presence not detected disengage the relay to stop the external load (220v/10A).

I know this can be achieved by Float Switch but that's not my choice as in my case I can't place the float switch at the source, which is a narrow (1/2 inch) and deeper (4 meter) tube (only sensor can go inside).

Thanks in advance.

Regards to all community members.
Hi N,
My first thought it 'Is it hard water or soft water', remember that hard water will block open sensors.
Can you describe better, what's happening? Is it a flow, or a drip, I presume by the sound of the relay, there is quite a volume, but it's hard to solve it without clearer information.
Cheers, Camerart.
 

Yaakov

Joined Jan 27, 2019
3,736
To amplify what @camerart said, a description of the actual function of this arrangement, a drawing (even if very simple) showing the geometry and parts involved, and any specifications you have on things like motors (I am guessing there is a pump involved) would go a very long way to getting real help.
 

LesJones

Joined Jan 8, 2017
3,570
I second Ian's suggestion of a washing machine pressure switch. Some of them have sets of contacts which change at slightly different pressures. (Hence slightly different water levels.) This could be used to avoid rapid on/off cycling of the pump. I would avoid the electrical sensing method as it could give problems with corrosion of the electrodes. Also residual moisture causing the pump to run even when the electrodes were not immersed in water.

Les.
 

dendad

Joined Feb 20, 2016
3,939
The washing machine switch idea may a good way to go. They are simple and readily available.
You could install a couple with different length tubes, and if they are multi contact switches, then you could end up with 4 levels.
One problem could be, over time, the air in the tube may get dissolved in the water, or leak out so the sensing will change greatly, or even fail.

But I would not dismiss an Arduino just out of hand.
The water detectors (for flood irrigation) I made use an Arduino and a couple of probes.
One probe is capacitivly coupled to a PWM output, and the other probe is also capacitivly coupled but this time to a rectifier that feeds an analog input.
The Arduino reads the analog input with no PWM running to get a noise level and than turns the PWM on at 50%, after a short delay, the analog input is read again and if these is a significant jump in the level read, then water is there.
A number of sensing probes of different lengths may be used for rough level sensing.
Adding an Arduino allows you to do such things as displays, timed operations and other things like reading the motor temperature, current and flow etc to help prevent running the pump dry for example.
And you could add communications for remote indications of the state on the system

Another sensor may be a pressure sensor at the bottom end of the intake pipe to measure the head on water above.
 

Reloadron

Joined Jan 15, 2015
6,204
If the sensor:
which is a narrow (1/2 inch) and deeper (4 meter) tube (only sensor can go inside).
is a sight glass you can consider an optical arrangement. Beyond that, as mentioned, a simple pressure switch as used in washing machines. Many are adjustable giving you some working room.

Ron
 

kaindub

Joined Oct 28, 2019
92
The water level switches I have seen in washing machines are plastic tubes connected to a MEMS pressure sensor. The attached microprocessor does the calculation.
The problem with the tube in water is that due to ever so slight air leaks the tube starts to fill with water. This makes measurement of the level inaccurate.
This system works in washing machines because for every wash cycle the bowl is drained fully, so water does not stay in the tube.
 

dendad

Joined Feb 20, 2016
3,939
The water level switches I have seen in washing machines are plastic tubes connected to a MEMS pressure sensor.
The older ones have micro switches in them, but I agree with your comment on them sometimes leaking and needing to be fully emptied often.
They are not really suited for long term accurate use.
 

Phil-S

Joined Dec 4, 2015
224
In the dim and distant past you could have used an LM1830
https://www.hobby-hour.com/electronics/fluid_level_control_schematics.php
Washing machines achieve it with a tube which is placed in the water at one end and sealed at the other end, and equipped with a pressure switch. As the water level rises, the air pressure in the tube rises and operates the pressure switch.
I remember the 1830 well and used it many times in industrial monitoring.
It had everything a water sensor should have, including AC driven electrode source, but for whatever reason, NS decided to pull the plug on it.
I used them for pump control in waste water tanks and for pump rotection.
 

Phil-S

Joined Dec 4, 2015
224
Water leaks can prove very costly, as I know.
I knocked up a simple circuit using just one CMOS 4011 chip, it latches on, optional, and has a bleeper output plus an open collector output.
The impedance of the CMOS inputs is so high that a DC source matters not at all.
If the £8 circuit saves £800's of damage that's fine.
It draws way less than 1-uA in standby.
I've dotted them around under kitchen units, baths, loft tanks.
Easy to connect to any radio for remote situations, relays etc.

PS There was mention of the type of water to sense.
Obviously, this doesn't apply to pressure switches, but for conductivity based measurements, it does.
I've tested the CMOS device from rainwater and boiler condensate, essentially distilled water through to tap water.
Rain water and boiler condensate are about 120-microSiemens per cm and the chalk tap water can be up to 500-uS/cm.
I would agree about the inlet tube of pressure switches gradually letting water in, I've seen it happen on dial gauges.
On vacuum pumps, there used to be an inline filter for condensed water which was essentially a disk of PTFE membrane that allowed air through, but not water.
 
Last edited:
Hello friends, I need help. Can you please help me with a circuit (without ardiuno etc) that helps for:

1. Senses water presence.
2. If water presence detected engage the relay to operate external load (220v/10A).
3. If water presence not detected disengage the relay to stop the external load (220v/10A).

I know this can be achieved by Float Switch but that's not my choice as in my case I can't place the float switch at the source, which is a narrow (1/2 inch) and deeper (4 meter) tube (only sensor can go inside).

Thanks in advance.

Regards to all community members.
You might want to consider this liquid level sensor from Sparkfun Electronics
Hello friends, I need help. Can you please help me with a circuit (without ardiuno etc) that helps for:

1. Senses water presence.
2. If water presence detected engage the relay to operate external load (220v/10A).
3. If water presence not detected disengage the relay to stop the external load (220v/10A).

I know this can be achieved by Float Switch but that's not my choice as in my case I can't place the float switch at the source, which is a narrow (1/2 inch) and deeper (4 meter) tube (only sensor can go inside).

Thanks in advance.

Regards to all community members.
You might want to consider this liquid level sensor from Sparkfun Electronics. I have attached a screenshot. And here’s the description.
The eTape Liquid Level Sensor from Milone Technologies is a great way to measure the level of a liquid. It has a resistive output that varies with the level of the fluid. It does away with clunky mechanical floats, and easily interfaces with electronic control systems. The sensor's envelope is compressed by the hydrostatic pressure of the fluid in which it is immersed. This results in a change in resistance that corresponds to the distance
from the top of the sensor to the surface of the fluid. The sensor's resistive output is inversely proportional to the height of the liquid: the lower the liquid level, the higher the output resistance; the higher the liquid level, the lower the output resistance.

I HTH,
Phil
 

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