Automatic water filler circuit with touchless water level detection.(initial question "Inverting sensor output voltage")

Thread Starter

Lifeisfun

Joined Feb 17, 2023
92
Hi folks,
I'm having problem modifying some components to work together to operate properly.
I'll start with the 5V NPN contactless water level sensor.
DC-5V-Non-Contact-Liquid-Level-Sensor.jpg
It works great, however it outputs 5V when water is detected, so the mini relay that it's driving is on most of the time and I don't think that this is that great for the relay life expectancy. There is 2 of them, one for high and one for low level detection.
I'm looking for solution to invert the output to 0V when water level is detected, or even better to eliminate these relays and connect the sensor output directly to the controller below.

These relays switch inputs on 5V water level controller based on NE555 IC. This controller has 3 submerged probes ( just wires) and it controls the pump. The common probe terminal (A) is not connected directly to the positive or negative 5V of the controller.
Sac286b97a68d46189d5d2eae043f7c89W.jpg

I can't use the exposed wires to detect the level so I'm looking for reliable solution how to combine these two components together.

Any help would be appreciated.
 
Last edited:

Thread Starter

Lifeisfun

Joined Feb 17, 2023
92
More thoughts I did not managed to squeeze in within the 10min edit period :)
I did try to connect the sensor direct to the B/C terminals - did not work
Here is how the sensor board looks
sensor5V_.jpg
 

Thread Starter

Lifeisfun

Joined Feb 17, 2023
92
If you have a volt meter we can check the levels on the A,B and C terminals. The water sensor you listed appears to pull the black wire to ground so this might work with that relay module.
Thanks for reply!
Yes, will measure and post voltages. Controller powered on, no sensors connected. In this state the pump relay is ON.
Left measured positive to each terminal for probe, right negative to probe terminals.
PXL_20230217_153501300.jpg



It works fine with mini relays (40mA draw each relay directly connected the sensor)
PXL_20230217_152500808.jpg
 
Last edited:

sghioto

Joined Dec 31, 2017
5,369
I think all you need is a different relay module that will accept either a high or low signal trigger like this 5 volt unit.
HiLetgo 2pcs 5V One Channel Relay Module Relay Switch with OPTO Isolation High Low Level Trigger
7.39 at Amazon.
1676648716552.png
 

Thread Starter

Lifeisfun

Joined Feb 17, 2023
92
These relay modules will replace the modules you have now. The sensors connect directly.
Are you sure? I think these will just turn on or off with the option to set the jumper on 0V or 5V trigger.
The controller I'm using now will turn on the main relay when water drops below the Low sensor, and will stay on till the water level reaches the High sensor, then it will turn off the relay and wait till it drops all the way down again.
 

Thread Starter

Lifeisfun

Joined Feb 17, 2023
92
Then what is the problem if it's working as you say?
Show how you have that black relay wired.
It's working fine, my "problem" is that the relays need to be there, or do they?
Problem no2 is that they have power on the coit 99.9% of the time since those sensors give 5V output when the detect water.
Not the greatest for power use ( not the main concern) but reliability.
I can't use the other relay contact since if that circuit would fail (no power) the pump would flood everything.

So ideal solution would be to drive the controller input direct without relay or revert the sensor output to 0V when water is detected.
 

Thread Starter

Lifeisfun

Joined Feb 17, 2023
92
From what I'm seeing the output from the sensor is zero when water is detected from the schematic of the sensor.
No, the relay is on when water level reaches the sensor.
Positive 5V is connected to the relay and the sensor will connect the ground when it detects water.
Tried the opposite way but the relay will not turn on.
 

Thread Starter

Lifeisfun

Joined Feb 17, 2023
92
Correct but the sensor output is actually 0 volts.
View attachment 287765
Well, , yes, that's correct, it will ground the relay and complete the circuit.
I guess I did not explain it in proper terms.
So I need to reverse that and have no power on the relay when there is water detected.
I presume transistor can do that. I tried but failed miserably :)

I'm sure someone can figure out how to eliminate those 2 relays together but I understand without the controller diagram that is not easy.
There is plenty of examples I found but not sure if they match exactly the one I have. Most of those I found are using positive as common for those 2 probes in the tank.
 

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Thread Starter

Lifeisfun

Joined Feb 17, 2023
92
There is a way with the 555 chip. I'm not home presently but it can be rewired as required
That would be great!
I tried to map the board but with all those small smt components it's not easy.
I posted some voltages in the 2nd post but I can measure anything else needed.
Thank you very much for your time!
 

LesJones

Joined Jan 8, 2017
4,174
What is the part number of the 8 pin IC on the relay board that you show in post #. If iy is a comparator then it may be possible to modify the board to give reversed operation.

Les.
 

sghioto

Joined Dec 31, 2017
5,369
20230217_114832.jpgTry this arrangement.
When the tank is full both sensor outputs are low and so is the output from the 555. When the water level drops below the bottom sensor both sensor outputs will be high triggering the 555 output high.
D1 and R1 form a latch function to keep the output on the 555 high as the water level rises and the bottom sensor goes low again.
When the water level rises to the top sensor the low output will reset the 555.
 

Thread Starter

Lifeisfun

Joined Feb 17, 2023
92
What is the part number of the 8 pin IC on the relay board that you show in post #. If iy is a comparator then it may be possible to modify the board to give reversed operation.

Les.
It's NE555
That main board controller is working perfect, no water relay is on, watter detected relay is off.
I need to figure out the probe side of things.
 
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