I'm thinking that the other board with the two relays that works may have some delay functions to prevent the sensors from false triggers. Would add more circuitry to the existing design though

 

I did not notice any delay but perhaps we are talking very short interval that would be hard to notice.
The only additional active component on that board is the transistor controlling the relay.
I even removed the large capacitor and placed the small power supply in its place.
Additional components wouldn't be big problem.

Will try the 1K resistor first.

 

Is there a 10uf cap on pin4 of the 555?

 

No, everything is per your original design. The one without diode on the upper level sensor.

 

Should be OK. Try through a 1K resistor first.

OOOOPS resistor did lit like a match and then it blew up
That was entertaining

 

Is everything else OK?

 

Yes, everything works like nothing happened

EDIT
Actually no, the little PS green LED is NO but solenoid will not trigger now, will investigate

 

Good won't try that again.
Try adding a 100uf cap on pin4 to ground on the 555.

 

Hehe, no kidding
Sensors OK, PS OK, solenoid OK, board dead.

Will try the cap with the other board and report back.

 

Good won't try that again.
Try adding a 100uf cap on pin4 to ground on the 555.

With the cap it doesn't work. Removed it, working again

 

Doesn't seem right. Are you sure it was installed correctly. It is polarized.

 

I'll say yes, but I was wrong many times before
Now the negative from pin 1 is disconnected.
The relay wouldn't switch on when power was applied, even with sensors disconnected.
Cap desoldered and all working again.

 

Cap probably too large, try 10uf. The idea is to provide a slight delay, appx 1 sec. when activated by the lower sensor.

 

Will experiment later and report back
Thanks!

 

Cap probably too large, try 10uf. The idea is to provide a slight delay, appx 1 sec. when activated by the lower sensor.

Unexpected results (bench test with the jar for now)
100uF Not working
10uF Plugged it in, PS LED ON and from that time it took about 5s to turn on. After that it stopped working again.
1uF Now when I plug it in and even if the upper sensor is covered it will not turn on, it will wait till the water level goes below the lower sensor, then it refills all the way up, turns OFF, and then working properly. Don't see any delay though.
I actually like it how it works now but will see tomorrow how it will do in the machine

I think we can say "It's predictably unpredictable" ...like German cars

 

1uF Now when I plug it in and even if the upper sensor is covered it will not turn on, it will wait till the water level goes below the lower sensor, then it refills all the way up, turns OFF, and then working properly. Don't see any delay though.

That's normal. Should not begin refill until water is below lower sensor. I would expect the 1uf cap to cause about a 1/2 second delay on the lower sensor which might not be observable.
Agree, what counts is will it work in the machine.

 

Another mod with R3 and C2 if the above doesn't work.

 

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.
View attachment 287732
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.
View attachment 287733

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.

Why do you anticipate that being energized most of the time will be bad for the life of the relay?? Does it get hot while energized? To reverse the operation of the circuit shown, have the collector of the transistor pull down the base of a second NPN transistor that has a pull-up resistor, and the collector driving the relay. A simple inverter is all that is required.

 

Thanks for reply!
No it doesn't get hot but the appliance is on 24/7/365 so that can't be good for life expectancy of relay to be on 99.9% of it's life.
Relays are not designed for that.
The second transistor would probably work but if it could drive the circuit direct that's way more simple, less parts, less power ...

 

Got all excited this morning since there wasn't one single false trigger, sadly at the bottom of the actual tank it did not trigger either. Looks like the capacitor makes the sensor circuit very sensitive. if I remove the polycarbonate tank it will trigger immediately, the glass test jar also doesn't have this problem. Top sensor still working like a swiss watch in both setups!
Will add the resistor and see.