Water overflow and empty indicator and reset alarm

[bilalinamdar]

Hello
I want to build a circuit which will alert me when oht is overflowing and when it is empty*

This is the circuit I build using google
Please refer to the image schematic

R1220k
R2 22k
BC557 pnp transistor (empty)
Bc548 npn transistor (overflow)
Relay 6 or 12v
Power supply 9 or 12v
Probe H (overflow sensing) top
Probe E (empty) below middle above probe c
Probe C common for H and E


I don't know much abt electronic but it is my hobby. I m not able to resolve the problem

Problem
The above circuit works gr8 separately but I want to combine both so that they can work together. I know diodes will be needed but kindly explain me where should I use it*

1) i want to drive the relay when the overflow is sensed
2)I want to drive the relay when empty is detected
3) Also I need a indicator for empty and overflow (led red and green)
4) reset button to shut the see below relay desc

What relay will do?
Relay will drive AC door bell. I want something like a bell button or reset button which when pressed and released will disconnect the sound of bell. But will still be armed for next condition match is it possible? *Just like alarm clock when reset is pressed the bell turn off but will sound again after the next alarm hour is met.

Schematic image
**broken link removed**
Tank display
**broken link removed**

 

[SughiRam P.]

The Diodes u r talking is fly wheel diode. You should connect it across the coils of Relay as the diode should be reverse biased. For Instance say, the relay coil is charged for sometime. Now disconnect GND from relay coil. i.e Transistor BC557 turned OFF. now, the coil oppose sudden change in current. So, an EMF is induced by relay coil which is of opposite polarity of Relay coil connection. This Counter EMF may affect the transistor. So, we are using diode to prevent any damage due to this EMF. Diode is forward biased for this Counter EMF. Finally this energy circulate in diode itself and ceases.

 

[SughiRam P.]

For more on flywheel diode see attachment.

 

[bilalinamdar]

The relay doesnt work even after adding the diode
Thx for the flyback solution I read the PDF. I just now know that we should always use flyback. Gnd -->|-- positive on relay coil is that right ? Also why doesn't the relay work ? In my case.

 

[bilalinamdar]

I dropped the plan of the above circuit because the problem is caused by the pnp is not solvable by me
So I got a good Sch from net tested and working

**broken link removed**

I want ask few things I edited the circuit a little

Pnp transistor is for empty water in the circuit
So pnp configuration

Collector to ground
Emitter to diode. (E |< device negative) (device positive to +12v)

Npn configuration

Emitter to ground
Collector to diode ( C |< device negative ) ( device positive to +12v)


Is the editing okay ? Is there any problem ?

The device are same ( it can be a relay with flyback)

-------------

Other thing i want to ask if suppose I want to add a reset switch which will function as a on off device for the device ( buzzer) and reinitiate again only to turn off the reset switch must be used. It must rearm it self again if the output state changes ( of ic 4050) ( state change on pin 4,15)
Please help

 

[Avinaash]

@bilalinamdar

Hello bilalinamdar ,

Thanks for the link and verifying the circuit. In the circuit diagram, the supply wire is suspended in the tank. Is it fine to leave the supply wire like that? Are there any chances of shocking when we use the water from overhead tank? You said that you made changes to the circuit. I'm unable to understand the description. Could you please provide a rough sketch of the edited diagram?

Thanks!!

I dropped the plan of the above circuit because the problem is caused by the pnp is not solvable by me
So I got a good Sch from net tested and working

**broken link removed**

I want ask few things I edited the circuit a little

Pnp transistor is for empty water in the circuit
So pnp configuration

Collector to ground
Emitter to diode. (E |< device negative) (device positive to +12v)

Npn configuration

Emitter to ground
Collector to diode ( C |< device negative ) ( device positive to +12v)


Is the editing okay ? Is there any problem ?

The device are same ( it can be a relay with flyback)

-------------

Other thing i want to ask if suppose I want to add a reset switch which will function as a on off device for the device ( buzzer) and reinitiate again only to turn off the reset switch must be used. It must rearm it self again if the output state changes ( of ic 4050) ( state change on pin 4,15)
Please help

 

[ALERTLINKS]

In the schematics PNP tansistor is shown connected wrong way.

Here is corrected connections.

The buzzer will continue sounding until level reaches to lower 2nd wire. Similarly start sounding when upper level is reached and remain in this condition until water level is lowered from top sensing wire.

 

[ALERTLINKS]

Here is away to put relay in te circuit with reset switch.

 

[KMoffett]

Using DC excitation, in continuously submerged electrodes, will cause electrolytic corrosion of the electrodes. It works OK flood alarm circuits, but not for continuous level monitoring. I would go with a variation of this:**broken link removed**
Use one gate for the driver and a gate for each level you want to indicate.

Ken