Automatic water tank filler.

Hello guys, i'm working on a project to automatically control water flow to the main tank based to water level in the tank itself.
water pump operates when water level reaches the set point and shuts down when it reaches the marked point.


when water is low (lower than ST1) TR1 is triggered through RY2 and the pump runs, when water reaches ST1 , Q2 Conducts thus it energize RY2 which cuts the supply of the TR1 gate. when water reaches ST2 , Q1 conducts and RY1 gets energized which in turn disconnects TR1 anode from supply then water Pump stops. when water drops below ST1 . Q2 turns off and so as RY2 then TR1's triggered through its gate.
when i run this circuit on breadboard everything runs as planned except the last part (When water drops below ST1 water pump should starts again but sadly it doesn't). please if you can point me to my mistake i'd be very grateful. thanx.
 

Alec_t

Joined Sep 17, 2013
10,592
Welcome to AAC!
Are ST1-3 just electrodes dangling in the water? Is so, this is unlikely to work. Pure/clean water is not very conductive, so the transistor base current, and hence the collector current, probably won't be enough to cause the relay to activate. Also, electrolytic action, when using DC, will cause rapid corrosion of the electrodes.
 
Welcome to AAC!
Are ST1-3 just electrodes dangling in the water? Is so, this is unlikely to work. Pure/clean water is not very conductive, so the transistor base current, and hence the collector current, probably won't be enough to cause the relay to activate. Also, electrolytic action, when using DC, will cause rapid corrosion of the electrodes.
they're insulated wires, and the relays activate at the 2 points but the TRI doesn't work after the water drops to low level.
 
when i run the circuit water pump starts and water is flowing to the tank, when water reaches ST1, relay1 gets activated which cuts current off TR1's gate. when water reaches ST2 ,relay2 gets energized and water pump shuts down. when water level drops below ST2 and still above ST1, relay 2 gets deactivated and when it drops below ST1 ,relay1 deactivates which should pass current to TR1's gate through it's Normally Closed contact but TR1 doesn't work at this point.
 

absf

Joined Dec 29, 2010
1,942
when water is low (lower than ST1) TR1 is triggered through RY2 and the pump runs, when water reaches ST1 , Q2 Conducts thus it energize RY2 which cuts the supply of the TR1 gate. when water reaches ST2 , Q1 conducts and RY1 gets energized which in turn disconnects TR1 anode from supply then water Pump stops. when water drops below ST1 . Q2 turns off and so as RY2 then TR1's triggered through its gate.
When water reaches ST1, +12V on ST3 conducts through water to ST1 making ST1 positive. But Q2 is PNP and it should not have conducted.

Allen
 

Picbuster

Joined Dec 2, 2013
983
It seems not logical to use DC as current will flow in one direction and electrolyse will occur.
The normal way is to use a alternating current ,earth free and capacitive coupled.
Or use the simple way a floater with two switches.
 
View attachment 105589
It seems not logical to use DC as current will flow in one direction and electrolyse will occur.
The normal way is to use a alternating current ,earth free and capacitive coupled.
Or use the simple way a floater with two switches.
What voltage is on the Anode and gate of the thyristor on the second time, Q2 is a pnp?

Put a 100 ohms resistor in parallel with the pump, and back emf suppression diode.
nothing changed :(
 
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