Semi Automatic water overflow controller

[Prashant Zingade]

Hi All,

I created latch circuit to start water pump manually and stop Automatic, in that I'm facing issue when i touch probe of wire by hand circuit start Automatic. Im using 12v 1Amp SMPS power supply.

How to reduce sensitive ?

Please help.

Circuit diagram attached.

 

[Harald Kapp]

SW 1 is for manual start,
SW 2 is for automatic stop, right?
Try adding a capacitor from tha base of Q1 to ground (0 V) to reduce sensitivity to noise

 

[Prashant Zingade]

Thanks for reply.
Yes. Sw1 to start n sw2 to auto stop.
Ok i will try it and get back to you.

 

[Prashant Zingade]

Also I notice that when I use 9v 500ma power supply it work good. But when I use 12v / 1amp supply its become more sensitive.

What will be the value for capacitor to Q1 base and ground.?

 

[Alec_t]

I would suggest adding a pull-down resistor of ~100k between Q1 base and ground to ensure the base is never 'floating' at an ill-defined voltage. Q2 could benefit from a ~100k pull-up resistor to the +ve supply to prevent possible leakage currents from causing spurious setting of the latch.

 

[Prashant Zingade]

I would suggest adding a pull-down resistor of ~100k between Q1 base and ground to ensure the base is never 'floating' at an ill-defined voltage. Q2 could benefit from a ~100k pull-up resistor to the +ve supply to prevent possible leakage currents from causing spurious setting of the latch.

Ok thanks i will try it.

 

[Prashant Zingade]

I would suggest adding a pull-down resistor of ~100k between Q1 base and ground to ensure the base is never 'floating' at an ill-defined voltage. Q2 could benefit from a ~100k pull-up resistor to the +ve supply to prevent possible leakage currents from causing spurious setting of the latch.

Capacitor is not required between Q1 base and ground ?

 

[Harald Kapp]

I would suggest adding a pull-down resistor of ~100k between Q1 base and ground to ensure the base is never 'floating' at an ill-defined voltage.

Q1 is pulled down, weakly though, by R2 and RL1. An additional resistor of ~100 kΩ may decrease sensitivity.
A capacitor will reduce sensitivity to noise (AC).
You may have to add both. Give it a try and play around with values to optimize the result.

 

[Prashant Zingade]

Added both 100k and 10uf/25v capacitor between base Q1 and ground. Circuit latch for 2 second and discount again.

Pl help.

 

[Alec_t]

Did you also add the pull-up on Q2 base?

 

[Prashant Zingade]

Did you also add the pull-up on Q2 base?

No that pull up not tried yet. I will try and update .

 

[Prashant Zingade]

No that pull up not tried yet. I will try and update .

It is working now. Thank you.

One more help. Can we add dry run protection in this circuit so that water pump will shut-off when no flow of water in pipe.

 

[Alec_t]

You could add a 'supply missing' switch in parallel with SW2.

 

[Prashant Zingade]

You could add a 'supply missing' switch in parallel with SW2.

I did not get you for 'supply missing switch'. Will you please elaborate.

 

[Harald Kapp]

'supply missing switch'

A switch that is activated when there is no supply of liquid to the pump. this switch in parallel to SW2 will stop the pump when the liquid supply is missing.