Stop 'bouncing' input from float sensor

Question

I'm trying to resolve an electro-mechanical issue to do with a water fill solenoid, that is triggered by a float valve. The problem is as the water approaches full, the float bounces causing the solenoid to rapidly switch on and off. Not great on solenoid or the water pipework that gets hammered.

Instead of adding expensive delay off timers, I was hoping to add a capacitor to the simple circuit to delay the closing of the solenoid. 1 second delay would be great, 3 or more would be better! The system runs on 24 Vdc, the relay controlling the solenoid draws around 100 mA.

Any help with sizing the right capacitor or if there is a better way would be much appreciated.

Answer 1

Position the float sensor so that the incoming flow presses down on it.

Answer 2

Use two float switches combined with a relay. The lower switch turns the solenoid ON, while the upper switch turns it OFF. So you have a hysteresis.

^{simulate this circuit – Schematic created using CircuitLab}