Thanks for the ideas that were put forward.
A sump float switch in the water tank is good and will turn off the pump before it runs out of water.
Just outlining my problem. Rainwater tanks and 240vac Pressure pumps. The pump turns on and off as you flush a toilet or turn on a tap. It senses the pressure drop and starts the pump. When the tap is turned off the pump keeps going until its up to pressure, normally a few seconds. When a pipe breaks or and end comes off or some jerk (me) cuts it with a lawn mower without noticing it the pump will then run continously until all the water in the tank is empty and after that the pump seizes up.
So what I need is something to sense that the pump is running abnormally long, say half hour continuously, and then shut it of.
So to wait until the tank is empty to shut it off is no good , because here in Australia water is precious.
Also ease of connection. I was thinking of something plug into the power lead. Sensing the voltage drop when the pump kicks in so start a timing sequence of say a 555 timer and relay. Or an audio amplifier trigger that is "listening" and a timer circuit.
I have talked to a pump irrigation expert and he hasnt heard of any system but he said it happens all the time..
Anyway thanks for the ideas, keep them coming and a solution might be found together.
A sump float switch in the water tank is good and will turn off the pump before it runs out of water.
Just outlining my problem. Rainwater tanks and 240vac Pressure pumps. The pump turns on and off as you flush a toilet or turn on a tap. It senses the pressure drop and starts the pump. When the tap is turned off the pump keeps going until its up to pressure, normally a few seconds. When a pipe breaks or and end comes off or some jerk (me) cuts it with a lawn mower without noticing it the pump will then run continously until all the water in the tank is empty and after that the pump seizes up.
So what I need is something to sense that the pump is running abnormally long, say half hour continuously, and then shut it of.
So to wait until the tank is empty to shut it off is no good , because here in Australia water is precious.
Also ease of connection. I was thinking of something plug into the power lead. Sensing the voltage drop when the pump kicks in so start a timing sequence of say a 555 timer and relay. Or an audio amplifier trigger that is "listening" and a timer circuit.
I have talked to a pump irrigation expert and he hasnt heard of any system but he said it happens all the time..
Anyway thanks for the ideas, keep them coming and a solution might be found together.