the water circulates back into the tank after it passes through the spindle motor
i just need an alarm to show if the water stop flowing.
like to bring on a warning light or horn.
what i think can also work is if i can mount a vibration sensor on the submersible pump.
to indicate if the pump stop working.
i am sure a temperature sensor can also work .
what will be the best way to add one?
and what will be the simplest way to do this. and what temp sensor do you recommend for this
paul

 

off the shelf flow sensors is really sounding like a much better idea for this project, trying to use a temperature sensor to detect when the water stopped flowing would be bad for the bearings and such, since they have gotten to the point of heating up to increase the temperature of the spindle, you want to detect if the flow stopped right away without causing thermal damage and wear on the mechanics of the spindle, so a flow sensor would definitely do that for you.....

 

That's a good point BMorse, although the bulk of the heat will be from the windings (very little heat will come from thebearings by comparison) and a temperature sensor on the body of the spindle would I believe give a pretty good indication of coolant failure.

That's quite a common system in industry, due to the difficulties of coolant flow sensing. They just check for overtemp condition.

OK, if a coolant flow sensor MUST be used, you could make a "bobble sensor" like the ones on the old gasoline pumps, where the coolant flow makes a bead bobble about from the incoming liquid jet below the bead. Then detect the bead movement using an optical sensor or a magnetic hall sensor.