Design of Safety Device for Spindle Coolant

I'm hoping for some guidance on a design idea, that will hopefully lead me down a path where I learn some more advanced concepts in LinuxCNC. Here's the deal:

The Problem:
My Chinese spindle is water-cooled, but depends on a garden pump that is cheap enough to fail at any time. Loss of coolant flow is not an immediate problem, but running for 30 minutes might be.

The Goal:
Create a system that provides audible/visible warning on the UI if coolant flow to the spindle stops, and sets a timer that will command the machine to a graceful halt if no intervention within x minutes.

Design Idea:
Use an inductive sensor on a column of coolant that drops out of detection range if the flow stops or is impeded below the rate the column drains through a pinhole outlet. Full flow allows coolant to simply overflow into the tank below the sensor

It's an approach I have seen in industrial wet dust collection systems as part of NFPA requirements for explosive metallic dusts -- basically interlocking the system to shutdown if there is not enough water present to ensure the non-obliteration of a city block.

For LinuxCNC application, I am not sure where to start. I have an inductive sensor tested and ready to go on the Mesa 7i76e I'm using, defined in HAL with:

net H20sense hm2_7i76e.0.0.input-04

...and that's as far as I've gotten.

What is the best toolchain for such an approach? I'm hoping to get suggestions that can guide the study path of components I'll need to master to pull this off.

I'm using Axis UI, but I'm open to other suggestions if there are approaches that work better in other UIs.

KISS Keep It Stupid Simple

What is your problem? Heat.
So keep it simple and mount a simple thermoswitch with a loud buzzer...
You could connect it to an input. m5c

Mike

Connect a LM35 temperature sensor to one of the 7i76e analog inputs. I think full scale of the input is 36 volts so you might need a signal amplifier to increase the voltage from 5 volts up to your signal voltage (say 24 volts).
www.ebay.com.au/itm/LM358-Weak-Signal-Co...?hash=item3af4aa934b

I have been thinking of doing this to turn a cooling fan on and off.

I think the wcomp component will let you create an error threshold to trigger a on/off signal. You could feed this into your estop chain using estop-latch.

That's along the lines of what I'm thinking, Rodw. I'm still sticking with the flow sensor over a temperature sensor, because if the temperature starts to climb, I think it might be too late. I'm just concerned that the innards of the spindle could go critical before the exterior of the case elevates enough to trip on temperature alone. That's why the failsafe do-not-exceed timer is my first instinct.

I've been looking at some ClassicLadder examples, and now I'll give wcomp and estop-latch a read-thru also -- thanks for those pointers. I'm also looking at modifying an example of a floating UI window that currently displays spindle speed and current draw -- I think I can modify that to link to the signals for binary waterflow sense. Maybe even also add a temperature sensor as a interesting secondary, to act as an absolute limit to trip e-stop if the audible/visible warnings are missed and the temp starts to go haywire.

Some of the carving designs I'm looking at might take 3 hours+ to complete. My reason for the UI link is because I will be monitoring over remote desktop at times, and I want the audible/visible cue when flow stops so I can make some decisions: intervene and halt the job, check to see if the job will finish quickly, or even install a backup pump. A buzzer at the machine won't provide that.

"Simple" by itself is not among the design objectives I also want a challenge that will lead down the path of discovering more advanced techniques, and I'm looking at this a lab experiment as well as a practical addition to the machine.

Thanks again!

something like this is also a possibility:

www.ebay.com/itm/Water-Flow-Sensor-Switc...-6L-min/262704070815

$4 with free shipping?? Wow. That's a much cheaper solution than my inductive sensor. I'm going to check that out.

Thanks!

I did look at a similar flow sensor but be aware it outputs a pulse so you probably need to use a encoder or MPG input to decode it.