Pool cleaning robot water sensing?

[ForumUser1]

Hi All,

I recently repaired a pool robot (Maytronics) and during post repair test noted the device would shut down after going through a test sequence. Indication of shutdown was by drive and impeller motors stopping, and the small LED on the PCB changing from a slow flash to a rapid flash. I could restart with the on/off switch on the power supply (120 AC to 29 VDC).

There is no other water sensing input to the control board ... my assumption is the controller senses the amount of power required to run the impeller motor and allows normal operation if it sees an amount indicating water drag, but shuts off if it sees too little or too much. Does this sound correct?

Thanks!

 

[Nigel Goodwin]

Yes, I use a similar current monitoring technique in one of my products, although in my case it's to detect if a solenoid is plugged in or not.

 

[ForumUser1]

Thanks, Nigel - I was flummoxed about this and then it hit me that the PCB was smarter than I was.

Apparently the impeller motors of these commonly fail and the amp draw increases so controller just shuts it down - I'm assuming too little current draw is how the device ensures it doesn't overheat outside the water?