Optical or Float Sensor

[TrueTricia]

Question for you guys.  I'm connecting my skimmer cup to drain into a waste water bucket from AWC so that the skimmate gets added to the old saltwater.  I've got a Neptune PMUP in the bottom connected to a drainage line.  I've also got an optical sensor at the top that tells me when the bucket is full.  So here's my question, I want to add a sensor to the bottom (in a PMUP stand awesomely printed by @brobak ) but I'm questioning what kind.  I have an optical sensor I can use or a float sensor.  My concern with either is that the skimmate will be thicker down at the bottom.  Will it obstruct an optical sensor?  Or will a float sensor get stuck?  Or am I being completely too paranoid?

[Origami]

Why do you need a sensor at the bottom of a waste bucket?

 

Neither sensor will work well in this application because a) The optical sensor works on the index of refraction at the interface between air and the material it's made from. That interface will be obstructed with skimmate scum on the surface; and, b) float sensor will not move freely. A better option might be to use an air pressure sensor like what Avast Marine has.

[Guest]

42 minutes ago, Origami said:

Why do you need a sensor at the bottom of a waste bucket?

 

Neither sensor will work well in this application because a) The optical sensor works on the index of refraction at the interface between air and the material it's made from. That interface will be obstructed with skimmate scum on the surface; and, b) float sensor will not move freely. A better option might be to use an air pressure sensor like what Avast Marine has.

 

I was thinking a sensor would be necessary to protect the PMUP pump from running dry.  This way when the waste is done pumping out, the pump automatically shuts off.  But your comments are exactly my concerns.  Maybe I just buy a new PMUP v2 that has the run dry technology....

[cpu933k]

You could test to see how long it takes to pump from when it is full to before it runs dry. Then set your programming to only run the pump for that duration when it is full. It won't be exact since the water/skimmate mixture will vary, but will be good enough to drain most of it and not run your pump dry.