Just thought I would share my recent efforts with building some equipment. My winemaker friend had a problem with pumping out his primary ferment tanks where he often overflowed his barrels. I guess when you run a small winery there are lots of things distracting you and those mistakes can eventually add up to real money. He made a circuit with two stainless steel probes that would be inserted into the bung hole of the barrel and when they got wet would indicate that the wine had reached a certain level. This would trigger a relay that would cut the pump. I am impressed with his work on the equipment including designing the circuit, making a printed circuit board and finding the components to do the logic. The problem with the design is measuring liquid conductivity is not highly repeatable. This equipment is a bit fickle. I looked for a way to better measure liquid level. There are quite a few methods. I found a level sensor that is a float with a switch but it seemed difficult to sanitize. Also capacitance sensors are used but I did not feel like studying how to interface to it. The surprising solution I found while reading some trade magazines is an optical liquid sensor. This sensor uses an LED that transmits infrared light that is reflected by a prism back towards a photo detector. When the sensor is in air, the light is reflected back to the detector, but when the prism gets wet, the angle of light refraction changes and the light no longer reflects back to the detector. Ingenious! I tweaked his circuit to accept this sensor change and the level detector now works like a champ. The optical liquid detectors I am using I found on eBay. There are other sources but they can be spendy depending on the options desired. I thought it was a surprising solution and wanted to make winemakingtalk users aware of it.
The biggest challenge is getting the level detector into the bung hole along with a pump nozzle. It is a squeeze. Many level detectors would work but for that one requirement.
