Non-contact liquid level sensor - battery powered.

Hi there,

I need a simple led-based notification for when a noxious liquid has reached a certain level in a plastic container. The containers vary and all can be removed so I need an external sensor such as the capacitive ones you can buy.

I would like to do this in an arduino and have researched the forum cap sense entries to find a similar project but no answer. Will a sensor say, 10mm (1/2") away from a water-based liquid contained in a plastic bottle be an easy/reliable task for a simple cap sense system? If so would I need to create a sensor that had a ground pad beside/beneath it as the liquid won't be grounded itself?

Thanks, in advance, for your advice.

Colin

Use ultrasonic "ping" sensor

Thanks, but wouldn't that just bounce off the plastic/glass bottle surface? I don't have access to an open port in the top or side.

Will a sensor say, 10mm (1/2") away from a water-based liquid contained in a plastic bottle be an easy/reliable task for a simple cap sense system?

I use these (got used ones for free from discarded equipment) and although they work very well, their range in air for (pure) water level sensing is only about 5 mm. There might be some that work up to 10 mm.

Yes, I have use those off-the-shelf sensors before and they do work very well but I was hoping for a simpler, smaller, lower-power design maybe based on the capsense idea so I can build something from an ATtiny and a few other components. When the liquid level is reached the dielectric will obviously change more dramatically than with a finger so I would assume what I'm seeking should be doable.