Will A Photocell Light Resistor Have A Significant Different In Measurement between light seen above water and light seen 1-2 feet below water? I'm thinking it will have a different measurement because light reflects off water and there is also internal reflection underwater. I'm trying to make a diving submarine that signals a green led to light up when the sub surfaces. I'm thinking a photocell light resistor will do the job. Are there any other sensors good for this purpose? thx
How about two electrodes separated by a few centimeters which are connected to a CMOS circuit?
The idea being that when submerged, the water will create a relatively low resistance path from one electrode to the other since CMOS has very high input impedance, it will be easily able to detect the difference in resistance when submerged and surfaced.
EDIT:
Come to think of it, you could probably just use a 555 astable for the oscillator, then after the rectifier feed that to the ADC of the Arduino.
Some experimenting with the time constant (smoothing) of the rectifier will be required but should be easy enough to get going.
I'd need more direction on how to build that, but it is a good idea.
Start by making two probes (tea spoons or similar) with one end stuck into a cork or a piece of putty/play dough.
Now connect one probe to the Arduino supply (assuming 5V) and the other to A0 (ADC input).
Write a simple sketch to continuously send the ADC value to the serial port.
Now without touching the actual metal spoons, stick them into a container of water and note the difference in readings with the probes in and out of the water.
You may find that using a 555 oscillator will yield better results (and stop corrosion over time due to DC) , but try the simple "probes" first.
Something like this:
I'm trying to remember the name of a sensor using total internal reflection.
It consists of a conic section, where in, say, air, a light shining up will be reflected back down, but in water will escape and not reflected back down.
But will the "cleanliness" or salinity of the water not influence the reflections?
Ok I'll give it a try. thanks for the ideas.
UnoDueTre:
But will the "cleanliness" or salinity of the water not influence the reflections?
Minimal.
The difference in optical density between fresh and salt water will be far less than between air and water.
Since the sensor measures light loss, either the light escapes due to the lack of TIR in water, or it is absorbed by mud or dirt. As long as the water (mostly) falls away from the sensor on surfacing, TIR will re-establish.
Sounds an interesting sensor but wonder if it will be easier to build than two metal probes.
me too. I wonder how that would be designed. What is the sensor called?