Need a water sensor
w4fej
Posts: 264
In my R/C submarine project I want to be able to detect the presence of ANY water in the water tight compartment (WTC) and interface it to a Propeller. Don't need to know anything other than I've got some..
Any suggestions??
Mike B. - W4FEJ
Any suggestions??
Mike B. - W4FEJ
Comments
Depending on how deep you dive, this could be problematic. 35 feet is about one atmosphere (15 PSI) so if you don't presurize the compartment higher than the water pressure of whatever depth you're at, a leak could cause an actual increase in pressure if you are "at depth", or a decrease in pressure if you are near the surface.
Assuming you won't be doing loop the loops or barrel rolls with your sub, my thought would be to make a depression in the bottom of the WTC, have a couple of bare wires close, but not touching, and look for a change in capacitance. You could probably even do this with a small circuit board using a couple of closely spaced traces.
If you could tolerate some standing water, you may also be able to get by with a temperature sensor, assuming that the water would be cooler than the air in the WTC. (I'm from Wisconsin, and this would almost always be the case here...)
John R.
Separate question back at you:
What do you use for an antenna, and how deep can you dive (and keep control of the sub)?
John R.
Hi John.
The antenna will be a 1/4 wave vertical on the boat and probably something with gain on the control unit. The transmitter will be capable of up to 5 watts. The depth won't be much more than periscope depth. This isn't a reasearch vessel or anything, just a fun project I have been working on for several years. I re-did the whole electronics setup coming from the BS2P40 to the Propeller when I stumbled on to it. Just got back from a sheet metal shop to have the front and rear panels made.
I will be using 430 Mhz amateur band. The guys now using "regular" R/C gear have no problem controlling the boats down to 10 - 15 feet with something like 50 miliwatts on 72 - 75 mhz. Depends on the water. Salt water is the worst, pool water is better and fresh water the best.
I was hoping to find a sensor that was 5VDC or maybe 3.3VDC to just say HI, water, Low now water. Don't need temp, pressure or any of that. In fact I was going to install two sensors, one at the low point in the WTC and another just beblow the circuit board height. If the first one goes off then surface and head for shore. If the second one goes off, emergency blow all tanks and TRY to get to shore, other wise, go swiming!!
Mike B.
Rick
http://www.amazon.com/Rialco-84010-Flood-Sensor-1-Pack/dp/B000G1ME8E/ref=pd_cp_hi_3
http://www.amazon.com/Zircon-Leak-Alert-Electronic-Detector/dp/B00004XOVI/ref=dp_cp_ob_hi_title_1
Or for something more fun use:
http://www.amazon.com/Leak-Frog-LF001-Water-Alarm/dp/B000WMSTUO
Robert
Mike;
Thanks for the info on controls.
The concept of measuring capacitance (measuring R/C time) with either bare wires, or a small circuit board with adjacent traces should work off the prop. Look at some of the ADC routines and objects. (Look for something on how to read a "pot", and then substitue a fixes resistor (or trimmer) for the pot, and your two bare wires for the capacitor.
In concept, you set the pin as an output and "charge" the circuit. Then you simultaneously make the pin an input, and time how long before the pin goes low. Using the R/C Time formulas, you can determine the capacitance. In your case, you don't need to do any conversion, just determine what the readings (time) for "dry" and "wet" are, and use that.
Personally, I'd see this as more reliable than a mechanical "float" switch. In small sizes, these are usually done with a pivoting float with a magnet to activate a reed switch.
The plant moisture things I've seen use capacitance and/or resistance changes in the soil similar to the "bare wire" concept I mentioned above.
The suggestions for pressure and temperature were meant as other indirect ways of looking for water. Any type of sensor is going to be using some indirect means to see if water is present. Float switches don't really sense water, they sense mechanical movement of the float. Electronic moisture sensors are measuring the electrical properties of the soil (capacitance and/or resistance).
John R.
http://www.homesecuritystore.com/p-48-2800-water-sensor-switch.aspx
Mike B.
For $15 you're getting my two bare wires, plus the electronics to convert it to a 5 VDC on/off signal, along with some bulky packaging.
In additon to the money (not all that much), you'd also save space.
If you're interested, I'd be willing to work something up this weekend. I'm at work now, and have a tight schedule this week.
John R.
http://www.harborfreight.com/water-overflow-alarm-92334.html
Get one of these for $3 while you're there...
http://www.harborfreight.com/electronic-fly-swatter-40122.html
Sure John, I got nothing against saving money! lol. I also saw something at Lowes today for $12.00 that is battery powered that worked the same way, bridge across the contacts..
Mike B.
John R.
Good deal John, looking forward to seeing what you come up with.. Thanks again. In the mean time, here is a old pix of the hull in it's early stages. This will simply be a form that gets glassed over and then the hull gets cut apart and the foam removed. It is still in three parts if you look closely. Disregard the big goof standing next to it....oh, ... wait, ... that's me... :smhair:
Mike B.
Okay, this is admittedly an asinine idea, but consider it the beginning of a brainstorming session, perhaps get you thinking along less traditional lines:
Powderpuff the inside of your sub with a small amount of calcium carbide.
If any water touches it, it produces acetylene gas.
Test out one of Parallax's various hydrocarbon sensors to see if it will trigger on small amounts of acetylene gas. (Maybe try out the alcohol/ethylene sensor, for example.)
If effect, you will have a water sniffer.
Use too much calcium carbide, however, and you might have yourself an ocean-going acetylene bomb.
In any case, this is probably not the best idea in the world, but it might start you thinking.
http://www.hobby-boards.com/catalog/product_info.php?cPath=22&products_id=1544
The "leaf" sensor is a nice way of increasing the senstivity/capacatance of the sensor. It also can work with just a few drops hitting the leaf, it doesn't need to be submerged.
The question becomes, what do we really need in terms of sensor size/capacatance in order to be able to minitor it with the Prop...
John R.
No problem on the time John, the need is a way off yet. Still assembling the new control unit. Gonna try and "silk screen" the front panel when I get the nerve. Going to try and see if I can transfer the front panel graphic to a Tee shirt transfer and then to the aluminum/painter front panel. It will be really great if this works..
I like the looks of the leaf sensor. The WTC will be plastic and the sensor could lie face down on the "floor". Any moisture should be detected. The price is right as well.
I want to know right away if there is anything other than dry air in the WTC. If there is that means trouble and I want the boat on the roof like NOW!
Mike B.
I was working on a project where I accidentally measured the humidity inside a closed tube (not the goal and made my test runs curious) . I wonder if you could use a humidity sensor to tell if you were picking up water. As it sloshes, it should raise the humidity. You might have to temperature compensate.
Just a thought. ROVs are on my "2 year" project list so keep those projects moving.