I guess i should mention, i already have the system installed and working. i currently have 3 bags, a 400 and two 550's. currently I have 1 fill pump and 3 drain pumps. i will be changing the system to 3 reversible johnson ballast pumps. currently the whole process is manual. I have to flip a switch, wait, check the bags, wait, check the other bags, wait...... Im just trying to automate the process. My idea is to build a set of rules, a one touch button to fill certain bags. The idea behind this is to create different shaped wakes behind the boat for doing different activities, wake boarding, surfing, skiing, etc. Just for a background on me, I'm still pretty new with the Arduino but have programmed int he past, Im a DIY kind of person, i work on everything from home projects (tile, masonry, electrical etc) to automotive restoration(cars and motorcycles, engine rebuilds painting etc) and actually am a Linux admin for my daily grind. I've heard a ton of good ideas so far but i think they are kind of getting out of scope, ha ha
dave-in-nj:
there are multiple types of flow sensors.
a weir tube measures the height if the fluid in the tube, based on time of flight, you can calculate or monitor the flow rate.
you can have a set volume fill, then dump. that is a one way device. maybe (think h-bridge to alter destination)
like fill a five gallon bucket, then drain it. tipping bucket rain gauge ??? monster style.since water is non-compressible, the density will not change under pressure. an orifice at pressure will pass a known quantity. so you could control the pressure discharge of the pump through and orifice and calculate time to determine quantity.
you could use a positive displacement pump, much harder than some of the options, but might be a deal on e-bay.
as for the possible flow sensor, you can use a flow sensor on the pump, then alter the source and the discharge. (With all the H-bridges we do to control electrons, a couple valves to control water have been mentioned earlier. : )
I think the big questions are if you have a huge budget and how long you want this to take.
a garden hose sensor with diverter valves (h-bridge) would be pretty simple and pretty accurate, but could take a long time.a fire hose sized valve/sensor would be pretty costly !
If i get what you are saying about the pressure, i think that makes sense. From what i gathered, you are saying slightly restrict flow to keep a steady amount of pressure to get a more actuate reading? I could see that working. Currently the system is all ran from a single 3/4" inlet and a single 700gph pump. This method takes FOREVER to fill all 3 bags, and not to mention i plan on adding another front bag to help even the weight, so this would take even longer. I plan to upgrade to 3, 1" inlets (4 when i add the additional front weight) and 4 johnson reversible pumps. (or if i can come up with an automated selector to have a arduino controlled Y valve, that would save money as well.. I think i just need to get something in place and play with it. Im currently waiting for my flow sensor to come in, and i will create a mock environment where i can test the ideas out. Thanks everyone for the comments!