I've been working on setting up a aquaponic system, I have a 108 plant NFT(nutrient film technique) system that typically uses a pump that cycles on and off every 20-30 minutes or so and instead id like to split flow from my dual pump setup that runs 24/7, the pumps are check valved so even during one pump failure, water will still flow.
To get a reliable solution to control water flow. Fish tank water is never perfectly clean, and its full on nutrients that plants need. I'm thinking a solenoid valve will have reliability issues in the long term with frequent on off conditions especially with the less than ideal water quality. Im working with low pressure pumps, which might make a solenoid valve not function as well. i've seen that with pneumatic solenoids on a separate project.
Luckily its not a giant hose feeding the plants, its a 5/16id, 7/16od tubing maybe 3psi max, I'm thinking for reliability pinching the hose or lifting the hose beyond the pumps head pressure to stop the flow(not as compact to be a ideal solution). I know servos tend to have a low cycle reliability, especially jittering around impacting a non movable object. 100% humidity, potentiometer cycles/gear wear even getting 6 months would be iffy on a servo. I curious what sort of solutions and ideas popup here.
Ive been thinking about a cam roller on a stepper motor but they get hot and my green house is topping out at 130*f. A awesome solution would be something energized only during a state change of the flow. a gear motor could fit that but controlling the stop point would need to be dependable, I've seen geared stepper motors and maybe thats really the ideal solution?
anyone else seen any cool solutions?
Geared DC motors with encoders have the power and positional feedback of the servo and are much more efficient than a stepper. Also the (optical or magnetic) encoder is more resistant to humidity than a pot. If the encoder is on the motor shaft, its resolution is multiplied be the gear ratio.
You can get electric valves that can do proportional opening and closing and only need power when they are moving. I'm not sure how resilient they are when the water isn't clean though.
A manual 90 degree on/off valve could be driven by a stepper and again could be set up to only pull current when moving.
The pumps that runs 24/7, runs a settlement filter basically removes large stuff, and circulates the system, also creates a backup areation via spraybar. 12 hours a day the sand filter kicks in. In my 110 gallon sump has a wild frog he slips through my fish net at the moment. Not really a ideal environment.
I had a garden hose solenoid valve fail on regular tap water out of the spigot in less than 6 months.
On electric valves, I haven't searched alot but ones by us solid where brass with a product contains lead warning or stainless not sure the alloy they used but 304 is food grade but will rust, and 316 isn't food grade. Kinda made me think twice about those.
Many aquaponic setups use different methods than nft, some are constantly flooded with areation in the water, or bell syphons in a flood and drain setup.
The nft system came with a pump that is known to fail. For reliability I just wanted to use my more reliable dual pump setup.
It seems some products exist called pinch valves. That might be the commercial solution.
Many operations would have a full time staff
I must have read bad information I heard it was cause 316 had chromium, but 304 has it too :-). I'm glad you were hear to correct me lol those stainless valves are looking ideal now as long as they close they can drip and that should be fine
Check the Asco series of valves:
I believe the H022 versions are potable water safe.
They come in many versions though, and while the one I have linked is 1/4"NPT, they have other sizes too. Some of the valves are NEMA 4X. They also have 24V, possibly 12V solenoids too.
And as mentioned above, 316 is more corrosion resistant than 304, esp for chlorides/salt and is used in food applications.
I use a normally closed, power off, solenoid valve that operates on the same V's as the motor. That way I only send motor V's to the motor and the valve opens at the same time. Power the motor off the valve closes. Been working great for 3 years.
but ones by us solid where brass with a product contains lead warning or stainless not sure the alloy they used but 304 is food grade but will rust, and 316 isn't food grade. Kinda made me think twice about those.