Move water using raspberry pi

Question

bit of an amateur looking for some advice. Have done quite a bit of web searching but want to validate my proposed design. The project is a water control system using a raspberry pi.

I have a water purifier with a tank, and i need to move the water to 4 printers when they need water. However, the printers contain a water tank so i need some kind of precision.

I tought about this design :

Thanks to the precision needed, i don't think i can use the gravity to move the liquid. That's why i tought about using a pump. But i think that might cause some troubles. Will it be troublesome to active the pump when all valves are closed ? if i open the valve one at a time and then active the pump will it work ?

Maybe another design will work better ?

I need advice ...

It works like this :

the printers send a message in a database . For the moment i send the error message to a raspberry pi with sockets .

Now i want to use these messages and when one of the printers need water , i want to refill it automatically. When i receive the message , i know that the printer need, for example, 4L of water. That's why i need a pump so i know i need to active the pump for like 30sec and approximatively 4l of water will be refilled.

But i'm afraid, il will cause problems with the pump and the solenoid in series ...

Answer 1

As Wouter said, this may not be directly an electrical engineering question, but it does involve electrical control and since I have a fair amount of experience with fluid control, I'll answer and let the question be moved if necessary.

First, you mention that some level of precision is needed, but don't specify it. What precision does the liquid need to be transferred in? The reason for choosing a pump vs. a gravity feed generally is due to where the fluid supply has to be placed, or cost, or flow rate needs. Precision is not normally a reason to choose a pump vs gravity. If the printer water reservoir has a sensor that indicates when it's full then you shut off the water supply when that sensor is activated.

If the printer tank doesn't have such a sensor and you can't retrofit one, then you could use a flow meter (disclaimer: I am affiliated with that site) in line with the piping to measure the water that's being dispensed into the tank and stop the valve/pump appropriately

Next, if you are using a centrifugal pump, such as a small impeller pump, then they are generally quite tolerant of being run with the output closed off. Positive-displacement pumps such as syringe pumps, not so much. Using a pump gives you flexibility in where to place the water supply. However, if you can put the supply overhead, then gravity-feed solenoid valves will control the water flow accurately without needing a pump.

As for control from the Pi, its outputs won't be able to drive solenoid valves or pumps directly. You'll need to have the Pi control a DC solid-state relay or a FET driver that can handle the load.