this is my first time using Arduino, then please be patient with me
I want to apply an Arduino system to disinfect with additional sodium hypochlorite solution water entering a tank.
Water contains already chloride but not enough to prevent recontamination. Therefore, my goal will be to apply a chloride sensor measuring the water entering the tank and a dosing pump that supplies the desired amount.
For example, if the water entering the tank contains 0.3 mg/L of FRC (Free Residual Chlorine) and I need 0.5 mg/L, the dosing pump must enter 0.2 mg/L.
We strongly recommend that you spend some time learning the fundamentals of Arduino before starting a project like this. Work through the simple examples that come with the program development software (the IDE): learn to blink an LED without using delay, read a switch, a voltage, a sensor, control a motor, in order to learn the language and special features.
Otherwise expect endless frustration.
Of course you are forgetting things in the above list. Most obviously, a professional quality dosage pump and a tank mixer, so that the concentration readings can be believed. You may also need a pH sensor and a means of adjusting or compensating for pH (see the manual for the chlorine sensor).
Furthermore, you need backup sensors. You cannot possibly risk equipment failure, and the introduction of toxic levels of hypochlorite to your drinking water.
Strongly agree with the above .You also need to look at liability issues too if ( other) people are going to drink this stuff .
You may need to look at other chemicals too ( nitrates ?)
I wouldn’t personally do this sort of project with an Arduino - it’s a hobby machine , you don’t want wires falling out and the dosing pump going flat out!. You certainly need to look around at what is commercially available , what standards or approvals are these made to and what is required .
I do really understand your concerns but unfortunately I have searched around for already-made systems but none of them is able to insert the right amount of chlorine depending on the amount entering the system.
Systems that are commercially available are usually intended for pool system when the desired amount of chlorine is kept constant.
Other chemicals are not a big issues since they are below WHO guidelines.
I know that I need some experience first and I am already watching tutorials and reading examples.
In case you have more suggestions, please tell me.
DodoPat:
I do really understand your concerns but unfortunately I have searched around for already-made systems but none of them is able to insert the right amount of chlorine depending on the amount entering the system.
Systems that are commercially available are usually intended for pool system when the desired amount of chlorine is kept constant.
Dosing pumps for drinking water have exactly that arrangement.
Used to do the service on them.
I would also have a sensor(s) in the tank measuring the residual in the tank, that is a double chek on the input dosage and to help in case the incoming organic load sucks up the chlorine
just to review.
a sensor in the tank to verify the levels of chlorine in the tank. this is a must as any runaway control the one before your system, or your system, can cause changes.
the dosing pump. here, I would not oversize.
the flow sensor is a hobby device. it is only accurate at higher flows.
If possible, I would also look for a mixing tank. a smaller tank that allows for mixing before it enters the main tank.
or mixing blades in the pipe. these look like a helix and cause turbulence in the water to create mixing.
the cost of the sensor is really high, so getting multiples may not be an option easily afforded.
That said, after the proper amont of mixing distance in the pipe / mixing tank. a second sensor to make sure the mixed levels are in an acceptable range. this could require 10-20 meters of pipe so it many not be easy to do.
I would also add a dispaly to the Arduino and also an SD card to record the readings. if your unit runs wild for a few hours, then stops adding, then the supply brings the tank back to normal, and only then you look. you would not know of the transient problems.
In first builds, having lots of data helps two things. One to figure out what is happening to pin point problems, and #2 to re-assure you that things are working as expected.
I am not sure of the dangers of a run-away control, but if it drinking water and it is too low, then you can get sick by NOT addressing the problem.
