I am again asking for advice, and as always, I am grateful for any and all advice. A little background information about what I am doing and what I want to achieve. I have a main vessel and I have parameters (allowable bounds) for the PH level of the liquid in the container. I am looking to have two liquid injector systems for the vessel to keep the PH within the allowable bounds. While the vessel isn't supposed to be pressurized, it might be slightly, but it is mainly because the internal system needs to be completely sealed off from the outside. (highly susceptible to damage from the air)
For my current planned idea, I have two pumps and two three-way valves. When the PH has been out of bounds for an extent of time, it will start a pump, and push the respective liquid through the valve into a return line back to the container (to bleed the air off and establish a pressure once the valve switches to the container). Then the valve will rotate and allow some liquid into the main vessel, and then close back to the original return line state. A picture can be seen down below.
My main question for this is, is there a meter or something to only allow a certain amount of liquid into the main vessel? Or would the best way to approach this be to measure the total output for different durations of time and make a linear output approximation for how much to add? Is there a better way to approach this solution?
Thank both of you! I haven't dealt with pumps before much and didn't know of the peristaltic pump. I did some further looking and I am having trouble finding ones that use splined shafts. Is this peristaltic pump from Adafruit an example of a friction fit shaft?
Or Adafruit Item # 3910
Do you have a recommendation for finding a provider that has the splined shafts?
I will have an agitator stirrer rotating inside the vessel with a speed-controlled motor and I am targeting a range of 40-200 RPM (more than likely not that high though). I will have a PH sensor dangling from the topside and the PH sensor submerged into the main vessel solution.
Thank you again. I will try tomorrow searching under those terms a little bit more. I hadn't tried looking specifically at the stepper motor driven pumps, so perhaps that will be the key.
There are many more options that are more expensive, but I am currently in between the SEEED PH sensor and the DFRobot PH sensor (links to both are below). As for my setup, I am planning to have the motor on top of the vessel, with the agitator blades stirring the bottom 1/2-3/4 of the main vessel solution. I plan to either dangle the sensors into the top of the solution or mount them onto the bottom plate, but I do not want them to interfere with my stirring at the bottom of the solution.
I ended up going forward with the SEEED sensor, thanks for the information! The solution in the main vessel is a slurry of bio-ingredients that are decomposing in an aqueous solution of sorts.
I was looking for another sensor on Atlas, and I found they also sell dosing pumps. Do you think this one is one of the slipping kinds?
That is what I was thinking as well. I am looking to save costs, but not at the expense of one of these pumps going out. It shouldn't be used very often, but a single test run is approximately a month and I don't want to take a risk of it quitting on the home stretch of the test run. I don't have any data on how often it will need to kick on to keep the pH within bounds, but it shouldn't be run very often as I was initially told it could be manually injected if needed.
Does anyone know an easy way to measure RPM? I would like to use my main Arduino to do it, but I am afraid by trying to integrate it using a rotary encoder, IR sensor, hall effect, etc. that it will cause issues. Or is there a brushless motor and speed controller out there that can regulate its own RPM at an RPM setpoint for Arduino?
Are you going with the EZO-PMP pump/motor combination from Atlas?
It appears to use a DC motor coupled to the peristaltic pump head.
That device has its own custom serial uart (or i2c)communications protocol for dispensing. It's designed around volumes and times and manages the rpm in the background. It does not report RPM, but it's not clear why you would need it.
Depending on the application, you may want to go with a Stepper driven peri pump. Certainly for many hours of continuous dispensing, the stepper will have longer life than the brushed DC motor, but from the specs, it looks like the motor has a longer life in hours than the pump head.
Sorry, I was specifying measuring RPM for the BLDC agitator motor I will use to stir the main vessel solution and pump injection system's respective solution together. I should have been more specific beings the topic at hand was a peristaltic pump. I won't be measuring the peristaltic pump's RPM because I will measure the output and use a time interval for inputting a specific amount of fluid into the main vessel.
However, I will need feedback as for my agitator motor to keep it at a mostly consistent RPM. Does anyone know a simple method of getting this feedback? (thank you both for the response, sorry I didn't clarify!)
I will have an agitator stirrer rotating inside the vessel with a speed-controlled motor and I am targeting a range of 40-200 RPM
Can you supply some details on the motor and controller you will be using?
Typically the controllers will have some input for rpm. Why do you think that the controller will not do this job correctly?
Did you consider a stepper for the agitator, and why did you choose the BLDC? If the stepper can handle the torque and won't miss steps, the speed control is very simple
Will the stirrer face different loads, or is the torque requirement pretty steady? Are you going to vary the RPM based on some particular input? What is the tolerance on the rpm setting?
Sorry to be asking you more questions than providing an answer to your question, but understanding the big picture and the issues you are facing will help those trying to help you.
No need to be sorry on the asking questions part, all it does is ensure we are on the same page and you are being kind enough to help me.
I haven't chosen a motor and controller, yet. This kind of explains questions 1-3. I will be running this setup for a month at a time for several attempts, and I was shooting for a BLDC because of their extended life being brushless. One issue is I haven't found a controller that regulates the speed based on an RPM input, so I figured it would be up to me to supply the change in power or change in signal to meet my specified RPM. (I probably haven't been searching with the proper key terms and this could be why I haven't found one).
The torque requirement should be fairly steady. And yes, I probably should switch to a stepper, and I am not sure I have thought of that to be quite honest. I have been looking into it, and using the steps and specs of the motor I should be able to make one work perfect for this application. At this time I am planning on moving forward with a stepper, at this point I am just trying to estimate the torque needed to choose a motor.
