I have a system to drive two peristaltic pumps (labelled 12V, that draw 300mA) in a microscope in the lab in order to refresh the media of my cells for long term experiments. In the current setting I'm pumping 40mL/min, which is too much. I need to be able to control the flow-rate (lets say, in a perfect world, between 0.5ml/min to 10mL/min).
I am using a 2A 12V DC power source.
Pumps are in parallel. I have two 8 ohms resistors right before each pump (in each parallel branch). (it was my first try to reduce the speed of the pumping that's why they are there)
I also, now, have 4 paralleled 4ohm resistors right after the power source (I needed to drop the current for today's experiment and it was all I had nearby and I didn't want them to fume even though they are higher than 1.2watts, 6 I believe).
So my question. I want to have a way to regulate the flow. Potentiometers usually come in high resistance forms and low wattage (I found a few 100 \$ \Omega \$, and a 10 \$ \Omega \$ - 5W online. Should I use the 10 \$ \Omega \$ potentiometer?
Can I connect a potentiometer in parallel with the pumps trying to create a resistive voltage divider? However I don't know how to calculate the value to that potentiometer. Is this the best way to do it? I also can't to spend a lot of money on this.
I am concerned about temperature since the whole system (except the 12V power supply) is inside of a 37ºC enclosure to keep the microscope warm and the cells happy.
I saw this related post, but I have no idea on what values and pieces to use. Slowing Down a 12 volt pump with a potentiometer?
This is the state of the thing right now: