I would like to use Raspberry Pi (preferably "Zero") as a platform to control the opening and closing of solenoid valves as well as control two BLDC motors. A separate part of the system will have a heater attached to a RTD thermistor and a controller with SSR. The only interaction with this part of the project will be an output/switch to de-energize the heater if the flow sensor from the motor output shows a flow less than the threshold of 1 CFM (for heater protection).
I have four NormalClosed valves (work function) and two NormalOpen valves (exhaust - labelled "a" and "b") with everything else the same. 24VDC direct acting solenoids. Each of the four NC valves will have its own tactile momentary switch to open the valve. The motor is a Micronel U71HL with integrated electronics; also 24VDC (datasheet attached). When powered up, the motor will produce 1 CFM and all output will go through the two NO valves. When one of the NC valves is energized, one of the NO valves needs to be closed; no change in motor. When two of the NC valves are open, both NO valves need to be closed; no change in motor. When three NC valves are open, both NO valves remain closed; motor RPMs increase to yield 0.5 CFM increase in flow (1.5 CFM total now). When all four NC valves are open, both NO valves remain closed; motor RPMs increase to yield 0.5 CFM increase in flow (2 CFM total now). The system needs to work the same whether the two open valves are 1 and 3 or 2 and 4 or whatever combination. The easiest way to think about it is that there needs to be 1 CFM minimum at all times, either being used (one or more of the NC valves opened) or exhausted (through one or both of the NO valves).
My questions are whether this can be done fairly simply (if 0, then RPM X; if 1, then RPM X; if 2 then RPM X; if 3, then RPM 1.5X; if 4, then RPM 2X) or something similar? What would need to be in place to deal with the NO/NC operation? Could it be as simple as (if 0 NC, NOa and NOb open; if 1 NC open, NOa open and NOb closed; if 2 NC open, NOa and NOb closed; ...etc.).
I will also have another, cheaper BLDC motor without drivers connected to five valves. One will be exhaust (1 CFM) and the other four will need to have 1 CFM flow whenever they are opened. They will open/close in tandem with the previously discussed valves. Eventually, the airflow from the two motors recombines to cool the air, with a ratio of 1:2 hot:cold. Because I need a driver anyway, could we remove the integrated electronics (use a different, cheaper motor) and control both with a dual H bridge Driver IC?
There are a couple misc. things left out, like kill switches to disable the valves if no slide is in the heating chamber. I would also like to monitor the flow sensor and have an emergency K thermocouple monitored in case the RTD thermistor or temp controller fail.
When you quote, please estimate both hours of work as well as a basic timeline estimate for the project.