Hello,
I built a custom semi-automated pressure test station. It basically allows a tech to place an assembly in a fixture, then use a joystick to move the fixture to the run position (Slide 1), another joystick to lower a "Cup" over the assembly (Slide 2). The rest is manual. They turn on a compressed air supply (Through a regulator), start a bench timer, stabilize for 7 minutes, write the starting pressure, shut off the incoming air valve (Like filling a basketball), start a 30-minute test to see if the pressure drops, then write the ending pressure reading. Then they vent off the air manually by opening an outbound valve, drive the joysticks the other way to first lift the cup off of the test assembly, and then return the fixture to the load position.
Now that I have proven the station works, my boss told me to put together what I would need to fully automate it. I have years of PLC experience, but I am working against a very limiting budget to get caught up in an off the shelf PLC plus pertinent programming software price in a place that has almost zero PLCs.
I would like to use an Arduino product to control this station and a bit more functions:
Relay outputs or outputs to relays...
Allow for a cycle start input (Then once that happens),
use a proximity sensor to indicate to the controller that the fixture is in the load position and another sensor to indicate that a part is present in the fixture. If either case fails, the cycle doesn't start.
move the fixture to the run/test position (Basically activate a valve to move a slide.)
another 2 sensors on that end to verify the fixture is present at the run position and a part is present in the fixture.
Move the other axis to lower the cup onto the part
2 more sensors on this slide to know the cup is raised fully or lowered onto the part (Test position). The slides are hard stopped, so they only move to one or the other end.
If the cup is down in the test position and there is a part present, turn on a valve to start the air flow to the part,
start a timer (Hopefully built in by way of a real time clock) to first run the 7-minute stabilization phase, then shift to an actual (another timer) 30-minute test time.
Display the starting pressure, when the 30-minute timer starts
Display the final pressure when the timer reaches 30 minutes.
open a valve to vent off the air
move the slides, in sequence, back, so lift the cup out of the way first, then return the main slide to the load position.
Maybe even have a pass/fail function on the display based on an allowable leak rate for the 30-minute test.
I would also require an input for a safety relay tied to an (emergency) E-Stop palm button, that would interrupt the cycle at any point, and stop everything right where it is sitting when the E-Stop is engaged.
I wanted to make sure the details of the whole sequence are well defined.
What model Arduino products would best work as a control solution?
I will get the 2-way valves, and 1 3-way valve for the air pressure on /off/ vent, pressure sensor and a digital to analog converter if that's necessary to input the pressure, position sensors, safety relay and details.
Are there peripherals to a specific Arduino product that I would also need?
Power supply? Anything else to aid in outfitting this station for automatic operation?
I would appreciate any constructive feedback you might provide in helping me find the best solution for the project described here. I'm asking you what I should use, being unfamiliar to your products. Someone recommended I look into using your hardware.
Thank you
