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[Jon Wallace via Personal_Submersibles]

 Alan describes a pretty reliable system.  The pressure sensor might be the most expensive part.  If you can find a solenoid valve for the pressure you are expecting then the computer could activate that as well instead of relying on an open orifice to release the pressure.  Teensy 4.0 would be an alternative for the nano.  An Rpi would be better because it's easy to log the results but they are very difficult to find these days because of the chip shortage.  I can help with the programming as well.
Jon

    On Sunday, November 13, 2022 at 06:00:53 PM EST, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  
 
 Hi Hank,You would need an electronic pressure gauge for feedback to a computer (Arduino) & a display for visually monitoring what was going on. The Arduino turns the hydraulic pump on via a solenoid switch; when you get to the required pressure the program
turns the pump off & perhaps you could have a nipple with a small orifice that releases the oil back in to the sump via a tube, dropping the pressure in the process. The oil would be coming out of this nipple while you are pressurizing, but it's just a simple solution for the depressurizing faze.Once the pressure drops to a set level the program cycles again. The Arduino counts each cycle and stops at the end. The display shows pressure and cycle number.You would possibly need to adjust the program depending on how it operated & maybe have pwm control over the motor speed if it pressurized too fast.BTW I had some SS electronic pressure gauges made up with threads compatible with 1st stage regulator ports.I just finished a project for counting the anchor length on a boat, so a little bit familiar with what's needed on the computer side.The project below uses an Arduino Nano & a cheap 16 x 2 display. Probably around $25- of components there.Alan



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  On Mon, 14 Nov 2022 at 4:46 am, hank pronk via Personal_Submersibles<personal_submersibles at psubs.org> wrote:   Hi submarine friends.  I just completed a pressure test to failure on our Cast Epoxy port.  The port was 1 inch by 8 inches OD.  An acrylic port this size is rated to fail at 2,100 feet sea water.  My Epoxy port failed at 1,225 psi or 2,744 feet fresh water.  
  Any ideas on how to make a hydraulic apparatus to cycle the port  from zero to operating depth in my chamber?  
Hank
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