Pneu 03 — Two-hand press cycle

Briefing

A pneumatic press has two start buttons far enough apart that the operator needs both hands, so neither hand can be under the ram. The press cylinder is double-acting: DOWN_SOL drives the ram down, UP_SOL brings it back up. Reed switches report the top (RETRACT_LS) and the bottom (EXTEND_LS) of the stroke. Rules: both buttons together start the down stroke. They must be pressed within 500 ms of each other. If the second hand is late, or one button is tied down with tape or a wedge, nothing moves and FAULT_LAMP lights until both buttons are released. Letting go of either button during the down stroke sends the ram straight back up, and so does reaching the bottom. After a stroke the press waits for both buttons to be released before it accepts another cycle. Training material. Follow your site procedures, local electrical code and the manufacturer's instructions. Lockout/tagout and a qualified person are required for real equipment. A real two-hand control is a safety function built from certified safety hardware, not from ordinary PLC logic.

Objectives

• Both buttons pressed together: the ram comes down
• One button alone starts nothing
• A second button more than 500 ms late starts nothing and lights FAULT_LAMP
• Releasing either button mid-stroke sends the ram back up
• After a stroke the press waits for both buttons to be released; a tie-down fault clears once both are released

I/O Table

Your program will be tested against:

All test cases run automatically when you submit. Assertions are hidden until you pass.

1. #1Both buttons within the window → ram comes down

   A, then B 200 ms later, both held

2. #2One button alone → nothing moves

   A single button never starts the press

3. #3Second button 0.7 s late → no press, fault lamp on

   The 500 ms window has closed

4. #4Let go of one button mid-stroke → ram goes back up

   Either hand releasing ends the down stroke and starts the return

5. #5Hands held through a full stroke → returns and waits

   The press needs both buttons released before the next cycle

6. #6One button tied down, then the other → fault; release both → clears

   A tie-down is refused and the fault clears when both buttons are released

7. #7After a cycle, release and press again → comes down

   A second cycle starts cleanly

8. #8B first, then A within the window → ram comes down

   The order of the two buttons does not matter