Electrical installation and pneumatics (DIN-compliant)
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Purpose
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- Ensure operator and bystander safety
- Provide deterministic, fail-safe shutdown behavior
- Comply with applicable DIN / EN machine safety principles
- Keep safety independent from software and firmware

Electrical installation
-----------------------

- Electrical system designed in accordance with:

  - DIN / EN 60204-1 principles
- Separate grounded electrical cabinet
- Segregation of:

  - mains power
  - motor power
  - control signals
  - sensor signals
- Use of:

  - main contactors
  - appropriate fusing
  - protective earth bonding
- All safety-relevant wiring implemented in hardware

Emergency stop (E-stop)
-----------------------

- Emergency stop system implemented as hardware-only
- Normally-open main contactor
- E-stop directly interrupts:

  - mains power to drives
  - control power where required
- No software involvement in E-stop behavior
- E-stop overrides:

  - Duet
  - ECU
  - Raspberry Pi

Pneumatics
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- Pneumatic system used for:

  - tool clamping
  - auxiliary machine functions
- Depressurization valve:

  - normally open
  - wired directly into shutdown circuit
- Behavior on:

  - E-stop
  - power loss
- Result:

  - automatic venting of pneumatic system
  - loss of pressure as safe state
- Pneumatic control logic not software-dependent for safety

Fail-safe behavior
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- Loss of electrical power results in:

  - drives de-energized
  - pneumatic system depressurized
- Safety chain behavior is deterministic and testable
- No single software fault can inhibit safe shutdown

Scope limitations
-----------------

- No software-based safety logic
- No safety functions implemented in Duet, ECU, or Raspberry Pi
- Safety system not affected by firmware updates