Practice missions
Practise in
0 XP
Practice missions
Mission 67 · Pro PLC programming exercise

Stop dead or slow down

Make the E-stop a category 0 stop and the gate a category 1 stop: brake first, then cut the power.

Cut the power at once on the E-stop (category 0). On the gate, brake the arm under power first and cut the power once it has stopped, or after 1 s at most (category 1).

Training only. This is not a certified safety system. On a real machine these rules run in a safety relay or a safety PLC, designed and validated to ISO 13849-1 or IEC 62061.

This mission is part of ProTry the full course, every mission and the expert challenges free for 7 days. No card needed.
The 3D robot safety cell this mission runs on Pro mission
Test replay

The gate brakes, then cuts the power

Test 1 of 5
Set by the testChecked by the testStep 15 of 15 · 1.5 s
Level
Advanced
Time
About 40 min
Reward
+500 XP
Rig
3D robot safety cell
Siemens editors
Ladder (LAD), SCL
Rockwell editors
Ladder, Structured Text
Beckhoff editors
Structured Text
Course stage
34. Safety lab 3: how to stop, and what to let through
Automatic tests

What the tests check

  1. The E-stop opens K1 and K2 and stops DriveRun in the same .
  2. The gate stops DriveRun at once but keeps K1 and K2 closed while the arm brakes.
  3. K1 and K2 open at Standstill, or after 1 s if Standstill never comes.
  4. An E-stop during a category 1 stop cuts the power at once.
  5. No reset or start until the stop has finished; then Reset and Start as before.
  1. Try it Use the buttons below the model and watch the rig respond.
  2. Test solution Every check runs on your code in one press.
  3. Replay If one fails, step through it one scan at a time to see why.
Why it matters

Where you’d see this on site

Drives on robots, saws and big fans often use category 1 stops. Braking under power stops a heavy arm much sooner than letting it coast.

Cutting the power is the simplest stop, but a heavy arm then coasts. With the gate already open, those seconds are when a hand reaches in. Category 1 uses the drive to stop it first.

Where you'd find thisKeep people out while the arm moves, and prove it every time

A robot stacks cartons inside a fence. A gate lets a fitter in, a light curtain lets the cartons in, and an emergency stop sits outside. Two contactors in a row cut the robot's power, so one that sticks cannot keep it running.

  1. InfeedCartons through the curtain
  2. PickRobot takes the carton
  3. GuardStop, reset, restartYou are here
  4. PalletSix cartons, then change
On a real site: places, parts and safety
  • Robot palletising and packing cells
  • Machine tending: robots loading presses and machine tools
  • Any guarded machine with a door, a curtain or an E-stop

Training only: this rig is not a certified safety system. Real safety functions run in safety relays or a safety PLC, designed and validated to ISO 13849-1 or IEC 62061.

IEC 60204-1 sets out stop categories 0, 1 and 2 and how an emergency stop must behave. Which category a machine uses comes from its risk assessment.

The sizes, timings and cutaways are teaching choices, not a drawing of any one real installation.

Keep going

Next in the course