Slack cable detection for stage equipment

The S880 snap-action switch is actuated if the lighting suspension gets jammed.

Each scene requires different lighting. Above the theatre stage, lighting and sound rigs move up and down. A slack cable switch detects if the lighting suspension gets jammed or stuck.

How do microswitches detect a slack cable?

The cable is wound onto a drum with a spring mechanism. Normally the weight of the lights pulls the drum down. If the cable becomes slack, e.g. because a light gets caught in the stage sets, the spring pulls the drum upwards and actuates the microswitch. This opens the signal circuit, and the controller stops the drive.

Why was the S880 snap-action switch chosen?
  • Miniature size: 20 × 9.3 × 6.6 mm (L x H x W)
  • Self-cleaning contacts
  • Positive opening operation of the break contact (VDE approved)
  • Suitable for safety-relevant applications (Machinery Directive, ISO EN 13849)