Stagehand Pro 4: Interlock Inputs

Pin	Description
1	+24VDC
2	Forward Interlock Input
3	Reverse Interlock Input
4	+24VDC
5	All-stop Interlock Input
6	0VDC (COM)
7	External Fault Input
8	Ground (Earth)

The Interlock Connector provides four (4) sensor inputs that can interrupt motion to avoid collisions.

Two machines may present a hazard on stage when they obstruct each other's path. The interlock inputs allow the Stagehand to sense an external obstruction and abort motion if the path is not clear. Interlock faults are shown on the Stagehand Display, and within the Spikemark software, to easily identify the culprit when motion stops unexpectedly.

Switches wired into the Interlock Connector are often wired Normally Open (N.O.) leaving the circuit open until the switch is activated by a scenic element moving into a safe position.

When automating a lift with a trap door, the lift should not move upward until the trapdoor is fully open. In such a scenario, a limit switch can be physically affixed to the trap door to sense the position of the door, but the switch can be wired to the Forward Interlock input of the lift to prevent the lift colliding with the trap door.

The Interlock Connector can also be used in conjunction with a Safety Interlock Box - Pro 4 to monitor 4-wire safety sensors such as sensing edges (aka astragal switches) or pressure mats. Both types of sensors can improve the safe operation of stage lifts.

Forward Interlock

Forward movement is interrupted unless +24VDC is sensed on pin #2 of the Interlock Connector. If motion is interrupted, either clear the obstruction or temporarily override the interlock signal by plugging in the Interlock Terminator that was shipped with the Stagehand Pro 4.

The Forward Interlock can be used much like a Forward Limit, but rather than limiting forward motion based on the position of the machine powered by the Stagehand, the Forward Interlock senses the position of another machine or scenic element.

A switch wired into the Forward Interlock could detect when a trap door is fully open, signaling it is safe to move a lift forward (up).

Reverse Interlock

Reverse movement is interrupted unless +24VDC is sensed on pin #3 of the Interlock Connector. If motion is interrupted, either clear the obstruction or temporarily override the interlock signal by plugging in the Interlock Terminator that was shipped with the Stagehand Pro 4.

The Reverse Interlock can be used much like a Reverse Limit, but rather than limiting reverse motion based on the position of the machine powered by the Stagehand, the Reverse Interlock senses the position of another machine or scenic element.

A switch wired to an access door for a lift could detect when the entryway is closed, signaling it is safe to move the lift reverse (down).

All-Stop Interlock

Both forward and reverse movement are interrupted unless +24VDC is sensed on pin #4 of the Interlock Connector. If motion is interrupted, either clear the obstruction or temporarily override the interlock signal by plugging in the Interlock Terminator that was shipped with the Stagehand Pro 4.

A pushbutton can be wired into the All-Stop Interlock as an enable button for a lift. Unless the button is depressed, no movement is allowed.

External Fault Input

Both forward and reverse motion will be interrupted unless pin #6 & pin #7 are connected on the Interlock Connector. This signal indicates that there is an electrical fault outside of the Stagehand preventing motion. The intention is to detect when a thermal overload relay has tripped on a single motor, when multiple motors are being powered by one Stagehand (e.g. a turntable being spun with multiple Revolver machines).

Interlock Terminator

Interlock Terminator

The Interlock Terminator ships with the Stagehand Pro 4 and should be plugged into the Interlock Connector whenever the Interlock Inputs are not being used. It can also be installed temporarily to defeat an Interlock Fault to drive the machine clear of an obstruction, provided it is safe to do so.