For an indicator to light up when its gate opens, it must be wired to the Normally Closed (NC) contacts of the limit switch, which break the circuit when the gate hits the switch's actuator arm, instead of the Normally Open (NO) contacts. A type of limit switch with normally closed contacts is used on your refrigerator door to turn out the light inside when the door is closed.

The normally closed contacts are important for safety reasons when a gate is driven by an electric motor. They remove power from the motor when the gate reaches its limits of travel in either direction, so the motor doesn't burn up trying to drive the gate through a piece of steel or throw the gate out onto the floor.

The placement of a fully-closed limit switch is critical. If it is too far in, the gate will hit the side of the chute before it hits the switch, so it can pop circuit breakers or overheat. If the switch is too far out, the gate will never close completely, and grain can leak into the wrong chute.

Indicator lights on control panels are on the way out, being replaced by icons on computer monitors. The 3-D model shown has a monitor screen above it on the left side. If you click on the monitor with the mouse, it will move down to cover the indicator lights. The icons on this monitor, like those used in a real elevator, are made to physically resemble the gates they represent. They change position as well as color to show whether the gate is open or closed.

Notice that the icons give no indication of whether the gate is fully open (FO) or partially open. GIPSA does not require a fully-open indicator for most gates, because the grain goes to the same destination whether the gate is fully open or partly open. The elevator management also generally does not care if a gate is fully open, so fully-open indicators are uncommon.

NOTE: If the model does not appear below you do not have a VRML player installed.