Delayed Automatic Forward Reverse Motion of Overhead Crane Driven by a Motor

This is another situation that requires the overhead crane to rest for a while upon reaching both of the rail. After a pre-determine time the overhead crane will re-start in the opposite direction.

The control circuit of this system is shown in Figure 8. Two times TR1 and TR2 are connected to the limit switches Y and X respectively at terminal 3.

The terminal no. 1 of the instantaneous contacts TR1(1-3) and TR2(1-3) are connected to the terminals no. 3 of the limit switch Y and X respectively. The delay contact TR1(6-8) and TR2(6-8) are connected to the contacts R(13-14) and F(13-14) respectively.

Supposing the overhead crane is moving in the forward (right) direction that means, contactor F(A-B) is at energized and contactor R(A-b) is at de-energize condition. When the overhead crane reaches the right end limit and touches the limit switch Y, the contact Y(1-2) of limit switch Y will open to de-energize contactor F(A-B). This will bring the overhead crane to stop moving in the forward right direction and it will remain at stand still for a pre-determine time set by timer TR1. Also the contact Y(1-3) of the Y limit switch will close to de-energize timer TR1. The instantaneous contact TR1(1-3) will close instantly to maintain TR1 continously energized.

After the pre-determine time set by TR1, the delay contact TR1(6-8) will close to energized contactor R(A-B). This will cause the overhead to start moving in the reverse (left) direction. At this point the connection of limit switch Y contacts Y(1-2) will open and contact Y(1-3) will close.

When the overhead crane reaches the left and it touches the limit switch X, the contact X(1-2) of limit switch X will open to de-energized contactor R and timer TR1. Instantaneous contact TR1(1-3) will open. At this point the overhead crane will stop moving in the reverse (left) direction and it will remain at stand still for pre-determine time set by timer TR2. Also the contact X(1-3) of the X limit will close to energized timer TR2. The instantaneous contact TR2(1-3) will close instantly to maintain TR2 continuosly energized. After the pre-determine time set by timer TR2, the delay contact TR2(6-8) will close to energize contactor F(A-B).

When the contactor F(A-B) is energized, it will cause the overhead crane to start moving in the forward (right) direction. Immediately after, the connection of contact X(1-3) will open and contact X(1-2) will close again. Timer TR2 will remain energize because its instantaneous contact TR2(1-3) is maintain close. Timer TR2 will be de-energized when the overhead crane reach the right end limit and touches limit switch Y.