Canal Lock Sequencers

RIGHT SEQUENCER
SQI(Right_Array_I,1487,Local:1:I.Data,Cntr2)
SQO(Right_Arr_O,47,Hold_Right_O,Cntr2)

LEFT SEQUENCER
XIC(TEST)
SQI(Left_Arr_I,479,Local:1:I.Data,Controlling)
SQO(Left_Arr_O,31,Hold_left_O,Controlling)

Overview

This was a challenging program I wrote for CNTR 300. A lock moves ships between a low and a high water level by filling and emptying a chamber between two gates.

I no longer have photos of the panel, so I built this simulator from the program. It compares the lock’s inputs against the same tables on a fixed scan and shows every I/O point live, including which bit each step is waiting on. The machine is a model, and its timing is illustrative.

How it works

Two sequencers, one for each direction, compare the lock’s inputs against a table of expected states. When the inputs match, the sequencer steps forward and writes that step’s outputs to the gates, the water level valves, and the free signs.

Step	Ship from the left	Input	Output	Ship from the right	Input	Output
0	Wait for a ship	19	0	Wait for a ship	1027	0
1	Lower the water	23	8	Raise the water	1035	4
2	Open the left gate	150	1	Open the right gate	1289	2
3	Free sign on, ship enters	198	17	Free sign on, ship enters	329	34
4	Close the gate	71	0	Close the gate	75	0
5	Raise the water	75	4	Lower the water	71	8
6	Open the right gate	265	2	Open the left gate	134	1
7	Close the right gate	11	0	Close the left gate	7	0
8	Wait for the next ship	27	0	Wait for the next ship	1031	0

The sequencer table

I planned the sequencers in a spreadsheet, turning each step’s expected inputs and outputs into bits and then into the decimal values above. For example, step 0 on the left expects the left gate closed (1), the right gate closed (2), and a ship from the left (16), which adds up to 19. Masks of 479 and 1487 on the inputs, and 31 and 47 on the outputs, limit each sequencer to the bits it needs.

The saved rungs and tables are under Original program in the simulator, and they run unchanged. The simulator adds one step: when the direction changes, it returns the water to mid level, because the tables start a new direction from there and have no step that does it.