Help count down decade

[victoria]

Please help me to modify an up/down counter with a count down cycle of from 9 to 0 and not from F to 0.

I have already succeeded in building the circuit with count up cycle of 0 to 9 avoiding A to F.

The relevant section of my logic circuit work is attached.

I am a mechanical Engineer and a beginner in logic.

I want to simulate the Spillway Gate operations of the Victoria dam, Sri Lanka with a logic circuit project.
The purpose is to demonstrate the working of the electrical relay circuits to amateur staff.

The system

There are eight Spillway gates.
Each pair of gates is raised or lowered in four steps automatically without the presence of operators.
Start of each gate operation is triggered by the appropriate water level sensed with a float operated limit switch.
Stopping of each gate operation is triggered by a gate operated limit switch when the required gate position is reached.
The sequence of operations is programmed into the electrical relay control circuit.
The output commands are sent to the hydraulic pump motor contactors and the hydraulic solenoid valves to operate the gates.

My plan for the logic circuit project

Arrange the inputs digital water level meter, gate position meters and out puts motor contactors and solenoid valves on the computer screen.
Simulate the meters to increase or decrease.
When an operation level is reached on the simulated water level meter mimic starting the gates according to the control logic.
When a programmed gate position is reached mimic stopping the gates by changing over the motor contactors and solenoid valves on screen.
Changeover of all the inputs and outputs are to be indicated virtually on the screen with seven segment meters and LED’s etc.
All relay operations are to be indicated on a different screen with LED's etc.
The operation start or stop meter values are to be input into the logic diagram
When the simulated increasing or decreasing meter readings are equal to the programmed values the logic operation is triggered.

I expect to ask for more help in future.

Thank you for reading my request.

[Hans Cadans]

Hello Victoria,

Maybe I can help you. In the past I've placed an article about making a library of electronic circuits.
In this library you will find several useful circuits, among them different counters

You can find this library on page 2 of this forum.
Maybe it is necessary to replace your counter by the one found in the lib.

I hope, this will help you
Feel free to ask me, if anything is not clear to you

Best Regards
Hans Cadans

[victoria]

Dear Hans Cadans,

Thank you very much for the offer to bail me out!

I have downloaded the library and am going through the counters. I feel I have found what I want. I will comment after using one of your circuits or ask for more help.

Thank you again - Victoria