voltsOO6
Electrical
- Nov 1, 2006
- 9
I am an electrical engineer working for an A-E which designs all sorts of facilities. I’ve had all kinds of experience in lighting systems, fire alarm systems, power distribution, and telecom systems, etc.. My controls experience is some what limited especially in dealing with PLC’s.
I have a project where I have to compare the height of two hangar doors and stop a controls operation if one has moved farther than the other. I have proposed to do this with a rotational encoder on the motor shafts calibrated to measure the heights and encode it into a voltage or current. The existing controls are mechanical relay type. Therefore I have to send the encoded information into a PLC. The PLC must be programmed to compare the two elevations and then send out a stop signal to the existing mechanical relay controls.
Since I don’t deal with PLC’s much, how would something like this typically be spec’ed out.
My assumptions are 1) design a ladder diagram showing all existing relay logic and where the output of the PLC will be input into the existing relay logic to accomplish the desired operations, 2) Also, write a sequence of operations indicating how the entire system needs to be operate together, 3) Get input from a PLC manufacturer or PLC rep. as to a recommendation of a PLC, and 4) Use this recommendation as the guide to write bid specifications.
This seems to be all that needs to be designed on put on drawings as I perceive it.
As far as the PLC issues such as a) Check loss of state on power outage, b) check for the need of a signal delay, etc.; I assume that the specifications above would require that the supplier/assembler/control panel manufacturer would design/check this based on the functions that the system have to operate.
Man that was a mouthful. Any tips, ideas, guidance?
I have a project where I have to compare the height of two hangar doors and stop a controls operation if one has moved farther than the other. I have proposed to do this with a rotational encoder on the motor shafts calibrated to measure the heights and encode it into a voltage or current. The existing controls are mechanical relay type. Therefore I have to send the encoded information into a PLC. The PLC must be programmed to compare the two elevations and then send out a stop signal to the existing mechanical relay controls.
Since I don’t deal with PLC’s much, how would something like this typically be spec’ed out.
My assumptions are 1) design a ladder diagram showing all existing relay logic and where the output of the PLC will be input into the existing relay logic to accomplish the desired operations, 2) Also, write a sequence of operations indicating how the entire system needs to be operate together, 3) Get input from a PLC manufacturer or PLC rep. as to a recommendation of a PLC, and 4) Use this recommendation as the guide to write bid specifications.
This seems to be all that needs to be designed on put on drawings as I perceive it.
As far as the PLC issues such as a) Check loss of state on power outage, b) check for the need of a signal delay, etc.; I assume that the specifications above would require that the supplier/assembler/control panel manufacturer would design/check this based on the functions that the system have to operate.
Man that was a mouthful. Any tips, ideas, guidance?