Hi Guys,
I am a student at Swinburne University and trying to learn PLC Programming. Currently trying to program smart control for Condensers as a project. The scenario is that a company has 5 Condensors that are old and they are to be replaced with a set of new condensors with VSD Drives controlling fan speed whereby the old ones didn't have this ability.
So I'm trying to set up to concurent Step Control Sequences that will help smoothen the process of migration as the old condensers get decomissioned over time, replaced with new ones.
Being new to PLC programming as well, I dont quite know how to set up a step and sequence relationship(Focusing for now only on the new VSD Fans)
For example if I have 5 new condensers and I am trying to vary the fan speed and turn on and off certain condensers based on pressure increasing and decreasing.
At the moment the logic I have so far works like this.
step 0 - all fans are off
step 1 - if pressure is increasing + VSD fan is available than start first fan at min speed
step 2 - enable fan PID
step 3 - if fan speed goes above 20Hz + Pressure increasing + another VSD fan available, start next vsd fan and continue till all are on (after all vsd fans on, engage sequence logic to start old condensers)
step 4 - if fan speed less than 18 HZ + Pressure decreasing, stop last fan started (first stop any old condenser fans still running using its logic sequence)
step 5 - go back to step 0 on power fault etc
I am happy with the above steps, however I am running into trouble implementing it.
I have come up with a system where a tag is assinged a value for the steps by moving a step number to the tag if conditions above are met. my problem however is with getting the vsd condensers to come on one at a time and waiting for them to speed up to setpoint before turning next one on.
so I have a tag which says which condensers are available. and if any condenser out of the 5 is avaialable it adds 10 to the sequence number and subtracts 10 from the sequence if its not available. so I have value of
0 = 0 condensers avail
20 = 1 avail
40 = 2
60 = 3
80 = 4
100 = 5
so step 1 and sequence= 20, check if cond1,2,3,4,5 is avail and turn on. ( since 20 means only 1 will be available, I can work systematically through them all and turn the 'one' on)
but my logic breaks when i do
step 1 and sequence = 40 (so 2 condensers available) - how can I find out which out of the 5 condensers is avail and turn it on, than wait for its speed to be above 20 before turning on the second condenser (after first finding out which one it is)
same issue again when 3, 4 and 5 condensers available. how do i uniquely identify the 5 condensers and possible combinations without ending up with 32 unqiue combinations and conding them seperately
I hope I am making sense here. Feel free to ask me any questions and I will try clarify.
Basically I am stuck with trying to find a way to identify which out of the 5 condensers is available to turn on and turn it on one after the other, after waiting for conditions of the step 1 to be met and the speed of previous one is above 20.
if i didnt have to turn them on one after the other it would be simple as i can check if all 5 are avail and turn on the ones that are.
any help or advice would be much appreciated. This is doing my head in for the last week
Found a way to export the little logic I have written to see if it helps you help me so I've attached it. Not sure if there is a better option. Using RSLogix 5000
I am a student at Swinburne University and trying to learn PLC Programming. Currently trying to program smart control for Condensers as a project. The scenario is that a company has 5 Condensors that are old and they are to be replaced with a set of new condensors with VSD Drives controlling fan speed whereby the old ones didn't have this ability.
So I'm trying to set up to concurent Step Control Sequences that will help smoothen the process of migration as the old condensers get decomissioned over time, replaced with new ones.
Being new to PLC programming as well, I dont quite know how to set up a step and sequence relationship(Focusing for now only on the new VSD Fans)
For example if I have 5 new condensers and I am trying to vary the fan speed and turn on and off certain condensers based on pressure increasing and decreasing.
At the moment the logic I have so far works like this.
step 0 - all fans are off
step 1 - if pressure is increasing + VSD fan is available than start first fan at min speed
step 2 - enable fan PID
step 3 - if fan speed goes above 20Hz + Pressure increasing + another VSD fan available, start next vsd fan and continue till all are on (after all vsd fans on, engage sequence logic to start old condensers)
step 4 - if fan speed less than 18 HZ + Pressure decreasing, stop last fan started (first stop any old condenser fans still running using its logic sequence)
step 5 - go back to step 0 on power fault etc
I am happy with the above steps, however I am running into trouble implementing it.
I have come up with a system where a tag is assinged a value for the steps by moving a step number to the tag if conditions above are met. my problem however is with getting the vsd condensers to come on one at a time and waiting for them to speed up to setpoint before turning next one on.
so I have a tag which says which condensers are available. and if any condenser out of the 5 is avaialable it adds 10 to the sequence number and subtracts 10 from the sequence if its not available. so I have value of
0 = 0 condensers avail
20 = 1 avail
40 = 2
60 = 3
80 = 4
100 = 5
so step 1 and sequence= 20, check if cond1,2,3,4,5 is avail and turn on. ( since 20 means only 1 will be available, I can work systematically through them all and turn the 'one' on)
but my logic breaks when i do
step 1 and sequence = 40 (so 2 condensers available) - how can I find out which out of the 5 condensers is avail and turn it on, than wait for its speed to be above 20 before turning on the second condenser (after first finding out which one it is)
same issue again when 3, 4 and 5 condensers available. how do i uniquely identify the 5 condensers and possible combinations without ending up with 32 unqiue combinations and conding them seperately
I hope I am making sense here. Feel free to ask me any questions and I will try clarify.
Basically I am stuck with trying to find a way to identify which out of the 5 condensers is available to turn on and turn it on one after the other, after waiting for conditions of the step 1 to be met and the speed of previous one is above 20.
if i didnt have to turn them on one after the other it would be simple as i can check if all 5 are avail and turn on the ones that are.
any help or advice would be much appreciated. This is doing my head in for the last week
Found a way to export the little logic I have written to see if it helps you help me so I've attached it. Not sure if there is a better option. Using RSLogix 5000