Seeking help from PLC experts for programming! ! !
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There are 4 fans used to cool the gas exiting the compressor. The control logic is as follows: 1. If the temperature is above 55°C, the first fan is activated; if the temperature remains above 55°C after 2 minutes, the second fan is activated, and so on, until all 4 fans are running. 2. When the temperature is below 45°C, shut down one fan; if the temperature remains below 45°C after 2 minutes, shut down the second fan, and so on, until all 4 fans have been shut down. I would like to ask the experts how to program this on a PLC?
The temperature is set with a high value of 55°C and a low value of 45°C. When the high value is reached, the first motor is started via the start interlock; after it starts, a delay of 5 minutes occurs. If the high value still persists at that point, the second motor is started via the same interlock mechanism, and all motors are started in this manner one after another. When a low-level signal is detected, the last motor in the startup sequence is shut down as a form of shutdown; a 2-minute delay is applied after this shutdown. If the low-level signal persists, the second-to-last motor is shut down as part of the shutdown sequence, and all motors are stopped in sequence. The start interlock and stop interlock can be included in the motor operation conditions.
It’s not difficult; there are two conditions in total, four outputs, and 8 intermediate aids are used. It’s very simple to code with STL.
But shouldn’t we consider the situation where the motor fails and cannot start?
Typical sequential control, but faults of the fan must be taken into account, along with manual and automatic control
Experts, write a program – let’s continue the discussion!
Well, when written by experts, it seems simple, but there are probably many aspects to consider when implementing it, such as faults and manual operations
Before starting the fan, check whether the equipment is faulty and whether it is in automatic mode; if not, proceed to start the next one automatically
It would be best to mention what model of PLC you are using; this will be more helpful for everyone. The following factors should be taken into consideration: 1. Hand brake； 2. Fault ； 3. Do not keep the first fan running for long periods of time
1. First, create a manual/automatic control area JMP/JMPE; use M1~M4 to directly activate Y1~Y4. 2. For temperature comparison: if SP > SPH, then M5 is turned ON
For typical sequential control, it’s sufficient to write it based on the design concept of relay logic control.
It can be said that it’s not a very complicated procedure!
This is easy to program; a timer and accumulator will do, or data transfer instructions will work as well