Time relay control of pneumatic control valve — II
Thread Content
I posted a thread before, aiming to use a relay to control the valve opening. Imagine: 1. When a signal is sent to the time relay, the relay begins to send instructions to the pneumatic control valve, causing it to open. Open to 10% of full openness, maintain for 10 seconds ； 2. After 10 seconds, the time relay sends another command to the pneumatic control valve, causing it to change its opening degree to 15% of full open, and this state is maintained for 10 seconds ； 3. After 20 seconds, the time relay sends another command to the pneumatic control valve, setting it to 20% of full open position, and this state is maintained for 10 seconds ； 4. After 30 seconds, the time relay sends a command to the pneumatic control valve to close it ； 5. Wait for the next signal to be received to activate the relay. I saw a programmable time relay online; I wonder if this relay can be used to implement this process. If that doesn’t work, what type of instruments should be used to achieve this goal? I hope everyone can help out a lot~!
This is program-controlled and can be easily implemented using a PLC.
What about programmable time relays? Is that possible? The main issue is that PLCs are very expensive
Such a high-end time relay will not be much cheaper than a PLC with a capacity of 200.
A set of PLCs can cost over 20,000 yuan, while programmable time controllers can be purchased for just a few thousand yuan; even adding a few analog output modules doesn’t increase the cost much
:It really puts the child in a difficult situation.
Why not use a PID regulator? Over a thousand yuan.
We use PID controllers. It’s 628, but the control valve has a delay of over 10 seconds. Our working cycle is very short, only 1 minute; such a long delay is a problem. We’re thinking about ways to address this
If the PID regulator does not function properly, it indicates that the PID parameters are not set correctly. These parameters need to be adjusted until stable control is achieved. To find the ideal parameters, some control systems require extensive tuning time; simply entering a few values is not sufficient. If the PID regulator does not function properly, it becomes even more impossible to achieve control using a time relay; when there is a long delay, the effect of differentiation should be introduced or increased.
We adjusted it, and even after the adjustment, it’s still 10 seconds – a very long time. PID was used at first, and since it didn’t work, other methods were considered.
A systematic approach is needed to view control: only by checking each element such as sensors, valves, PID controllers, etc., in terms of design, installation, selection, and calibration, can the root cause be identified. It’s not just a technical task; it also requires patience. Finding the root of the problem is the hardest!