timbo_uk
Member
I am starting to develop a project for a new control system for a solvent mixing system.
I will be using a Telemec HMI that is currently operating a monitoring system for the section after this mixing area. This is using the first comms port to a Micrologixs 1000 (DF1); I want to use the second port through DH485 to a second plc.
PLC choice from Micrologix range or PLC500. But cost to minimum (isnt it allways!)
32 Valves
11 Level switches
1 E-Stop (1st part hard wired, 2nd part of circuit to PLC for monitoring)
2 high speed inputs; I could multiplex this to 1 input as the flow meters never run at the same time.
My first problem is how "high speed" inputs do I actually need for the signal from my flow meters. The single pulses (1 channel) are theoretically up to 430Hz. I have scoped the flow meter during a normal flow and got this:
I can see the mark space ratio is short (about 10:1), so I assume I cannot just work from the pulse frequency. The pulses are 0.3mS each.
I have been trying to find out about the SLC500 high speed card, but that looks to be a single channel, and designed for encoders (ie 2 channel A and B).
I can see that I wont get away with a standard input with a minumum scan time of 1mS I would miss most of the pulses. The SLC500 card looks serious overkill!
Basically all I want to do is using recipies from the HMI batch different mixes of solvent into certain tanks as each level drops. EG. 5 litre batch from HMI, convert 5L to a number of pulses, subtract "x" amount of pulses to make "y" to allow for solvent flow after valve shut-off. Open valve and count pulses until count => "y"; then turn off valve...... and so on through all tanks.
There is a bit of cleverer stuff for detecting flow fail on one of the 6 solvents and water, this will then check which other tanks are not using that particular solvent and inhibit those from filling. This is one of the problems with the current system; should one solvent supply fail the entire fill sequence is aborted for the rest of the 11 tanks.
Can anyone give any pointers as to what I need to look for?
Thanks
I will be using a Telemec HMI that is currently operating a monitoring system for the section after this mixing area. This is using the first comms port to a Micrologixs 1000 (DF1); I want to use the second port through DH485 to a second plc.
PLC choice from Micrologix range or PLC500. But cost to minimum (isnt it allways!)
32 Valves
11 Level switches
1 E-Stop (1st part hard wired, 2nd part of circuit to PLC for monitoring)
2 high speed inputs; I could multiplex this to 1 input as the flow meters never run at the same time.
My first problem is how "high speed" inputs do I actually need for the signal from my flow meters. The single pulses (1 channel) are theoretically up to 430Hz. I have scoped the flow meter during a normal flow and got this:
I can see the mark space ratio is short (about 10:1), so I assume I cannot just work from the pulse frequency. The pulses are 0.3mS each.
I have been trying to find out about the SLC500 high speed card, but that looks to be a single channel, and designed for encoders (ie 2 channel A and B).
I can see that I wont get away with a standard input with a minumum scan time of 1mS I would miss most of the pulses. The SLC500 card looks serious overkill!
Basically all I want to do is using recipies from the HMI batch different mixes of solvent into certain tanks as each level drops. EG. 5 litre batch from HMI, convert 5L to a number of pulses, subtract "x" amount of pulses to make "y" to allow for solvent flow after valve shut-off. Open valve and count pulses until count => "y"; then turn off valve...... and so on through all tanks.
There is a bit of cleverer stuff for detecting flow fail on one of the 6 solvents and water, this will then check which other tanks are not using that particular solvent and inhibit those from filling. This is one of the problems with the current system; should one solvent supply fail the entire fill sequence is aborted for the rest of the 11 tanks.
Can anyone give any pointers as to what I need to look for?
Thanks