brad.wynn
Member
Hello there! First post, so don't be too hard on me!!
I have done a few simple programs with the Square D line of smart relays - Zelio. I am getting pretty comfortable with ladder logic and the hardware and wiring comes naturally for me.
I have now taken a small step up to an actual PLC, but at the baby end of things... I am working with a Schneider Modicon M171, which is geared toward HVAC controls. I have written 3 programs that are currently deployed in a test location. One is a temperature control with two stages of heating and an ignition sequence.
The second is a small program to change the states of the programmable LED indicators on the display to correspond to different events during the heating cycle.
The last program is a high limit and low limit alarm contact closure.
There are a few features that I would love to implement, but I am about at my wits end trying to figure this out.
The first has to do with changing the setpoint in my heating program. The user would like to be able to have an up button and down button that directly changes the value of the temperature setpoint. I have written the program to do this, but with one hitch. The variable for temp_setpoint is stored in EEPROM, so as not to be lost on a power outage. For the life of me, I cannot get the program to write to that variable. There is a function called "SysWrite..." something or other that is labeled as being able to do such, but adding it into my logic causes a "PLC Run Error" when I try to compile and send to the hardware. Anyone have any hints?
The next thing is that when the above is sorted out, I want the display to switch to the setpoint for a few seconds when an adjustment button is pushed, then back to showing current room temp. I have not found a function that does anything with the display?
And lastly, the customer is leaning toward a stand alone monitoring system for these remote sites. It is a cellular system that has digital and analog inputs. I can utilize my digital output alarm mentioned earlier to trigger an event on the monitoring system. What would be even better, would be to send a 5-20ma signal to the monitoring system that matches my room temp value. Again, wiring is not a problem, but the logic to accomplish this is my achilles heal.
Any help is greatly appreciated! I hope I can continue to learn and become a master of the PLC!!
I have done a few simple programs with the Square D line of smart relays - Zelio. I am getting pretty comfortable with ladder logic and the hardware and wiring comes naturally for me.
I have now taken a small step up to an actual PLC, but at the baby end of things... I am working with a Schneider Modicon M171, which is geared toward HVAC controls. I have written 3 programs that are currently deployed in a test location. One is a temperature control with two stages of heating and an ignition sequence.
The second is a small program to change the states of the programmable LED indicators on the display to correspond to different events during the heating cycle.
The last program is a high limit and low limit alarm contact closure.
There are a few features that I would love to implement, but I am about at my wits end trying to figure this out.
The first has to do with changing the setpoint in my heating program. The user would like to be able to have an up button and down button that directly changes the value of the temperature setpoint. I have written the program to do this, but with one hitch. The variable for temp_setpoint is stored in EEPROM, so as not to be lost on a power outage. For the life of me, I cannot get the program to write to that variable. There is a function called "SysWrite..." something or other that is labeled as being able to do such, but adding it into my logic causes a "PLC Run Error" when I try to compile and send to the hardware. Anyone have any hints?
The next thing is that when the above is sorted out, I want the display to switch to the setpoint for a few seconds when an adjustment button is pushed, then back to showing current room temp. I have not found a function that does anything with the display?
And lastly, the customer is leaning toward a stand alone monitoring system for these remote sites. It is a cellular system that has digital and analog inputs. I can utilize my digital output alarm mentioned earlier to trigger an event on the monitoring system. What would be even better, would be to send a 5-20ma signal to the monitoring system that matches my room temp value. Again, wiring is not a problem, but the logic to accomplish this is my achilles heal.
Any help is greatly appreciated! I hope I can continue to learn and become a master of the PLC!!