beginner, need information

[Guest the_coco]

Hello, I’m a beginner in PLC technology. I have to try to develop an application for an HVAC system. This application should use by anybody in the company after to configure each system. My idea is to make an Excel application, as data entry to select that the system must do and program directly the PLC, because for each application all the device are not used. My questions are: 1) because I have programming experience and to be update easily by anyone, we want program in ST or FBD or SCL, but I don’t know which software I can use ? 2) I want know if my idea about excel is possible? If I have to pre-program the logic and after use an other soft to update the configuration by DDE, OPC ,activeX..? 3) Do you know it’s possible to have something like “starter kit” from some manufacturer, or a package not too expensive which I can program in ST /FBD/SCL? I saw some software : Isagraf, step7 Cx-programmer, cimplicity but I know idea which one is the best for me? Thank a lot for your answer. Nicolas Internship student - PLC beginner

[mick barrett 0]

Hi, you need to be very clear in what you'r proposing to do. I suggest you write a clear and simple description of the project, produce a flow chart from that description. This will give you a clear focus and also the I/O count which in turn will determine the size of the plc. I f a lot of user interaction with the HVAC system is required you might consider using an HMI . If you e-mail those details to me I'll be glad to assist. Regards, mick ----- mickbarrett@oceanfree.net

[Sleepy Wombat 27]

What type of adjustments are you talking about...???? In a HVAC system generally a user need only access to the Setpoint for a Zone. The deadband around the setpoint is usually sorted out on site and is fixed programmed in the logic. How complicated is the HVAC control, generally standard ladder logic should suffice, but hey that depends on who you want to be able to change it and also do you want to give them access to the code to anyone ? You would be the first they point the finger of blame at if the system stuffs up after they decide to have a play around....of course it was working correctly before...... As mick barrett says define the project a bit more and we would be more than happy to offer advice and scenarios...

[Guest the_coco]

I try to be more specific. I have an HVAC with several device, sensor, but each user doesn’t need all. For example: 1fan , 1 damper, 1 heater or 2 fans, 1 damper So I want to be able to program somekind of PLC according to the specification of the customer and this programmation has to be done by a production operator. The idea is the operator fill in an VB application ( for excel or not) and to finish he push an button “programming “ . This operation must upload in the PLC (so change the PLC code) this specific logic without the logic for the device, which has not been chosen by the customer. Normally, we don’t need to modify the PLC code after. I want use Excel or another application as an front-end for my application to change code in my PLC. I want know, if it’s possible to do it? For the number of I/O, we’re not completely sure for the moment, but it should be around 40-50 I/O. I hope it ‘s more explicit. I’m sorry for my english, but I’m not an english person. Nicolas ----------------------------------------------- internship french student --PLC beginner

[KinK 0]

It is possible however not easy. what u are trying to do is change the actual program that is running in the PLC. From the sounds of it your application does not sound to complicated. I know that this is going to sound bad but I need more info. Tell me more about the application how many sensors what type of sensors, what are you controlling. what do you hope to achieve. by giving us this info we can probably come up with a very good solution. Peace

[Sleepy Wombat 27]

You say that you want to programme the PLC via Visual basic.....I think you have a terminology issue..... What you can't do in any easy sense is to program, actaully code the PLC ladder logic, compile it and send it to the PLC. HOWEVER what you can do is to allow excel to adjust values in a PLC that will affect how the PLC will react/perform to certain contraints.... For example, Excel could be used for the start/end times of the Fans, what devices to come on together etc.... In this case the PLC is coded with a set program with adjustable values. Excel will need a communication active X plugin to allow comm's to a PLC etc... For an Omron system I would look at the CJ1 PLC and CX-Server Lite, which is a program that exposes communication to the PLC via Active X. Alternatively you could download the Omron Hostlink VB demo from the download section, which shows you haow to write the comm;s driver.... I hope that this is more then enough info to get you started....