What's the hardware I need to use LabVIEW PID to control some heaters?

[Top24]

The goal is to with LABView I control the temperature of 8 heaters and display it in graph, etc but I need th PID controler to control my output (my input is OK)

[johnsold]

You have indicated that this is a college project. It seems that you are a student.

Are you studying engineering of control systems? The emphasis on PID control would suggest that. Or, are you only interested in the temperature(s) of the plate(s) and the effects on whatever is mounted on the plates?  These are two very different projects but either of them can fit the descriptions you have provided so far.

The process for an engineering student: 1. Determine the requirements - temperature range, rates of change of temperature, time-temperature profile, accuracy and tolerance, mass and properties of the materials to be heated, power ratings of heating devices, safety requirements, cost requirements, and other constraints.  2. Perform the thermodynamic calculations to determine the power requirements. 3. Create a model of the overall system including the control process. 4. Design the control system to satisfy the requirements. Select appropriate components to implement the design. 5. Build and test.

The process for a science student who is studying whatever is being heated: : 1. Determine the requirements - temperature range, rates of change of temperature, time-temperature profile, mass and properties of the materials to be heated, power ratings of heating devices, safety requirements, cost requirements, and other constraints. 2. Find an engineer to do 2-5 above.

The impresssion I have from your posts so far is that you have very little idea of what the requirements are. And yet you have already specified that a PID control should be used. You have asked for help but have not provided the essential information that someone would need to provide useful suggestions.

Please provide the information so that we can try to help.

Lynn

[camerond]

What I meant is: Is this primarily (1) a project for you to learn how to run LabVIEW to create a PID controller from scratch, or (2) to control the temperature of your device? (Some of) The devices I sent you a link about can do PID control by themselves with just a serial input of the temperature setpoint and active bandwidth. But there's not a lot of LabVIEW programming needed and you don't have to set up your own PID schedule. If you can get sufficient power through them to heat your device, they will work. But, if this is supposed to be a project ti teach you a lot about programming different inputs and outputs and doing calculations in LabVIEW, it doesn't do a whole bunch of that.

Cameron

[Top24]

Hi again,

The thing is I don't really know all the requirements, I'm a trainee at a company (sent by my college in order to finish a project subject) so in the company they told me that I need to do everything in LABView, latter they told me that I need to use a PID controller to control my heaters, the steps 2-5 I'll do them latter and the step 1 I don't really know all the specifications yet...

Right now what I need to know how to do is in a new VI put a numeric control in whitch I put a temperature number and it goes to a PID then by anymean (which I still don't understood which) it connect's to my computer and my heater and the computer is controlling directly the heater... this is for testing because latter I'll have to control 8 heaters. Imagine a block diagram... I need to know what's bettween PID and the Heater and how to use it...

I saw some of you sent me some temperatures PID controlers to buy but from what I have understood so far I need to do my own 😕

Sorry about the messy question but it's really hard to ask for something that even I don't know what to ask.

Thanks for all the anwsers so far.

[Top24]

Hi again,

The thing is I don't really know all the requirements, I'm a trainee at a company (sent by my college in order to finish a project subject) so in the company they told me that I need to do everything in LABView, latter they told me that I need to use a PID controller to control my heaters, the steps 2-5 I'll do them latter and the step 1 I don't really know all the specifications yet...

Right now what I need to know how to do is in a new VI put a numeric control in whitch I put a temperature number and it goes to a PID then by anymean (which I still don't understood which) it connect's to my computer and my heater and the computer is controlling directly the heater... this is for testing because latter I'll have to control 8 heaters. Imagine a block diagram... I need to know what's bettween PID and the Heater and how to use it...

I saw some of you sent me some temperatures PID controlers to buy but from what I have understood so far I need to do my own 😕

Sorry about the messy question but it's really hard to ask for something that even I don't know what to ask.

Thanks for all the anwsers so far.

[billko]

That's like specifiying the type of vehicle you should use before you know what it's going to be used for.  You know you'll need to transport something.  Is it big?  Is it little?  Bumpy terrain?  Smooth highway?  All these will affect your hardware choices...

[johnsold]

You are in a tough spot. You need information and no one seems willing to give it to you.

Let's try to define some things.

1. Between the computer and the heater. The computer crunches numbers.  While the CPU heats up in the process, the computer does not connect to the heater. The power control device manipulates the power source (your 230 VAC or 24 VDC) so that a variable amount of power is supplied to the heater(s). The power control device might be a mechanical relay, a solid state relay, a transistor or thyristor, or even a switch which you operate when the termperature gets too high or low. The computer needs some means of communicating with the power control device.  These days computer communications is usually via USB or Ethernet. So you will need a device which speaks "computerese" via Ethernet or USB on one side and which speaks in the appropriate means to manage the power control device.

WE CANNOT TELL YOU OR YOUR BOSS what kind of device is required here because we do not have the requirements information. No oe else can tell you either. Anyone who tells you anything has made various guesses about your requirements and the recommendations cannot be any better than the quality of the guesses.

2. PID is not magic.  Many temperature control systems work fine with much simpler control algorithms.  Some cannot be controlled adequately with any PID system.  You have to know something about the behavior of your system before you can begin to select a control algorithm.

Repeat the paragraph above which says we cannot make recommendations without more information.

3. I am not trying to be hard on you. I also know that no one ever has all the information about a system before starting to design the controller. However, I have been doing this kind of project for 40 years.  To have any chance of success the first part of the project is always to get enough information.  Sometimes you need to make some measurements or to make some approximations and then compare the results to the expectations to see how close you might be.

For example you probably have at least an approximate target temperature, say 100 C.  You may not have specifications on accuracy, rate of change, overshoot and so on. You probably have an approximate size and shape of the plates and at least a preliminary idea of their material. From that you can do some thermal calculations to estimate how much power will be required to reach the target temperature over some time interval.  With that information you can evaluate whether the heaters on hand will be adequate and how much power will be required. Then you can start to chose the kinds of devices needed to sit between the computer and heater.  You might need to start with a simple on/off control and measure the dynamic behavior of the system to see what kind of control algorithm will be needed.

Lynn

[Top24]

Thanks for the anwser I realised somthing that are still missing and I din't realise their importance.

Right now I'm trying to create a simulation in PID in which I set a wanted temperature and I see graphically it's evolution if anyone knows any VI that could help me I'd apreciate.

I won't accept any anwser yet because i'll wait until I have more information to chose the hardware which is the topic of this post.

Thanks evaryone and if you have a VI that helps me I'll apreciate it.

[johnsold]

PID stands for Proportional - Integral - Derivative.  These all refer to the error signal which is the difference between the setpoint and the feedback from the output. So you can create your own VI to do PID.

The real problem with simulating a system like this is correclty modeling the behavior of the rest of the system. How fast does the heater change temperature when power is applied? What is the time lag between power applied and the change of the temperature sensor? What are the scaling factors for voltage to power to temperature throughout the system?

Lynn

[Top24]

I'm trying to do a kind of simulation that i define the speed of the temperature and I see it after PID a simple simulation