Controlling temperature and pressure

[Moses2]

Hi,
I'm looking for some input how to control the pressure and temperature of a laminator.
The pressure is created by air (6 bar) and I use a valve which can be controlled by a 4-20mA current interface. For the temperature a Pt-100 sensor is available. I want to control the energy of the heating elements by a PWM (main power).
All the data acquisition and control functions should run on a standard PC... That's the plan.

I would appreciate if somebody could recommend some components or resources?

Thanks
Moe

 

[KeepItSimpleStupid]

PWM isn't used for main power. What is your mains voltage and the wattage of the heater? Phase angle firing is used instead. The PC cant do it directly because of timing issues. You can buy a device that will take a 4-20 mA signal and output a voltage proportional to Vrms ^2.


PWM works on DC power sources.

An auto-tuning PID temperature controller with some sort of interface (serial or analog) might be your best choice.

PT100 isnt a bad choice for a sensor.

Not sure how a 4-20 mA valve controls pressure. What I initially think of would be a diaphram or air cylinder controlled by a vent solenoid and in solenoid that can be pulsed with a way to measure pressure. I'm not saying it's the only way.

PID can be done in software.

LabView is a popular DAQ package. A very strange data-flow language. The PID software is still probably an extra add-on.

 

[tunedwolf]

All of the flatbed laminators that I have worked on use the compressed air to raise and lower a pressure roller constructed of steel with a smooth silicone outer layer. There is no actual pressure control, besides an inline standard water trap/ filter/ regulator being fitted. The most common temperature control that I have seen on them uses IR to monitor the silicone roller surface and simply switches on/ off a 12V relay with a little hysterisis, that in turn, switches mains going to a linear heating element held concentrically inside the steel roller. The controls really couldn't be any simpler. Is this a retro fit, or are you looking to design a completely new way of doing things?

 

[large_ghostman]

I suppose if one of the rollers is moving you could measure the current, the more pressure the more current needed to turn the roller? But someone mentioned a flatbed laminator and I havnt got a clue how those work sorry

 

[Steven_L]

I don't have experience with laminators but if you want to acquire some temperature and control a PWM you should check https://www.lucid-control.com

Agian, I don't know if this will work with a lamination process (timing, accuracy, reliability, etc.), but they are able to handle the required signals.

 

[Pommie]

Assuming your heating element has thermal mass then you can use burst control. Turn on at a zero crossing point and turn off 1 to 100 crossings later for 1 second burst heating.

Mike.

 

[large_ghostman]

rereading the post I am sue what I am thinking about is nothing like the machine the Op is using

 

[dr pepper]

You could use pwm, lookup arduino, there is a pid library available for the arduino, this would be ideal for temp control, the library comes with a example to control a relay fo thermal control, a laminator has a high time constant so slow on/off ought to work.
Theres probably a library for current loop control to drive your i to p valve.

Edit: reread your post you say functions are to run on a pc, well you could still use the'duino for i/o and do the rest on te pc, the 'duino has usb to rs232 on board.