using an input signal to start and stop Vis

[scurley]

IO have a Vi that needs to be started and stopped by a signal coming from a sensor on an automated production line. the problem is that the Vi i have created to capture and compare images from a webcam mounted on a robotic arm that is being used to tighten screws into a part needs to be started and stopped by a human using the Vis "run" buttons at the top left of the Vis front panel. how do I use an input signal from the sensor (+5 V for 10 ms) to statrt and stop the Vi? The Vi can't be allowed to run when there are no parts for the robotic arm to work on as it would consume electricity that costs money.

[jyang72211]

I think this maybe what you are looking for.

http://ni.lithium.com/t5/LabVIEW/Can-I-use-an-Event-Structure-to-process-an-input-signal-from-a/td-p...

[scurley]

The system would not be fully automated if the production line, associated computers, the LabVIEW software running on the computers and the Vi's being used by the various stages in the production line need to be powered up by a human.

The idea is that humans are removed from the ENTIRE production process, in effect I'm trying to create a completely automated business. 

The production process would be set in motion when an order (having been paid for via PayPal (as the payment confirmation would be the trigger for the production line to start up and manufacture the required number of products for to satisfy the order)) comes in from the website.

The Fixing station is just one stage in the production line process and I thought it would be a good place to start the automation of the business.

The problem is that a human is required to start the Vi. I need to remove the need for any humans to start the Vi. The Vi needs to be started running automatically.

Your suggestion seems to require that the Vi is already running and is sitting in a while loop or something until it receives the digital input signal. 

I think what I want to to is too much for LabVIEW to deliver. I'm also looking into using Windows Presentation Forms (WPF) with C# as the code behind to give the GUI functionality.

The GUI is a necessary requirement in order for me to be able to sporadically monitor the system, should I feel the need to do so, without having a need to do so.

Have I understood that the Event Structure can only take effect if the Vi is running. I need a way to stop and start the Vi.

I think this conversation has taught me that I'll need to use either a single LabVIEW Vi for the entire business inluding the website and administration side of things or just use a WPF.

Thanks for trying to help though.

As for the robot arm image capture problem the Vi would need to be set running by another program (the WPF) so I might as well use that program to capture the image and process it, I just thought I could take advantage of LabVIEWs IMAQ functions to do the job.  

I understand that I can use the digital input to start the image capture process but I needed a way to use the digital input to start the Vi running.

[johnsold · Accepted solution]

No program in any language can be started by an external signal.  Some software needs to be running to detect the signal.  Whether that software is an embedded program running on a microcontroller, or a multi-processor super computer it still works the same way.  The power required by the computers is likely small compared to the power consumed by the robots and other manufacturing processes.

As you described your system, you will need a computer running all the time waiting for something to happen on the website indicating that a paypal transaction has taken place.  What is different about having a computer running LV with a VI in an Idle state?

If your process is to be economical, you better hope to have enough orders that you are not turning off and on the entire sytem very often.  The cost of automating everything wold not be covered by the sproradic revenues.

It is certainly feasible to have a master computer which controls power to portions of the system which are not needed continuously.  Use PLCs to control solid state relays or contactors to switch power to various subsystems.  Make sure that enough time is allowed for the systems to power up and initialize before starting production.

I would concentrate first on getting the automation working from an active but idle condition before trying to go to complete power down and up control.  I think you will find that the power up process will require sitting in an idle state for some parts of the system while other parts are being initialized, so you need to do the Idle state anyway.

Lynn