Is it possible to trigger a webcam?

[Darien]

I am trying to make a breakdown experiment where a high voltage RF pulse is sent of a set of electrodes in front of a viewport. My pulse is typically about 100mS. I want a cheap/simple way to see if I have an arc (to correlate that with my other signals). I think a webcam will have as much resolution as I need. Does anybody knows if I can trigger the webcam using labview (or some other program). I can use a second trigger before the power pulse as needed, but I don't know if those libraries mentioned in other posts allow the control of the webcam to capture images using a trigger event, and/or how many FPS can I obtain from a webcam.

Basically, I am thinking of sending a pulse, letting the webcam to capture frames for say 0.5-1 second. And display the images captured, so I can save or whatever. I am not interested in analysis. The contrast should be good, light (arc) and darkness (no arc). Could anybody recomend a camera that works. I want something as simple to setup as possible, I don't know if there is a preferable model or something. For example, I was thinking of the Logitech QuickCam Pro 4000, or the Phillips Vesta PCVC 680K which seems to be the favorite of astrophotographers (good sensitivity in low light conditions).

Thank you very much for any help.

Darien

[Conseils]

What immediately comes to mind with a web cam is that at high resolution the frame rate is liklely to be 15 frames per second, that means that you could typically expect about two or three frames of full resolution data. I have had higher but it's unstable more often than not and easily stopped by any other activity on the USB bus.

As far as triggering is concerned I guess you just aquire data in a circular buffer and have an external trigger start and if necessary stop the aquisition into the circular buffer.

If you use a video camera you should get better contrast range, higher dynamic range, significanlty better focul distances and shutter speed control. Also if you use firewire you will get all the frames. You could also record the data without the computer as a high voltage spike of the type you are describing is likely to stop or ruin just about everything electronic not within a faraday cage, this could be challenging when you are tyring to put a hole in the cage to poke a camera through!

I guess you have some specially coated glass for that?

[unclebump]

I downloaded the quickcam software from logitech. I didn't see any activex items added by the camera software install. You may be stuck with trying to access the camera using dll's. Is there any developer software for the cameras??

[km76107]

Yes.  There are several software that you can use for webcam.  I developed an application where i was reading off a wireless webcam using LabView.  I used a D-Link webcamera.  I Vision, Warwick technologies and Intel PC provide some free downloads for webcams

Let me know if you need more information. 

[AnalogKid2DigitalMan]

If you just need to sense an arc (light present) versus no arc (dark) why not just use a photodiode with an amplifier and a comparator? Granted, some circuit wiring required, but this approach will give you a simple digital ON/OFF signal with response times of microseconds. Thus much cheaper, faster, and no post image analysis required. IMHO, camera approach for this application is akin to swatting a fly with a sledgehammer.

Slower devices that also could be used are CDS photocells or solar cells.