Re: Coil photograpy idea

To: tesla-at-pupman-dot-com
Subject: Re: Coil photograpy idea
From: Jim Lux <jimlux-at-jpl.nasa.gov> (by way of Terry Fritz <twf-at-verinet-dot-com>)
Date: Sat, 06 Mar 1999 09:04:13 -0700
Approved: twf-at-verinet-dot-com

Tesla List wrote:
> 
> Original Poster: wwl-at-netcomuk.co.uk (Mike Harrison)
> 
> I just had an idea about a new way to get potentially good , or at
> least diffrent. pictures of a coil firing.
> I have a CCTV camera which has a fast shutter mode, and also a genlock
> (external sync) input. If I generate a dummy frame sync for it to lock
> onto, derived from the mains frequency via an adjustable phase delay,
> it ought to be possible to take fairly fast (down to about 1mSec I
> think) 'snapshots' at fairly precise, repeatable intervals relative to
> the mains cycle, and therefore observe different stages in the spark
> formation, as well as observing the effects of such things as spark
> gap firing jitter etc. The result could either be recorded on video
> tape for frame-by frame analysis, or better, (unless a VCR with very
> good stillframe is used), digitised to hard disk.
> (I also have a very good zoom lens so I can keep it well away from the
> coil :-)
> 
> Has anyone tried anything like this before ?
> 
> I've just bought a PCI video capture card, but probably won't have
> time to play with it for a couple of weeks :-(
> but I definately will try this & will post any news.

This works quite well.. I've done it for other similar applications
where I needed to synchronise a camera to a line synced flash (in my
case, I was synchronizing opposite the flash).

Elantec has a couple of very nice IC's to do the sync separation and
regeneration. You'll have to deal with the issues of fields vs frames.
What sort of sync input does the camera want? "black burst", NTSC video,
or just a TTL pulse?

You might want to email me off-list and I can give you a whole lot of
info on this area...