RE: RF Interface

Michael,

I do photo shoots at events where there are other photographers, syncing to a flash causes mine to fire and then the recharge cycle begins, if I use my system during the recharge, I waste film. So I either hard cable, or encode. I'd prefer to encode. I don't do this often or for enough money to justify the commercial units, I thought if there was a way to use the PIC and some type of Xmtter/Rcvr pair.

Doug

----- Original Message -----

From: Michael Rigby-Jones

To: PICLIST@MITVMA.MIT.EDU

Sent: Thursday, December 09, 1999 12:21 PM

Subject: Re: RF Interface

I've read with interest the messages about RF and IR remote interfacing projects, I'd like to put together a remote interface that triggers a camera strobe based on trigger from the camera itself. Commercial versions of this in RF area are in the several hundred dollar range. I've looked at the Ming series and the decode time I believe would not lend itself to syncing with a camera. Most camera's (35mm) sync at around the 1/60th of second speed. I have shuttered lenses that sync at upto 1/500th of a second. I have a 16F84 that I use with a direct connection to trigger via a cable a second strobe. I'd like to rid myself of the cables.

Long winded I see, my question is, are there available RF or IR modules that would decode in time to sync at 1/500th? I don't want to use unencoded modules as false trigger would be fairly expensive waste of film.

Surely false triggering wouldn't be such a problem, a slave flash firing when it shouldn't wouldn't waste film, I guess you are more concerned about it NOT triggering.

I built a simple slave flash many years back that just used a phototransistor to detect the primary flash and fire a triac that was connected to a slave flash. A high pass filter ensured that the device only responded to very fast changes in light and false triggering was never a problem. Could you not use something like this? To achieve a similar latency with an encoded bit sequence is going to need a pretty high bit rate. There won't be time to do a full send/acknowlege unless you are running at some obscene bit rate, so this setup will be inherently more unreliable than a cable or simple optical setup.

Regards

Mike Rigby-Jones