mwandel@bnr-rsc.UUCP (Markus Wandel) (06/17/91)
I want to try some experiments which would require one or more photo flashes to be fired under control of a digital logic circuit. As far as I know, the sync contacts of the typical photo flash present a DC potential anywhere from a few volts to a few hundred volts which when shorted out by the camera, fires the flash. There must be a fairly standard method/device used to accomplish this other than a mechanical contact. Before I delve into the databooks to try to figure this out myself, I thought I'd just ask here. Tips, hints, schematics, part numbers from Radio Shack or other common component supplier, would all be appreciated. I seem to recall a schematic for a "sound trigger" a while ago but can't find a copy. Markus Wandel
tarrall@Colorado.EDU (Counselor Neon) (06/17/91)
mwandel@bnr-rsc.UUCP (Markus Wandel) writes: [parts deleted...] >Tips, hints, schematics, part numbers from Radio Shack or other common >component supplier, would all be appreciated. I seem to recall a schematic >for a "sound trigger" a while ago but can't find a copy. Clap on... (clap clap) *flash* Clap off...(clap clap) *flash* Clap on, clap off, the Clapper... (hehehehehe...) Just wait for the new Minolta 8xi... >Markus Wandel -Neon.-
mcovingt@athena.cs.uga.edu (Michael A. Covington) (06/17/91)
Try an SCR rated at 400 volts. It will "reset" itself automatically after triggering because the voltage across the flash connector disappears when the flash fires, then comes back a moment later. -- ------------------------------------------------------- Michael A. Covington | Artificial Intelligence Programs The University of Georgia | Athens, GA 30602 U.S.A. -------------------------------------------------------
menzie@plains.NoDak.edu (Mark Menzie) (06/17/91)
One common method to sync flashes uses a light sensative trigger. When a flash fires it trips a photocell detecetor which signals another flash to fire. You could setup several flashes to fire this way and all would go off just a few milleseconds after the first..... mark menzie menzie@plains
horn@cbnewsi.cb.att.com (david.n.horn) (06/28/91)
Markus Wandel asks: >I want to try some experiments which would require one or more photo flashes >to be fired under control of a digital logic circuit. I have successfully used several types of Silicon Controlled Rectifier (SCR) or Triac to fire electronic flashes. Radio Shack used to sell a optically- triggered SCR that made a very sensitive "slave" - just by itself, but they have not been selling it for several years. Another device that makes a good, safe, all-purpose interface to a flash is a opto-isolated TRIAC/Driver combination, such as the Motorola MOC3009 - MOC3021 family. I have recently bought one of these from Radia Shack, but I do not have the part number. It is in a little white 6-pin DIP package. Two pins are the photo-sensitive Triac. Connect them to the flash PC socket. The other two pins are an LED. Pass enough forward current through the LED and the light from the LED will turn on the Triac and fire the flash. The LED and the Triac are seperated by clear plastic, thus providing several Kilovolts worth of insulation between the two sides for safety. The MOC3009 requires 30ma though the LED, the MOC3010 15ma, the MOC3011 10ma. You can drive the LED from a TTL device or anything else, but be careful to limit the current or you could blow the LED. I have also messed around building my own flashes. But let me warn anyone delving into the inside of an electronic flash - they are deadly dangerous! The capacitor holds a lethal charge at 200 - 500 volts, even hours after being switched off. Dave Horn