High-Performance Slave Unit SLV023

Other pages in this archive: Slave: Questions | Slave: troubleshooting | slave2005-1a.pdf | SLV023_kitcheck.pdf | slv023-BOM-1v1-A.pdf

i) Features

• Very high sensitivity
  The line-of-sight triggering range is around 1200m with a gun of GN 30m @ 100ASA. This high sensitivity allows the slave to "see" around corners in dark passages.

• Infrared sensitive for use with "dark" flashguns
  It is useful to trigger a slave from a flashgun mounted on the camera, but you might not want the foreground to be illuminated. The visible light can be blocked using an infrared filter. Flashguns generate a significant amount of infrared light. This is detected by the slave and triggers the main flash.

• Usable underwater
  The photodiode is sensitive to visible light as well as infrared. For underwater use, where infrared is attenuated, the unit works when other commercial units (which are only sensitive to infrared) will fail. (Note: the Firefly unit is only infrared-sensitive, so its performance underwater is limited)

• Not sensitive to caplamp beams
  The slave is triggered by the short, sharp, bright pulse from an electronic flashgun. It should not respond when a caplamp is shone at it.

• Not adversely affected by ambient light
  Cavers will usually be operating the slave unit in the dark, so the question of ambient light does not arise. However, if you want to operate it in conditions where there is some light you need to know how its performance is affected. The response has been tailored to work in ambient light as a fill-in flash. It will trigger when a near-instantaneous pulse of light exceeds the general light level by around 3½%. In terms of photographic "stops" this is about 1/20 stop.

• Triggered by, and will fire flashbulbs
  The unit is designed to be triggered by the sharp pulse from an electronic flashgun, and to ignore the much slower changes in light level caused by a wavering caplamp beam. Flashbulbs come somewhere in between. As it stands, the unit can usually be triggered by a flashbulb. The revised slave unit, now available has been enhanced to allow it to fire flashbulbs more reliably than the previous unit. A combined slave and bulb firer is also available.

• Compact design
  The unit will fit inside a translucent 35mm film container. It could, perhaps, be placed inside the casing of a flashgun, and operated from the flashgun's own batteries. The size of the circuit board in the current version is 46mm x 23mm, but it can be trimmed to a smaller size if the on-board battery is not required..

• Low current consumption: life of 4 years or 10,000 flashes
  One 3.6V lithium cell (size ½AA) provides enough energy for 10,000 flashes, and will run the unit for 4 years. Since this is comparable with the shelf-life of the batteries an on/off switch is not required. This, in turn, means that a simpler connector (which doesnt have to double as a switch) can be used. Alternatively, the built-in opto-isolation means that the unit can be run from the flashgun batteries themselves.

ii) Setting-up Procedure

• Fit a battery
  Fit a 3.6V lithium cell (size ½AA; 25mm in length x 15mm diameter), making sure that you observe the polarity. Lithium cells are available from photographic and computer stores; the battery is used for memory backup in some computers. A typical part is the Sonnenschein SL350/S, or the Tadiran SL750/S. This is a 3.6V, 1.1Ah Lithium Thionyl Chloride cell, available, in the UK, from Farnell Electronic Components, stock number 118-7264. alternatively, Maplin Electronics stock a Maxell battery, ER3S_TC, stock code QE49D. Note: those stock codes may be replaced by more recent ones; you may have to do a web search.

• Wire a connector
  The slave unit is not supplied with a 'hot-shoe' connector, but a phono (RCA) plug and lead. This is connected to the circuit board via screw terminals, so you can wire your own connector and lead if you wish.

• Select the link position
  Push the programming link onto one pair of the three programming pins. Referring to the photo, position 1 (as shown) is to the right (terminal end of board), and position 2 is to the left (battery end of board). Position 1 works with most flashguns, and flashbulbs. Position 2 works with all flashguns, but not with flashbulbs.