by Scott Parvin » Feb 20, 2008 11:13 am
Another update:
I was doing some research on David Gibson's design and found this in an article:
Connecting the Flashgun
The unit has two terminals, and these
should be connected to your flashgun
through whatever connector you have chosen
to use. The slave unit needs to be configured
by setting a movable shorting-link on the
circuit board. Push the programming link
onto one pair of the three programming pins.
Position 1 is towards the terminal end of
board; position 2 is towards the battery end
of board. Position 1 works with most flashguns,
and flashbulbs. Position 2 works with
all flashguns, but not with flashbulbs.
The problem arises because of the
differences in the trigger circuit in flashguns
from different manufacturers. Typically, it is
certain Vivitar guns that require the link to be
in position 2 – for most guns it should not
matter what the setting is.
Use with Vivitar Flashguns
A common problem with slave units is
that they will not work with some models of
flashgun, in particular (but not limited to)
Vivitar guns. These use a different design of
trigger circuit, which results in a larger
current flowing when the contacts are closed
(or in this case, when the triac fires). The
current causes the triac to latch on
permanently. (Technically, this is due to the
‘holding current’ of the triac. I have used an
opto-triac for convenience, but its holding
current is only 100μA so the problem can
easily manifest itself on a variety of flashguns).
C6 with its bleed resistor R17 are
included to get around this problem. A word
of warning: you can use this ‘Vivitar’
connection to fire ‘ordinary’ guns too, but the
capacitor must be rated at 400V or more.
Maybe this applies, maybe it doesn't. I'm not sure if the Firefly has the programming link like David Gibson design...I'll have to open mine up tonight and take a look. I'm in the process of homebrewing a trigger, so I hope to get this all straightened out soon.
Scott A. Parvin
NSS 29279 RL, FE
Disclaimer -- Views expressed are mine and do not reflect the opinion of the NSS or Board of Governors.
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