Handbook of High Speed Photography - IET Labs, Inc.

5.3.2 OTHER SIGNAL PROCESSING DEVICES. If only one or two
simple processes are needed to modify the signal for use with a par
ticular stroboscope, it will probably be most economical to build a
device suited to the particular situation faced by the photographer.
For example, only a contact closure may be available to trigger the
1531 Strobotac which requires a contact-opening signal with zero delay.
A simple inverting circuit will be required, such as that diagrammed in
Figure 5-10. The necessary parts can be purchased for less than $2.00,
and only a few minutes are required to assemble them. Contacts in
camera shutters equipped for X synchronization normally operate satis
factorily with this circuit, but some difficulty may be experienced if
the contacts bounce when closing. A small capacitor (around 0.01
microfarad) connected externally across the contact terminals usually
solves this problem.
TO SHUTTER OR
SWITCH CONTACTS
1
TO STROBOTAC
INPUT JACK
B - 12-volt (or greater) battery
Ra» Rb ~ 1-megohm, J4-watt carbon resistors
S - SPST ON-OFF switch
Cs - Optional capacitor to prevent
multiple triggering from contact
bounce. Start with about 0.01 £iF
(100 V, dc) and increase capaci
tance until only one flash is trig
gered from each contact closure.
Cp - 0.01 /iF, 100-voIt capacitor
NOTE:
Set RPM dial fully clockwise.
Figure 5-10. Circuit for triggering the Strobotac by a contact
closure with minimum time delay.
The internal delay characteristics of the General Radio Strobo
tac electronic stroboscopes can be used to introduce a variable delay
between a negative or contact closure input signal and the flash. This
method of obtaining a time delay, however, is not time stable and may
introduce appreciable time jitter ; for this reason, use of the Flash De
lay is preferred. The delay varies from approximately 20 milliseconds
with the RPM dial fully counterclockwise to 300 milliseconds with the
dial at a point approximately 90° away from fully clockwise. As the
RPM dial is swept past this point, the flash will fire without being ex
ternally triggered. At the full clockwise end of the dial, zero delay
will occur. These flash-delay characteristics are summarized in Figure
5-11.
It is usually necessary to provide phase adjustment within the
picture-taking system, so that the subject is in the proper position
when the lamp is fired. The easiest way to do this is to use a device
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