Output Stage

Figure 3. Functional block diagram of the Flash Delay.

Figure 4. The action of cam followers can be easily examined with the Strobotac-Flash Delay combination. These photographs show the bounce of a cam follower at high speeds. The cam is rotating counterclockwise.

low-power devices such as relays, mechanical choppers, etc. The pickoff, with a time constant of approximately 200 ┬┐isec, can be used with equipment rotating at speeds in the hundreds of thousands of rpm.

The Type 1531-P2 Flash Delay makes possible single-flash photographs of rotating equipment at any desired position in its cycle. The single flash of the Strobotac is synchronized both with the time the camera shutter is open and with the desired position of the rotating object.

Description

The Type 1531-P2 Flash Delay was designed primarily for use with the Type 1536-A Photoelectric Pickoff.1 It can be triggered, however, by any transducer that will generate a positive electrical pulse of at least 0.3 volt. The block diagram of Figure 3 shows that the flash delay consists of a preamplifier, a Schmitt-circuit pulse shaper, a time-delay generator (consisting of a flip-flop, a unijunction transistor and rc network), and an output stage. Each trigger pulse from the Schmitt circuit starts a delay cycle. When the voltage across a capacitor in the rc circuit reaches approximately 9 volts (one-half the 18-volt charging voltage), the unijunction transistor fires, discharging the

capacitor, resetting the delay flip-flop, and sending a pulse to the output amplifier.

There are three delay ranges available. Range 1 allows an adjustment over 300 degrees for rotational speeds of 0000

Figure 5. A typical application in the textile field: observing tape and filling-carrier behavior of a Draper DSL shuttleless loom. Speed of the filling carrier is 274 picks per minute. The Flash Delay makes it possible to observe the filling-carrier at any particular point on its path. Synchronism with loom is accomplished with the Type 1536-A Photoelectric Pickoff located near a rim connected to the main power shaft and shown at the bottom of the photograph.

Figure 5. A typical application in the textile field: observing tape and filling-carrier behavior of a Draper DSL shuttleless loom. Speed of the filling carrier is 274 picks per minute. The Flash Delay makes it possible to observe the filling-carrier at any particular point on its path. Synchronism with loom is accomplished with the Type 1536-A Photoelectric Pickoff located near a rim connected to the main power shaft and shown at the bottom of the photograph.

Figure 6. Study of thread behavior in high-speed sewing machine. Machine speed was 5000 stitches per minute; hook speed was 10,000 rpm. Photograph at feft shows setup using LinhofF 4x5 with Polaroid film, Strobotac with attached Flash Delay, and sewing machine (the base of which is cut away to expose the parts underneath). Center and right photographs show the bobbin and hook action on thread at a specific phase selected by means of the Flash Delay. Photographs courtesy of The Singer Company.

Figure 6. Study of thread behavior in high-speed sewing machine. Machine speed was 5000 stitches per minute; hook speed was 10,000 rpm. Photograph at feft shows setup using LinhofF 4x5 with Polaroid film, Strobotac with attached Flash Delay, and sewing machine (the base of which is cut away to expose the parts underneath). Center and right photographs show the bobbin and hook action on thread at a specific phase selected by means of the Flash Delay. Photographs courtesy of The Singer Company.

rpm or higher; range 2 provides the 360-degree adjustment for speeds between 600 rpm and 6000 rpm; range 3 is used for speeds below 600 rpm and for special applications in which a delay as long as 0.8 second is required.

For single-flash photography, the output pulse from the delay circuit goes to a flip-flop gate circuit instead of directly to the output stage. If the x contacts of a camera shutter are connected to a jack on the flash delay, their closure will make the gate circuit conduct, and the next synchronized, delayed pulse will pass to the output stage. After this one pulse passes, the flip-flop gate will reset and again become nonconducting. The flash delay, therefore, allows the first synchronized pulse occurring after the camera shutter opens (x-contact closure) to trigger the stroboscope. Synchronism is thus obtained with both the shutter opening and the desired position of the rotating object. It is necessary to set the shutter speed so that the

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