Frequently Asked Questions
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- Can I use the crossed-beam photogate with the Multi-Trigger?
The project box kits (AstroSplash, Multi-Trigger 3, Crossed-beam photogate, and Light Sensor, all have outputs to trigger cameras. For our breadboard circuits, one option is the Camera Opto-Switch. This provides the best isolation between your camera and the circuit electronics. Another option is a DIY cable. See this link.
Definitely. Most wireless controllers are actuated by a simple short circuit. That's the output that HiViz.com circuits provide.
Yes, this is possible with some flash units. One method is to connect the flash units in parallel across the output. We've used this method with as many as 10 Vivitar 283s. This works best if using all the same make/model of flash. It's not recommended if using different flash units, and it's possible that it won't work for some models. And here's something to be especially careful of. There are two different version of Vivitar 283s; the older version has ~300 V across the flash terminals. Connect one of these in parallel with a neter version that has ~10 V and you could have problems.
Another method which gets around the possibilty of one flash's trigger circuit affecting anothers is to use wireless transmitters and receivers, such as PocketWizards. Connect a transmitter to the output of the trigger circuit. Then put receivers on the flashes that you want to discharge simultaneously.
A disadvantage of wireless transmitters is that they tend to have a lag of a millisecond more. That may not sound like much, but it makes a big difference for events suchs as balloon bursts. In that case, optical slaves are superior. The Light Sensor makes a nice slave.
With critical alignment and sensitivity adjustment, 12 inches (30 cm) is possible. For larger distances, a red laser pointer can be used in place of the infrared LED. The detector is sensitive to red light as well as infrared. When using a laser, you may need to place a pinhole aperture in front of the laser so that the beam on the emitter isn't too intense. (This tip comes from Roy Marshall.) Note also that a red spot may appear on the subject so try to arrange things so that the red spot will be on the opposite side of the subject as the camera. Alternatively, you might be able to edit the red spot out of the photograph.
One problem with many laser pointers is that the pushbutton is momentary. If you use such a pointer, you need to clamp or tape the button down. Nowadays, it should be easy to find laser flashlights with buttons that don't have to be held down.
If your flash unit doesn't have a cord, it must have connections on the foot for triggering it. You can get an adapter shoe that fits on the flash foot and has an output PC cord. Here are two sources: 1) https://www.adorama.com/fapchsa.html, 2) https://www.bhphotovideo.com/c/product/764588-REG/Nisha_HTS_T_Hot_Shoe_Tripod_Mount.html.
First put the SB-600 in manual mode. Then you'll need a way to attach the SB-600 to the trigger circuit output. See the following link for a way to do that.
Thanks to Tom Denham for the information above.
The variable-width photogate is more flexible than the interrupter style, because the emitter and detector can be positioned independently of each other. Objects of various sizes can pass through the photogate. The interrupter style uses the component shown to the right. The emitter and detector are fixed in position in a plastic housing. This is convenient for triggering on drops but is limited to objects that can pass through the gate. You can use either type of photogate with the same base trigger circuit.
When connections are made according to this chart, the output is a short circuit. This can be used to trigger most flash units. When connections are made according to this chart, there is a voltage output a little under 9 V. This can be used to actuate an optoisolator (such as the Opto-Switch) or a flash unit that requires a low-voltage trigger pulse.
Cameras should not be connected directly to the low-voltage outputs.
The circuitry for the crossed beam photogate is different from that in the Multi-Trigger. So you couldn't, for example, connect the PVC frame to the photogate input of the Multi-Trigger. You can, however, use the delay unit of the Multi-Trigger with the crossed-beam photogate. To do this, you would connect the SCR output of the crossed-beam photogate circuit to the external input of the Multi-Trigger.