Operating Instructions for the PCB Multi-Trigger (MT-PCB3)
For reference, the various functions are indicated in Figure 1. Click on the image to open a larger version in a new tab or window. You may want to print the image for reference. Figure 2 shows a guide to the various functions. A printout of this guide is provided with the MT-PCB3 kit.
|Figure 1. Multi-Trigger PCB with functions indicated||Figure 2. Function guide|
It's best to have the Multi-Trigger turned off whenever connecting or disconnecting cables.
Using the delay unit and the external input
Lay the PCB on a non-conducting, static-free (as much as possible) surface. The thing to avoid is any surface that will discharge to the PCB or that will create shorts between the metallic contacts on the back of the board. Now do the following:
Set the Input Selector switch to MIC.
- Slide the delay range switch to 0.5 s.
Turn the timeout knob about a quarter of the way clockwise from its minimum position. A jeweler's screwdriver can be helpful in adjusting the pots.
- Turn the coarse delay (blue knob) all the way clockwise. The position of the fine delay doesn't matter at this stage.
- Connect a fresh 9-V battery to the battery clip and flip on the On-Off switch. The Power-on indicator LED should light.
- Press the test button. The Trigger LED should flash momentarily after a short delay. The amount of the delay is determined by the setting of the coarse delay pot. The amount of time that the LED remains lit is determined by the setting of the timeout pot. Try changing the coarse delay and timeout pots one at a time to see the effects that they have. Note that as long as the Trigger LED is lit, the unit cannot be triggered. This feature can be used to suppress multiple discharges.
- Turn the coarse delay as high as possible. Then flip the Delay Range selector to 0.05s. In this setting, all delays are divided by 10. When you push the test button, it will seem as if there is no delay. Actually, the delay is too short to discern just by watching the Trigger LED. These short delays are used for high-speed events that are initiated very quickly. Remember to return the Delay Range selector to the 0.5s setting when finished.
- When no sensor cables are connected to the unit, the test button will only function when the Input Selector is set to MIC. When a sensor cable is connected, the test button will work no matter what position the Input Selector is set to. Turn off the Multi-Trigger and insert the external input cable. Now turn the Multi-Trigger back on. Touch the bare red and black wires of the external input cable together. The Trigger LED should flash. A use for the external input cable is to connect it to a contact plate such as the one described here. The external input jack will also accept triggers such as the Crossed-Beam Photogate, the SK3 Sound Trigger, the Amplified Sound Trigger, and the light-activated trigger.
Using the photogate
- In order to use the Multi-Trigger with a photogate, first plug a photogate cable into the PG jack and set the input selector to PG. If you're using the photogate cable that has a separate emitter and detector, align them so that they face each other a few inches apart as shown to the right. (Click on the image for a larger version.) If you're using the interrrupter cable, no alignment is necessary.
- With the photogate plugged in and aligned and the Multi-Trigger turned on, the photogate alignment LED should be lit. If it isn't, try adjusting the white sensitivity pot one direction or the other. Setting the pot near the middle of its range should work. Note that if you change the separation of the infrared LED and PT, you may need to adjust the sensitivity to compensate.
- Run a finger between the infrared LED and PT. The alignment LED should go out momentarily. At the end of the delay interval that you've set, the triggering indicator LED should light momentarily.
Using the microphone
- In order to use the Multi-Trigger with the microphone, first plug the microphone cable into the MIC jack and set the input selector to MIC. Turn the red sensitivity knob about three-fourths of the way clockwise. (See the note about sensitivity adjustment below.)
- Clap your hands or snap your fingers. The triggering indicator LED should light after the set delay interval.
- If you need less sensitivity, turn the red knob counterclockwise.
More about the sensitivity adjustment: If the sensitivity is set too high, the circuit will hold the output closed continuously, thereby preventing further triggering. If you find that the trigger doesn't respond after turning up the sensitivity, dial it back counterclockwise until you can get a response.
About the outputs
The five outputs of the Multi-Trigger are of two different types, switch and pulse.
Switch output: A switch output provides the same function as a switch closure. This type of output is not a voltage source. Switch outputs are used to discharge most flash units and wireless devices.
Pulse output: A pulse output provides a voltage pulse (~7.5 V) that can be used to actuate an Opto-Switch. The Opto-Switch is used to actuate a camera shutter. A pulse output can also be used to discharge flash units whose synch circuits require a low-voltage pulse. The pulse outputs provide low currents and must not be used to directly actuate devices like solenoids. Doing so can damage the Multi-Trigger.
Protection from high-voltage synch circuits: Some older flash units have synch circuits that operate at a few hundred volts. Two of the outputs are protected from these high voltages so that they can be used with such flash units. These are the instant and delayed switch outputs. The sound trigger direct output and the two pulse outputs are not protected from high voltage.
Here's a summary of the relevant information about the five outputs.
|Output||Type||High-voltage protection||Delay||Timeout||Connects to|
|Sound trigger direct*||Switch||no||negligible||none||flash unit or wireless transmitter|
|Instant pulse||Pulse||no||negligible||none||Opto-Switch to control a camera shutter|
|Delayed pulse||Pulse||no||selectable up to ~0.5s||selectable up to ~ 1s||Opto-Switch to control a camera shutter|
|Instant switch||Switch||yes||negligible||none||flash unit or wireless transmitter|
|Delayed switch||Switch||yes||selectable up to ~0.5s||selectable up to ~ 1s||flash unit or wireless transmitter|
*The sound trigger direct output bypasses the delay unit. This output would be used to obtain maximum sensitivity of the sound trigger. Note that this output should not be used with flash units having high-voltage synch circuits. For such flash units, use the instant switch output.
Triggering a flash unit or wireless transmitter
Caution: If your flash unit has a high-voltage synch circuit, don't connect it to the Sound trigger direct output. You may, however, connect such flash units to the Instant switch and Delayed switch outputs.
Flash units designed for use with cameras have a synch circuit that works by a simple short of its external contacts. Connect such flash units to the switch outputs. (See the cautionary note above.) Some studio units require a low-voltage pulse to trigger. Connect these flash units to pulse outputs.
Wireless transmitters are typically triggered in the same way as camera flash units with a simple switch closure. Connect wireless transmitters to the switch outputs.
Triggering a Camera via an Opto-Switch
Caution: Don't connect a camera directly to a pulse output of the Multi-Trigger. This would send a low-voltage pulse through the camera's shutter circuit.
An Opto-Switch must be connected to a pulse output in order to actuate a camera shutter. Make these connections:
- Connect either pulse output to the TRIG jack of the Opto-Switch.
- Connect the CAM jack of the Opto-Switch to the camera.
Once the connections are made, the Opto-Switch may be used according to instructions provided with it.