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Assembly and Operating Instructions for Kits


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Assembly Instructions for the Multi-Trigger Enclosure (MTE)


Assembly instructions for other kits


If you are an MTE early adopter and purchased your MTE kit prior to January 11, 2011, see the instructions here.




What you need

Parts guide (opens in new window)

Drilling holes in the project box lid

Adding the components to the project box lid

Wiring the box lid

Soldering some of the connections

Preparing the cables

Preparing the breadboard

Adding the battery holder

Soldering jumper wires to the box lid components

Step-by-step testing

Closing up the box and final testing

Reported issues

Operating Manual for the MTE

Possible modifications


What you need


These instructions show how to build a project box enclosure for a Multi-Trigger. Here's what you need to get started:

  1. Multi-Trigger Kit with Breadboard
  2. Multi-Trigger Enclosure Kit
  3. Adapter for connecting the output cable to your flash. See either PC cord adapter or Flash-to-PC adapter.
  4. This is optional: If you want to trigger a camera shutter, you'll also need a Camera Opto-Switch Kit.
  5. Also optional: If you want to power the circuit with an AC/DC adapter, you'll need something like this. This isn't a requirement, as you can always use a 9-V battery.

We highly recommend prior experience in circuit building and project box construction. If you need to troubleshoot, you're pretty much on your own to use these instructions, since troubleshooting project box wiring isn't something that lends itself to email. As a last resort, you could send a non-functioning unit to us for testing and repair. If you want to do that, contact us first so that we can give you an estimate of the repair cost.


Here are the tools you'll need:

  1. Drill motor and bits to drill holes in the project box lid. Bit sizes are 3/32", 1/8", 1/4", 9/32", and 5/16". (For metric equivalents in millimeters, multiply by 25.4.) You can substitute a 1/8" bit for the 3/32" one. You can get by without the 9/32" bit by drilling a 1/4" hole and filing it larger.
  2. Hammer, punch (or nail), small round file
  3. 15-30 W soldering iron and solder
  4. Wire stripper, needle-nose pliers, diagonal cutter (see images below)
  5. Wrenches or sockets to tighten components onto the project box
  6. Lighter or matches, hot glue gun and glue sticks

    Wire cutters and stripper

    Small diagonal cutter

    Needle-nose pliers


    In case you haven't done much soldering, here are some tips.

      Soldering Tips

      • Solder in a well-lit, well-ventilated, open area. Avoid contact with all metal surfaces on the iron.

      • Keep the tip of the soldering iron clean by wiping it against a wet sponge or towel before and after each use. A clean tip should look shiny and silvery; any yellow or black material on the tip will get into the solder and may weaken your solder joint.

      • Once the tip of your soldering iron is clean, touch a bit of solder to the tip just before use. This is called tinning, and helps the solder run more evenly.

      • Heat the connection to be soldered by holding the soldering iron to it, until solder applied at the junction between the two melts and flows freely. This ensures the connection and the solder are both hot enough to yield a good solder joint. This should take no more than 10-15 seconds. After the connection is heated, try to get solder along the entire length of the connection by briskly moving the solder and iron along.

      • Avoid touching only the solder to the connection, and then the soldering iron to the solder to melt it onto the connection. The connection will be cooler than the melted solder and won’t form a good solder joint.

      • Let new solder joints cool for several seconds before examining them. There should be solder all the way around the connection, forming a rigid joint. When done, unplug your soldering iron and let it cool.

Important: Before attempting to build the enclosure, build the Multi-Trigger on a breadboard first according to these instructions. A working Multi-Trigger is a prerequisite to integrating the circuit with the enclosure.


Parts guide (opens in new window)


Drilling holes in the project box lid

  1. The template is sized to fit snugly within the underside of the project box lid (that is, on the interior side of the box). Position the template inside the lid and then use a nail or punch to mark the positions of the centers of the holes to be drilled.

  2. Remove the template and drill the holes. We recommend drilling small pilot holes first, for example, 3/32" or 1/8". The plastic has a tendency to grab the bit, so hold the plastic securely. We've found that a spade bit works best for drilling the quarter-inch holes. If you don't have a 9/32" bit, you can use 1/4" and then file the hole to a larger diameter for the pushbutton.

  3. Use a round file to clean up any burrs around the holes.

Adding the components to the project box lid


The photos below show the top and underside views of the box lid with all the components mounted.

  1. The LED mounts have two parts, which we will call the collar and the ring. (See the Parts Guide above.) The collar is first slipped down into a hole on the project box and snapped into place. Then the LED is pushed up into the collar from below and snapped into place. The ring is then pushed over the collar from below to hold the assembly tightly.

  2. Remove the nut from each 3.5mm jack, insert the jack through the box lid from below, and screw the nut back on. Needle-nose pliers can be helpful in tightening the small, round nuts.

  3. Remove the nut from the AC/DC input jack, insert the jack through the box lid from below, and screw the nut back on. You can use a wrench on this nut.

  4. Remove the nut and lock washer from the pushbutton, insert the pushbutton through the box lid from below, slip on the washer and screw the nut back on.

  5. For an RCA jack, remove the nut, metal tab, and washer (if present), from the jack, insert the jack through the box lid from above, slip the metal tab and washer on under the box lid, and screw the nut on. While you can use a wrench to tighten these, keeping the jack from turning while tightening requires a strong grip on the jack.
  6. The switches have a retaining ring with a key tab, a washer, and a nut. Remove all three and then insert the switch from below. Orient the slot on the threads to be on the same side as the 3/32" key hole. Then slip the retaining ring on so that the key tab slips into the 3/32" hole. Slip on the washer and nut and tighten.
  7. The potentiometers also have key tabs but these are on the body of the pot. Remove the washer and nut from a pot, slip it in from below and orient it so that the key tab passes up through the 1/4" key hole. Then put on the washer and nut and tighten.

Top viewof box lid

Underside of box lid

  1. SPDT switch for timeout selection
  2. LED to indicate that the photogate is aligned
  3. SPDT switch for delay range selection
  4. LED to indicate triggering of the delay unit
  5. SPDT switch for selecting sound or photogate input to the delay unit
  6. LED to indicate power on
  7. SPST switch to turn on power
  8. 1-MΩ pot for coarse delay adjustment
  9. 100-kΩ pot for fine delay adjustment
  10. 10-kΩ pot for photogate sensitivity adjustment
  11. 1-kΩ pot for sound trigger sensitivity adjustment
  12. Input jack for microphone cable
  13. Input jack for photogate cable
  14. Output jack to trigger delayed flash
  15. Output jack to trigger delayed camera shutter
  16. Output jack to trigger camera shutter without delay (This can be switched to an instant flash output by changing a breadboard connection.)
  17. Direct sound trigger output for the most rapid response from the sound trigger. This output cannot be used with the Camera Opto-Switch.
  18. Input jack for an external trigger such as a light-activated trigger, a contact closure, or another delay unit.
  19. Pushbutton to test operation of the delay unit.
  20. Jack for AC/DC adapter input

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Wiring the box lid


Some of the components on the box lid are hardwired to each other before making connections to the breadboard. The images below show the wiring from different angles so that you can see clearly what the connections are. Click on the images for larger views. Here are some things to note. (The numbers refer to View 1.)

  • The wires haven't been soldered to the connectors yet. This will come in a later step.

  • White indicates wires that will be connected to ground, and red indicates wires that will be connected to +9 V. While you don't have to use particular colors in your wiring, using a consistent color coding helps keep track of connections.

  • Two white wires are wrapped around the shorter leg of the center LED (1).
  • Two red wires each are wrapped around the longer legs of the outer LEDs (2 and 3).
  • The 1000-ohm resistor (brown-black-red) supplied with the MTE is connected between the shorter leg of one LED (4) and the terminal on the side of the 3.5mm mono jack (5).
  • The 100-ohm resistor (brown-black-brown) supplied with the MTE is connected between the center terminal of the 100k pot (6) and the right terminal (7) of the 1M pot.
View 1 View 2 View 3 View 4


Go ahead and wire the box lid as described above. Next you'll connect components to two of the selector switches.


Wiring the timeout and delay range selectors


Click on the images for larger views.


Timeout selector
Twist together a 1k (brown-black-red) and 100k (brown-black-yellow) resistor as shown. You can use the 1k resistor from the Multi-Trigger breadboard circuit, as you would remove that resistor from the breadboard anyway in a later step. You can use the 100k resistor supplied with the MTE or the extra 100k resistor supplied with your MT-BB.
Connect the untwisted ends of the resistors to the outer terminals of the SPDT switch (timeout selector) on the left (View 1 above). The 1k resistor connects to the left terminal.
Delay range selector
For this, use the capacitors supplied with the MTE. Twist one leg of the 0.047-μf capacitor around the negative leg of the 0.47-μf capacitor. The negative leg is the shorter one. There is also a light blue stripe on the same side of the capacitor as the shorter leg.
Trim the legs and bend them as shown. Go ahead and solder the twisted legs together, as this will make assembly in the next step easier.
The capacitor combination is connected to the SPDT switch adjacent to the timeout selector switch. The untwisted leg of the larger capacitor connects to the switch terminal on the left (1), the untwisted leg of the smaller capacitor connects to the switch terminal on the right (2), and the twisted leg will connect to the shorter leg of the LED to the right (3). This is the leg that has two white wires wrapped around it.


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Soldering some of the connections


You're ready to solder some but not all of the connections. The ones that won't be soldered now are the ones that will have jumper wires attached later to connect to the breadboard. Here are some important tips about soldering in addition to those given previously.


Soldering to the legs of the LEDs: These components can be damaged by excessive heat; therefore, it's a good idea to clip a heat sink to the leg when soldering.


Soldering the switches: Don't hold the soldering iron on the switch lugs too long, as the plastic can melt and break the internal contacts.


Soldering the 3.5mm jacks: The lugs on these jacks bend and break easily. Go easy on them.


Soldering the AC/DC jack: Be very careful not to get too much solder on the lugs so that the solder drips down, particularly on the center lug. If the solder drips down, it can create a dead short between the positive and negative power terminals.


Soldering the RCA jacks and pots: These components have a lot of metal and will take longer to heat up than the other components will. You're not likely to damage a pot but you could soften the plastic in an RCA jack.


About cold solder joints: If you don't heat the metal before soldering the wire, the solder may not bond with it and you can get an open circuit. You can't necessarily tell by looking that you have a cold solder joint. The best approach is prevention by using good soldering techniques. Hold the tip of the soldering iron flat against the metal surface that you're soldering to. Touch the solder to the metal nearby rather than to the soldering iron. When the metal is hot enough, the solder will flow. Flow enough solder on the connection to fill the hole and cover the connection, but don't leave the soldering iron on the metal any longer than it takes to flow the solder. Examine the connection under a magnifying glass. If the solder beaded up, you may not have a good connection.

Click on the photo to the left to enlarge it. The green dots indicate the connections to solder now, and the magenta dots indicate connections that will be soldered later. Hopefully, you'll do a better job than we did and avoid burning the white wires. (We were using a torch and got the tip too close to some of the wires.)

An aside: Here's a problem with writing instructions for assembling kits. After you get most of the way through, you discover that you could have done something differently and better. Case in point, we realized that one of the 470-ohm resistors could be moved from the breadboard to the box lid. This would eliminate one of the jumper wires that will be needed between the box lid and the breadboard. It turns out this is an easy fix.


First, remove the 470-ohm resistor that goes from 1F to the ground row of the breadboard. Then connect the resistor as shown in the photo. One end connects to the tab on the side of the 3.5mm stereo jack. The other end connects to one leg of the pushbutton. Just wrap the bare wire around the wire that connects to the pushbutton. Then solder both connections.


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Preparing the cables


Now is a good time to assemble the cables that you'll need to connect to the box.


Microphone Cable
Here's what you'll need for the microphone cable: the 3-ft length of 2-conductor cable, the 3.5mm mono connector (male), the heat-shrink tubing, and the piezoelectric disc from your Multi-Trigger. Cut the 3/32" heat-shrink tubing into two 1-inch lengths and slip them onto the red and black wires of the piezo disc. Then strip the ends of the wires about 3/4".
From one end of the gray 2-conductor cable, strip the gray insulation back 3/4". Then strip each of the red and black wires 3/4".
Twist the red wire of the piezo disc around the black wire of the 2-conductor cable. Likewise, twist the black wire of the disc around the red wire of the cable.
Solder the connections.
Slip the heat-shrink tubing over the soldered wires and run a lighter or match flame under the tubing to shrink it but not so close as to burn the tubing.
Slip the 3" section of 3/16" heat-shrink tubing onto the cable and over the spliced connections. Heat shrink it into place.
Remove the jacket from the 3.5mm connector and slip it over the cut end of the cable. The threaded end must be toward the cut end of the cable. Strip back the gray insulation on the free end of the cable about 1/4" and then strip the insulation on the red and black wires about 1/8". (Note that another version of this connector has a black jacket rather than gray. Connections are the same for both versions.)
Insert the stripped wires into the holes on the terminals of the 3.5mm mono connector. The red wire goes in the shorter terminal. Don't crimp the metal tabs around the cable yet, as this will cause the insulation to melt when you solder.
Solder the connections. Since there's so much metal, it will take some time for the soldering iron to heat the metal. Hold the tip of the iron flat on the metal to heat it up in the vicinity of where you want to solder. Touch the solder to metal and wait for it to start flowing. This is the way to ensure a good electrical connection rather than a cold solder joint.
Clip off any stray wires and then crimp the metal tabs around the gray cable.
Screw on the jacket, and your microphone cable is complete.

External Trigger Cable

The MTE has a 3.5mm mono jack for an external trigger input. This allows the delay unit of the MTE to be used with any trigger circuit or, in fact, any circuit that provides a short circuit output. The external trigger input can also be used with a simple contact trigger such as the one shown here. If you will be using an external trigger with the MTE, you'll need to provide a 2-conductor cable. If you'll be using a trigger circuit as the external trigger, just use the output cable that came with that circuit. Connect to one end of the cable a 3.5mm mono connector (male) like you did for the microphone cable above. Connect the red wire to the shorter terminal of the connector and the black wire to longer terminal. The other end of the cable will connect to the output of your external trigger circuit.

Photogate Cable

Now let's move on to the photogate cable. The Multi-Trigger comes with two types of photogate cables, the interrupter style and the separate emitter and detector. If you haven't already made up these cables according to the Multi-Trigger instructions, go ahead and prepare the interrupter cable now and test it with the breadboard according to those instructions. Then continue below.

You'll add a 3.5mm stereo male connector to the cut end of the photogate cable. You will have already stripped the wires for connection to the breadboard. However, they're probably stripped too far for connection to the stereo plug. So cut off the stripped wires. Then, before stripping them again, unscrew the jacket of the connector and slip it onto the cable. Now, strip the gray insulation back about 1/4" and the individual wires about 1/8".
The terminals of the connector are numbered in the photo to the left. The black wire will connect to 1, the green wire to 2, and the red wire to 3. If you have trouble getting all the strands through a hole, you can clip off the strands that won't fit.

Here we show two views of the assembly with connections soldered and stray strands clipped.
Crimp the metal tabs around the cable and screw on the jacket to complete the assembly. A second 3.5mm stereo connector is supplied with the MTE kit to attach to the other photogate cable.

Flash and Camera Cables

You should have already prepared a cable for connecting the breadboard to your flash unit using either a PC cord or a Flash-to-PC adapter such as those shown to the left. Next, you'll connect a male RCA plug to the cut end of the cord for connection to project box outputs.
You'll connect the RCA plug to the cut end of the cable. First cut off the free wires, since they'll be too long for connection to the plug. Then unscrew the jacket of the plug and slip it on the cable. If the fit is too tight, snip off part of the ridged sleeve that holds it tightly to the cable. Strip back the gray insulation about 1/4" and then strip the individual wires about 1/8".
Solder the black wire to the longer terminal and the red wire to the shorter one. Crimp the metal tabs around the gray cable.
Screw the jack back on to complete the assembly of the flash trigger cable.
If you're also planning to trigger your camera using a Camera Opto-Switch, you will have prepared for that purpose the cable shown to the left. This cable connects the trigger jack of the Opto-Switch with the breadboard. In order to be able to connect to the Multi-Trigger enclosure instead, add an RCA male connector to the cut end of the cable as you did above. The completed cable for the Opto-Switch will have a male RCA plug on each end (not shown).


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Preparing the breadboard


Some of the components on the breadboard need to be removed to prepare it for connection to the enclosure. (You may have removed the 1k resistor already.) Here is the list of components to remove:

  1. both of the red LEDs
  2. the yellow 1k pot
  3. the white 10k pot
  4. the 100-ohm resistor from 10G to 14G
  5. the 1-kilohm resistor from 22C to 24C
  6. the 0.47-μf capacitor from 23H to 25G
  7. the battery clip

In addition, if there's a wire connected to 13F, remove the wire.


You had removed one of the 470-ohm resistors earlier. So with the components removed, the breadboard should look like the photo below. Click on the photo for an enlarged view. In case you're wondering why the 100k and 1M pots are left in place, the removal of the 100-ohm resistor effectively disconnected them from the circuit. There are also some wires on the breadboard that no longer have a function. However, it's fine to leave them on the board. You may decide later to replace the removed components for testing purposes.

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Adding the battery holder


The photo below shows how the battery holder is connected to the breadboard and the box lid. The numbers in the list below correspond to those on the photo. You can click on the photo for an enlarged view.

  1. A 6" section of blue wire is connected to the upper terminal of the SPST switch (1).
  2. The black wire from the battery holder (4) is connected to the one remaining free terminal of the AC/DC jack (2).
  3. A 6" section of green wire is connected to the same terminal of the AC/DC jack as the red wire (3).
  4. The red wire from the battery holder is connected to the red (+9 V) column of the breadboard (6).
  5. The other end of the blue wire is connected to the ground column of the breadboard (5).
  6. The other end of the green wire is connected to the red (+9 V) column of the breadboard (6).

After making the connections, place a fresh battery in the battery holder. The power LED (7) may come on immediately. If not, flip the power switch the other direction. If the LED doesn't come on with the switch in either position, check your solder joints and make sure that the 1k resistor is connected to the shorter leg of the power LED.


If you have a 9-V AC/DC adapter, plug it into the AC/DC jack. With the power switch on, the power LED should light. If you remove the battery, the LED should remain lit, indicating that the battery holder is automatically disconnected from the circuit when the AC/DC adapter is plugged in.


After verifying operation of the power source, switch, and LED, remove the battery and/or AC/DC adapter. You may want to temporarily disconnect the breadboard so that it doesn't get in the way for the next phase of connecting jumper wires to the box lid.


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Soldering jumper wires to the box lid components


You may notice that the SPST switch at upper right in the photo below is blue, whereas the switch is black in previous photos. During testing of the box, we replaced the original switch. The new switch has a blue base but is identical in function to the previous one.


There will be 15 jumper wires (in addition to the three that you've already attached for the battery holder) to solder to the box lid. One end of each of these wires will be left free for connection to the breadboard later. Before cutting the wires, look at the photo below to see how the box lid will look after soldering the 15 wires. (The wires marked G, Battery holder, and +9 V are the ones you soldered previously when you attached the battery holder.) Click on the photo for an enlarged view. Each of the wires extending from the box is a 6" section. You may want to trim these down later before connecting to the breadboard; however, if you start with 6" lengths, that gives you room for adjustment. You can use whatever colors you want for the wires or you can use the same colors that we used below.


In addition to the wires extending beyond the boundaries of the lid, note also a blue wire extending from the left side of the SPDT switch at point A to the center terminal of the RCA jack at point B. (4th RCA jack from the left) This is another one of those cases where we realized late in the game that there was a way to eliminate one jumper wire by connecting two more terminals on the box. So go ahead and add that wire now. You can solder at point A but wait to solder at point B, because you'll be adding a jumper wire there.



Go ahead and cut your jumper wires now. Strip all the ends about 1/8". Then solder. Remember to use a heat sink when soldering the wires to the LEDs. Note that the green wire at the far upper left is wound around the twisted resistor wires.


When you're finished soldering, clip back the legs of the LEDs and the twisted resistors so that they won't interfere with the final assembly. Also check that the connections on the two legs of each LED aren't touching each other.


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Step-by-step testing


Refer to the photo below to see where the jumper wires connect to on the breadboard. The symbol RaG means the red column next to the blue, ground column. The connections for G, Battery holder, and +9 V are shown in the section, Adding the battery holder. G2 indicates a second wire connecting to the ground column. Don't connect the wires yet, though. We like to connect them in a sequence that allows for step-by-step testing so that if something doesn't work, you can narrow down the problem. To get ready, use something, say a book, to prop the lid up on its side. Place the breadboard on the table beside the lid. You'll be connecting wires to the underside of the lid and also flipping switches and inserting plugs on the other side of the lid. We copied the photo of the top of the lid for convenient reference. Also, we provide a photo showing what the final desktop assembly will look like before closing up the box. Note the arrangement of the breadboard relative to the lid. This arrangement will make it convenient to place the breadboard inside the project box later.

Inside of project box lid showing jumper wires and connections to breadboard

The positions of 28I and 29J were reversed in an earlier version of the photo above. The current, correct version was posted Jan. 26, 2011, 7:45 PM EST.


Top view of box lid

Project box lid with connections of jumper wires to breadboard


Power test

You tested the power LED in the previous section, Adding the battery holder. Make the connections described in that section. Also connect G2 on the breadboard in the ground column but at the opposite end of the column as where G is connected. Insert a battery in the holder, turn on the power switch, and verify that the LED comes on. Then turn off the switch.


Photogate test

Plug in the photogate cable, preferably the interrupter cable since you don't have to mess with alignment for that one. Be sure to plug it in all the way. Connect the jumper wires 8J and 4J to the breadboard. Now turn on the power. The photogate indicator LED should light indicating that the photogate is aligned and the beam is unbroken. Now run your finger through the interrupter. The indicator LED should go out momentarily. If so, all is well to this point. Turn off the power.


Delay unit test

Connect 11E, 13F, RaG, 22C, and 23J. Flip the input selector switch to the PG position. Turn the Coarse Delay pot all the way clockwise. Flip the Delay Range switch (also called Divide delay) to the 0.5s position, and flip the timeout switch to the 1s position. Turn on the power and then push the Test button. After a delay of about a second, the delay unit LED should turn on and stay on for about a second. Now flip the timeout switch to 0.01s. When you push the Test button, you'll get the same delay as before, but the delay unit LED will flicker briefly. It won't be bright. Now flip the delay range switch to the 0.05s position. When you push the Test button, there won't be noticeable delay. Flipping the switch had the effect of dividing the delay by 10. There's still a delay, though, and it would be noticeable if observing high-speed events.


Photogate with delay test

You should get all the same results as above if you break the photogate beam instead of pushing the test button. If breaking the photogate doesn't trigger the delay unit, you may have the input selector flipped the wrong direction.


Delay unit with external input test

Turn off the power. If you have an external trigger that you want to use with the MTE and you've already prepared a cable for it, plug the cable into the external input jack. Then turn on the MTE and test the trigger. The delay unit should function the same with an external trigger as well as with the internal photogate.


If you don't have an external trigger or haven't prepared a cable for it, you can still test the external input. Take the extra 3.5mm mono connector (male) and unscrew the plastic jacket. Insert the plug into the external input jack of the MTE. Turn the power on. With a paper clip, piece of wire, or other metallic object, short together the two bare terminals of the plug. This should trigger the delay unit the same way as pushing the test button. Turn off the power and remove the 3.5mm plug.


Test of delayed flash output

Connect 15B on the breadboard. Then connect the flash cable from the delayed flash output of the MTE to your flash unit. Turn your flash and the MTE power on. You should be able to trigger the flash using the test button or by passing a finger through the interrupter. If you have the coarse delay turned up and the delay range switch to the right, there should be a noticeable delay. Turn off the power and remove the flash cable.


Test of camera outputs

Important: Don't connect a camera shutter or wireless controller directly to either of the CAM outputs. You must use a Camera Opto-Switch with these outputs.


If you're using a Camera Opto-Switch to trigger your camera, do the following test. Connect 18D and 16B on the breadboard. Then connect the trigger cable from the delayed camera output on the MTE to the TRIG jack on the Opto-Switch. Turn on the MTE and your camera and turn the Focus and Shutter switches on the Opto-Switch on. Pushing the Test button on the MTE should trigger your camera shutter after a short delay. Switch the trigger cable to the instant camera output on the MTE. This time, the shutter should be triggered instantly when you press the test button. Turn off the Opto-Switch, your camera, and the MTE.


Test of sound trigger input

Note that the Test button will not light the delay unit LED or discharge the flash when using the configuration described below.


Connect 26A, 28I, 29J, and 30E on the breadboard. Disconnect the photogate cable, and connect the microphone cable to the microphone jack. Flip the input selector to PG if it isn't in that position already. This may seem counterintuitive; however, putting the input selector on PG disconnects the sound trigger from the delay unit for this test. This is important if you're using a flash unit that has high-voltage (>80 V) terminals, as the flash can burn out the 556 timer otherwise. Connect the flash cable to ST OUT. Turn the sound trigger sensitivity pot about three-fourths of the way clockwise. Now turn on the flash and the MTE power. Tap the microphone or snap your fingers. The flash should discharge. In order to adjust the sensitivity of the sound trigger, do the following. Turn the SOUND SENS knob counterclockwise until the flash will no longer discharge. The reason that the flash can't discharge at or beyond this point is because the sound trigger is holding the flash in an on state. Turn the SOUND SENS knob clockwise just enough so that you can discharge the flash again. This adjust the sound trigger for maximum sensitivity. If you wish to have less sensitivity, turn the knob further clockwise.


Note about the limited travel of the sensitivity pot: Occasionally, people will express concern that the sensitivity knob has an effective travel of only about the last 90 degrees of its motion. The 1k value for the pot is a design choice intended to provide the greatest sensitivity for the sound trigger. If, however, one wishes to have greater control and be able to reduce the sensitivity substantially, the 1k pot can be replaced with a 5k pot.


Test of sound trigger with delay

Move the flash cord to the delayed flash output jack. Flip the input selector to the microphone position to connect the sound trigger to the delay unit. Make sure the Delay Range is set to 0.5s and the Timeout to 1s. With the coarse delay turned up, you should get a delayed flash when you snap your fingers. (If you switch the Timeout to 0.01s, you may get multiple flashes for a single triggering event. We've noticed this with a Vivitar 283 flash unit but not with a Nikon SB24 or SB800. In any case, the longer timeout is typically selected when using a sound trigger in order to eliminate multiple images on a single frame.)


This completes the testing. Turn off the power and disconnect the microphone and flash cables.


For troubleshooting purposes, see the circuit schematic.


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Closing up the box and final testing


Lift up the box lid together with the breadboard and slip the breadboard down into the project box. The fit will get more and more snug as you push the box in. Set the battery inside the box beside the breadboard. See the photo below.

You can use the hook and loop tape supplied with the battery holder to hold it firmly in place in the project box. If you have trouble with any of the jumper wires popping out of their holes, you can use hot glue to hold them in place. When everything is ready, gently push the lid down onto the box, making sure that the jumper wires remain in place on the breadboard. You may have to bend the resistor and capacitor assemblies to get them into the box. Once the lid is in place, screw down the lid. Then you can cut the labels and stick them onto to the box as shown below.


Some of our MTE users have provided label templates for the box lid and have given their permission for us to post them for anyone to use. You can use the templates as is or modify them for you own use. Click on the image to download a full-size file. Do a test print for sizing, since the templates may print out different sizes on different systems. You can print the entire template on a sticky label.


Stok MTE template Stok MTE template

MTE template courtesy of James Kelley, USA

Here's a photo of the template mounted on the box.

MTE template courtesy of Erwin Stok, Netherlands



Once you have the box assembled, run through all the tests again to insure that all the wires are still connected correctly.


Reported Issues


We provide here information on issues that have been reported when using the MTE with particular flash units.


Vivitar 283: We mentioned previously that when using the sound trigger with the delayed output, the Vivitar 283 may flash multiple times for a single triggering event. If this happens, setting the Timeout to 1s should solve the problem.


Sigma EF-500 DG Super and EF-530 DG Super: The flash must be set for slave mode in order to be triggered from the hot shoe. When the timeout is set for 1s, the flash goes off repeatedly for a single triggering event when using any input. Setting the Timeout to 0.01s solves the problem.


Operating Manual for the MTE


Possible Modifications


An advantage of a breadboard is that it lends itself to quick modifications. In this section, we provide information on how to make modifications requested by users.


Changing ST OUT to a FLASH INSTANT output

ST OUT is the direct output of the sound trigger, whereas FLASH INSTANT is the instant output of the delayed unit. Either of these outputs is essentially instantaneous save for a small, inherent delay in the circuitry. There may be a bit more inherent delay in the FLASH INSTANT output. One consideration is that when using ST OUT, the flash trigger circuitry must be low voltage; otherwise, the flash can burn out the 556 timer. Here's how to switch ST OUT to FLASH INSTANT.


Open this image. Then simply carry out the steps shown on the image. When you're done, you can use the ST OUT jack to provide an instant flash output for either the sound trigger or the photogate.





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