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Preparing the photogate cables
There are two types of photogate cables, variable-width and interrupter. Your kit includes parts for one of these types. (The MT3i kit includes parts for the interrupter photogate, and the MT3v kit includes parts for the variable-width photogate.) Instructions for assembling both types are given below.
The variable-width cable has an individual emitter
and detector. This is useful when you need large separations
between the emitter and detector. The interrupter cable uses
an interrupter, which houses the emitter and detector
in a U-shaped plastic housing about 5/8" apart.
This is useful for triggering on the passage of a
drop of liquid.
Variable-width photogate cable
About the variable-width cable
The variable-width cable uses a separate infrared LED emitter
and infrared phototransistor (PT). The LED is
the component with a blue case, and the PT has
a clear case, as shown to the left. For both components,
one leg is shorter than the other. The shorter
leg is positive on the PT, while on the LED, the
longer leg is positive. The figure to the right, courtesy of a helpful DIYer, provides a visual display of the connections that you'll be making to the infrared LED and phototransistor.
Here are the parts you'll need:
3-conductor cable, 3-ft length
Yellow hookup wire, 1.5-ft length
Infrared phototransistor (clear case)
Infrared LED (blue case)
3/32" heat shrink tubing (HST), 4" length
3.5mm stereo plug
Stripping the wires
At one end of the 3-conductor cable, strip the outer casing back
by 9 inches. This will reveal the three inner
conductors, colored red, black, and green. Strip each
of these conductors back by ¾ inches. This
will expose conductors that will be wrapped around
the appropriate component legs later. See Photo 1 showing
the cable after stripping.
Strip both ends of the yellow hookup wire back by 3/4
inches. See Photo 2.
Twist the red wire and one end of the yellow wire
together tightly, as shown in Photo 3.
Fitting the heat shrink
tubing and making connections
Cut the heat shrink tubing (HST) into four 1"
pieces. Place one piece over each wire (black, green,
jumper, red+yellow) as shown in Photo 4, and slide
it back onto the wire. Be on the lookout for pieces
falling off if wires are held upside down.
Make connections by wrapping the
wires around the legs of the PT and LED. When wrapping,
try to get at least two complete turns; more are better.
Before twisting any wires together, make sure the
HST for that wire is still present and hasn't fallen
Make the following connections by twisting the wires
around the component legs.
Twist the green wire tightly around the longer
leg of the PT (clear case) and the black wire of
the 3-conductor cable around the shorter leg of
the LED (blue case). (See Photo 5.)
Twist the combined red+yellow wire around the
longer leg of the LED and the other end of the yellow
wire around the shorter leg of the PT.
When done, your connections should look like those in Photo 6.
Soldering the connections
Trim any stray wire strands on the connections so
the heat shrink tubing will slip over them.
It's a good idea to place a metal clip to serve as
a heat sink between the head of the PT or LED and
the leg where you will be soldering. (See Photo 7.) This will help avoid damage from overheating.
If you don't use a heat sink, complete the soldering
quickly to minimize heat buildup.
The completed soldering job is shown in Photo 8.
Adding the heat-shrink tubing
After soldering, slide the heat shrink tubing over
each of the solder joints so that the legs of each
component are insulated from each other. (See Photo 9.) Keep the pieces about 1/8” away
from the component heads to protect them from overheating
when the tubing is heated.
Using a lighter or a match, move the flame smoothly
back and forth along the entire length of the tubing,
with the tip of the flame just beneath it. (See Photo 10.) If you hold the flame too long in
one spot or too closely to the tubing, you will notice
smoke. If this happens, lower your flame and continue
moving it back and forth.
The tubing will visibly shrink and will be acceptably
tight-fitting after only 10-15 seconds of heating.
Preparing to connect the 3.5mm plug
The photogate cable will connect to the project box enclosure with a 3.5mm stereo male connector. One is shown in Photo 11. The process of adding a connector to the cut end of the 3-conductor cable is described next.
Remove the jacket of the connector and push it onto the cut end of the cable as shown in Photo 12.
Strip the gray insulation back about 1/4" and the individual wires about 1/8" as shown in Photo 13.
Connections to the plug
The terminals of the connector are numbered in Photo 14. 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.
Soldering the connections
Here are some important things to keep in mind about soldering. First, don't crimp the tabs of the shaft around the cable before soldering. If you do, the heat of the soldering can melt the insulation and create a short. Secondly, tin the tip of the soldering iron with solder to improve conductivity. Then hold the tip on the metal near the wire to be soldered. Touch the wire to the metal, not to the tip of the iron. If you don't get the metal as hot as the melted solder, then the solder will bead up rather than flowing, and your connection may not actually conduct.
Photos 15 and 16 show two views of the completed soldering job. Snip any stray, unsoldered wires and make sure that the three conductors do not touch each other at any point.
Completing the cable
Crimp the tabs around the cable as shown in Photo 17.
Screw the jacket on to complete the connector as shown in Photo 18.
The completed cable is shown in Photo 19.
Mounting the cable
Photo 20 shows one method of mounting the emitter and detector. Three sections of 1/2" PVC pipe and two PVC elbows are used. (These parts aren't provided.) A 13/64" hole is drilled through each of the two upright sections of PVC. Then a 1/4" hole is drilled through just the outer part of each section. This allows the emitter and detector each to be slipped through the corresponding hole on the outside without passing all the way through the pipe. Hot glue is used to hold the emitter and detector firmly in the mount. The wires are taped to the horizontal section of PVC. One could also drill a hole through the center of the horizontal section for a mounting bolt for the assembly.
For this cable, the IR emitter and detector are housed in the U-shaped piece shown in Photo 1. In addition to this piece, you'll need the following parts:
3-ft length of 3-conductor cable
3.5mm stereo plug
1-in piece of single strand hook up wire
1 inch of 3/32" heat shrink tubing
Stripping the wires
At one end of the 3-conductor cable, strip the
outer casing back by 2".
Cut the black and green wires 1/4" shorter than the red wire.
Strip the three wires back 1/4".
Cut the heat-shrink tubing into two half-inch lengths. Slip one of the pieces onto the black wire and the other onto the green wire Slip them back out as far as you can.
Soldering to the interrupter
The symbols and on the top view of the interrupter
shown in Photo 4 refer to the LED and phototransistor (PT) respectively.
The numbers refer to the legs on the underside (not
The interrupter has short legs, so you won't be able
to wrap the photogate cable wires around the legs.
Use the procedure described below instead. This works but takes some patience and careful soldering. The procedure is described as if you're working alone. If you have an extra pair of hands to help you, that can make it easier.
Preparing the jumper wire
Strip all the insulation from the 1-in section of hook up wire. (This wire will be used to connect legs 1 and 4.)
Make a small loop near one end as shown in Photo 4.
Thread the loop over pin 1 of the interrupter as shown in Photo 5.
Soldering the jumper wire
Carefully solder the jumper wire to leg 1. The wires will heat quickly, and you won't need much solder for a good connection. Avoid dripping excess solder onto the base of the leg. This can bridge over to the neighboring leg.
Loop the other end of the wire around leg 4 and solder the connection.
The completed jumper wire soldered to the interrupter is shown in Photo 6.
Soldering the black and green wires
For the black and green wires, there's not enough room to loop the wire around the leg of the interrupter. Instead, you'll just lay the wire on the leg parallel to it and solder the connection. See Photo 7.
If you're working alone, it will help to tape down everything with the black wire lying on leg 2. Then touch the solder and iron to the wire just long enough to make the desired connection.
Solder the green wire to leg 3 in a similar manner. The completed soldering is shown in Photo 8.
Soldering the red wire
Loop the red wire around the middle of the jumper wire are shown in Photo 9.
Solder the connection. This one's easy.
Positioning the heat-shrink tubing
Push the heat-shrink tubing down to completely cover legs 2 and 3. This will keep adjacent legs from touching each other. See Photo 10.
Shrink the tubing with the heat from a ligher or match.
Preparing to connect the 3.5mm plug
The photogate cable will connect to the project box enclosure with a 3.5mm stereo male connector. Remove the jacket of the connector and push it onto the end of the 3-conductor cable opposite the interrupter as shown in Photo 11.
Strip the gray insulation back about 1/4" and the individual wires about 1/8" as shown in Photo 12.
Connections to the plug
The terminals of the connector are numbered in Photo 13. 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 are some things to keep in mind about soldering. First, don't crimp the tabs of the shaft around the cable before soldering. If you do, the heat of the soldering can melt the insulation and create a short. Secondly, tin the tip of the soldering iron with solder to improve conductivity. Then hold the tip on the metal near the wire to be soldered. Touch the wire to the metal, not to the tip of the iron. If you don't get the metal as hot as the melted solder, then the solder will bead up rather than flowing, and your connection may not actually conduct.
Photos 14 and 15 show two views of the completed soldering.
Completing the cable
Crimp the tabs around the cable as shown in Photo 16.
Screw the jacket on to complete the connector as shown in Photo 17.
The completed cable is shown in Photo 18.
Preparing the microphone cable
There are 2 versions of the piezo disc as shown below. Use the corresponding version of the assembly instructions. (We started distributing Version 2 in kits on June 8, 2016.)
Begin by cutting the 3/32" heat-shrink tubing into two 1-inch lengths and slip them onto the red and black wires of the piezo disc as shown in Photo 1. Then strip the ends of the wires about 3/4".
Stripping the cable
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" as shown in Photo 2.
Splicing the wires
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. See Photo 3.
Solder the connections. The result is shown in Photo 4.
Adding the heat-shrink tubing
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. See Photo 5.
Slip the 3" section of 3/16" heat-shrink tubing onto the cable and over the spliced connections. Heat shrink it into place. The result is shown in Photo 6.
Connecting the 3.5mm plug
The microphone cable will connect to the project box enclosure with a 3.5mm mono plug. One is shown in Photo 7.
Remove the jacket from the plug 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". See Photo 8.
Insert the stripped wires into the holes on the terminals of the 3.5mm mono connector. The red wire goes in the shorter terminal as shown in Photo 9. 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. Tin the tip of the soldering iron with solder first. Then 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. The completed solder job is shown in Photo 10.
Clip off any stray wires and then crimp the metal tabs around the gray cable as shown in Photo 11.
The completed connector is shown in Photo 12.
The completed cable is shown in Photo 13.
The Microphone Cable (Version 2)
What you need
Use these instructions if your piezo disc is the type shown to the left. This disc has three pins on the bottom labeled G, F, and M.In addition to the disc, here's what you'll need for the microphone cable:
3-ft length of 2-conductor cable
3.5mm mono plug
1 inch of 3/32-in heat-shrink tubing
Stripping the cable
From one end of the gray 2-conductor cable, strip the gray insulation back 2 in. Then strip each of the red and black wires 1/2 in. Cut the heat-shrink tubing into 2 equal sections. Slip one section onto each of the red and black wires. The result is shown in Photo 2.
Connecting the wires
Twist the red wire of the piezo disc around the pin labeled M on the piezo disc, and twist the black wire around the pin labeled G. There will be no connection to the pin labeled F. See Photo 3.
Soldering the connections
Solder the two connections. Photo 4 shows the result.
Shrinking the heat-shrink tubing
Slip the heat-shrink tubing down over the soldered connections. Then run a lighter or match flame near the tubing to shrink it but not so close as to melt the housing of the piezo disc. See Photo 5.
Connecting the 3.5mm plug
The microphone cable will connect to the project box enclosure with a 3.5mm mono plug. One is shown in Photo 6.
Remove the jacket from the plug 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". See Photo 7.
Insert the stripped wires into the holes on the terminals of the 3.5mm mono connector. The red wire goes in the shorter terminal as shown in Photo 8. 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. Tin the tip of the soldering iron with solder first. Then 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. The completed solder job is shown in Photo 9.
Clip off any stray wires and then crimp the metal tabs around the gray cable as shown in Photo 10.
The auxiliary input allows the delay unit of the Multi-Trigger 3 to be used with any HiViz.com trigger circuit or, in fact, any circuit that provides a short circuit output. The auxiliary input can also be used with a simple contact trigger such as the one shown here.
Parts for an auxiliary input cable aren't included in the kit. In order to prepare such a cable, simply add a 3.5mm mono plug to one end of a 2-conductor cable like you did for the microphone cable above. The other end of the cable will connect to the output of your external trigger circuit. The connector that you use for that end will depend on the external trigger that you're using.
Preparing a trigger cable
A flash trigger cable isn't provided with the MT3 kit, because there are different methods of connecting to a flash unit. You may have purchased one of our trigger cable kits to use with the MT3. If so, follow the online instructions for your kit to prepare the cable. Three versions of completed trigger cables are shown below.
PC plug to 3.5mm plug
Hot shoe adapter to 3.5mm plug
Vivitar 283-type plug to 3.5mm plug
Testing the Inputs and Outputs
We assume for the following that you've already assembled the control box and successfully completed the timing tests. You will also need to have a battery installed in the control box or be using a 9V AC/DC adapter.
We recommend having the control box turned off whenever you insert or remove plugs.
Turn the Sensitivity knob to 5 and the other knobs to their lowest settings. Flip the input selector switch to PG. Plug in the photogate cable to PG In. Be sure to push the plug in all the way. Now turn on the Multi-Trigger. If you're using a variable-width photogate cable, point the emitter at the detector several inches apart and tape them down to prevent movement. If you're using an interrupter cable, the emitter and detector are perpetually aligned. The PG Align LED should light indicating that the photogate is aligned and the beam is unbroken. Now disturb the alignment or run your finger through the interrupter. The PG Align LED should go out while the beam is broken. The Start and Finish LEDs should flash briefly, indicating that the delay circuit was activated.
In order to test the Sensitivity control, turn the knob clockwise. At some point, the alignment LED will go out. What you've done is make the circuit so sensitive that it triggers spontaneously. If you turn the knob back a bit, you can set the photogate in its most sensitive working condition. You'll find that this setting depends on the separation of the emitter and the LED as well as the ambient light.
If the photogate test didn't work, do the following.
The first thing to check is the plug. Make sure the plug was pushed in all the way. If so, unscrew the plastic jacket on the plug and inspect it to make sure that the wires are connected to the correct terminals and that none of the wires are in contact with each other.
If the plug looks good, you can check for the operation of the photogate circuit without the cable in place as follows. First remove the cable and open the box. With the power to the box turned on, touch the ends of a wire between terminals 2 and 3 of the photogate jack. If the PG alignment LED comes on, that indicates the photogate circuit is working correctly and narrows the problem down to the photogate cable. In that case, double check all your wiring for the cable.
If, when you short terminals 2 and 3 according the previous test, the PG alignment LED doesn't come on, that indicates a problem with the photogate circuit. Check to make sure that the 555 timer has the correct orientation in the socket on the PCB and is fully seated. Make sure that you've soldered all connections to components on the box lid and that the connections are good. One way to check for bad connections is to wiggle the wires while the unit is on to look for erratic behavior. Also check connections of the jumper wires to the PCB and check that the alignment LED is connected with the correct polarity. Here's how to check the LED.
First, turn off the box. You'll need some clip wires, a 9V battery, and the extra 1-kΩ resistor provided in your kit.
Connect the positive terminal of the battery to the resistor, and connect the other end of the resistor to the positive leg of the LED. Then connect the other leg of the LED to the negative terminal of the battery.
If the LED lights, then the polarity is correct. If the LED doesn't light, then the easiest thing to do is replace the LED rather than trying to rewire it.
If you're unable to get the photogate working, you can still test the sound trigger.
Photogate with delay test
If, when you tested the photogate, the Start and Finish LEDs also lit up, that indicated that the photogate connected successfully with the delay circuit. If the Start and Finish LEDs didn't flash, then the problem is most likely with the input selector switch. Inspect the connections between the switch and other components. Try to wiggle the terminals of the switch. If there's any motion, that can indicate that an internal contact has been broken. This can happen if the switch is overheated during soldering. In that case, you will need to replace the switch.
Sound trigger test
If the previous test revealed a bad switch, then you'll need to replace the switch before moving on to the following test. When you're ready, remove the photogate cable and connect the microphone cable to MIC In. Flip the input selector to SND. Snapping a finger should trigger the Start and Finish LEDs.
If the sound trigger test didn't work but you know that the delay unit works by itself as well as with the photogate, that indicates a problem with the sound trigger. Test the microphone cable first. Unscrew the plastic jacket around the plug and check whether the wires are coming into contact with each other. If the plug looks ok, check the internal wiring of the box as described previously. Also check that the PN2222A transistor is oriented correctly on the PCB.
Testing the Flash and Camera Outputs
You don't need to have a trigger cable connected for the following tests; you can use the Test button instead, but make sure that the Input Selector is in the SND position. Connect your flash unit to the Instant Flash output. When you press the Test button, the flash should discharge. Do the same with the Delayed Flash output. Turn the Coarse Delay up high in order to make the delay noticeable. Now turn the delay down to 0 but turn the Timeout to 1 s. Press the Test button twice in quick succession. The flash should fire with the first press but not the second. The Timeout suppresses the second triggering as long as it comes within the 1 s timeout interval. Try pressing the Test button twice more than a second apart to see this.
If your flash unit's synch circuit is low voltage (less than 80 V), you can also use it to test the camera outputs. Caution: Flash units having high-voltage synch circuits may burn out the camera outputs. If you're not sure whether your flash unit has a high-voltage synch circuit, don't connect it to the camera outputs.
Some flash units require a low-voltage pulse in order to fire. If you have such a unit, plug it into the Delayed Pulse output to test it.
If you have the shutter cable for your camera, you can test camera triggering. Connect the shutter cable to either the Instant or Delayed Camera output. Set your camera for manual focus and press the Test button. This should actuate the shutter.
If any of the output tests failed even though the Start and Finish LEDs lit as expected, that means there is a problem either in an output stage of the MT3, the cable connecting the MT3 to the flash or camera, or the flash or camera itself. Try these things to troubleshoot.
For the camera outputs: The shutter cable is not likely a problem, but the camera shutter may require that the output remain high for a longer period of time than normal. If you didn't try testing with the Timeout turned up high, do that. Note that the Timeout only applies to the delayed outputs. Therefore, connect your camera to that output. Also be sure that your camera is set for complete manual operation. If the problem persists, open the box and check to make sure that the PS2501-4 optocoupler is seated firmly and in the correct orientation. Also check the solder connections to the camera output jacks.
For the flash outputs: Set your flash for manual operation. Also, check the flash trigger cable by removing it from the MT3 and then using a paper clip to short the contacts on the plug. This should discharge the flash. If it doesn't, that indicates there's a problem with the cable. In that case, check the wiring of the cable. If you have a continuity checker, you can also check the two conductors of the trigger cable for continuity. If the cable is fine, then open the MT3 box and check that SCRs 3 and 4 have the correct orientation. Also check the solder connections to the flash output jacks.
This completes testing. If you have problems that you were unable to resolve, you may contact us and we'll do our best to troubleshoot by email.