While these instructions are for the LAT-BB, the photos all include a delay unit. If you are building the light-activated trigger with a delay (LAT-DU-BB), see these instructions for building the delay unit as well as the light-activated trigger.
The following parts are included with the LAT-BB kit.
Wires 3-ft of 2-conductor cable
3 3" pieces of hookup wire
2" of 3/32"-dia. heat-shrink
3" of 3/16"-dia. heat-shrink
9-V battery cable*
*A fresh 9-V battery is
required but not included with the kit.
You'll also need a wire cutting and stripping tool
such as the one shown to the right. For soldering,
you'll need a 15-30 W soldering iron and resin-core
Click for larger view
Click on the thumbnails below in order to
view full-size images of the breadboard with the components
that have been added in each step.
Using the Breadboard
click to view
The breadboard offers an easy way to build electrical
circuits without soldering. The 2"x3" breadboard provided with
your kit contains an array of holes where wires and components are to
be inserted. The holes in the center portion of the breadboard are identifiable
by row (vertical in the photos) and column (horizontal). There are
two sets of 30 rows numbered by 5's, and each set of rows has 5 columns
labeled A-E and F-J. The 5 holes on each row are electrically connected
to each other (but not across the center channel), so any components inserted
into the same row would be connected just as if they had been soldered.
However, the components can be removed and replaced with other components
at any time, without the hassle of unsoldering and resoldering parts.
On either side of the breadboard are two columns marked by blue and
red lines. The 25 holes in each column are electrically connected, but
the columns aren't electrically connected to each other. The outermost
column marked with the red line at the top will be used for all +9 V connections,
while the outermost column marked with the blue line at the bottom will
used for all ground (negative) connections.
The metal plate included with the breadboard isn't needed for the assembly
Assembling the Light-Activated Trigger
Note that the photographs show
a delay unit already built on the right side of the board. The light-activated
trigger may be used with or without the delay unit. However, the 9-V battery
cable is required for the operation of either kit. This is the cable
coming in from the left with the red and black leads above and below the
555 timer. The column of 25 holes to which the red wire is connected will
be termed the positive column, while the column to which the black wire
is connected will be termed the negative column. While wiring
the circuit, be sure to have the battery disconnected from the battery
click to view
Step 1: Adding the 555 Timer
The 555 timer is an 8-pin IC that also has a notch and circle identifying
Pin 1. (See diagram to the right.) Orient the IC so that the notch
faces the left side of the breadboard. Now find Row 3 and look across
to where it meets Column E. Place Pin 1 there. Pin 8 should easily fit
into 3F. Press the IC firmly down in place; again, it should be seated
across the center division of the breadboard.
click to view
Step 2: Adding
The potentiometer allows you to adjust the sensitivity of your light-activated
circuit. It has three legs, two in the front and one in the rear. Place
the two front legs over 9J and 11J, and the rear leg over the nearest
hole on the nearby positive column. The front legs should be facing the
center of the breadboard, while the rear leg faces the outside of the
breadboard. Press the legs in firmly as far as they will go, but avoid
click to view
Step 3: Adding
Now connect all your electronic components together. Each wire only needs
to be 2 inches in length or less. You can estimate how much you'll need
to bridge across two holes before cutting, although it's always better
to have longer wires than ones that are too short.
Strip about 1/4" of insulation off each end. The list below will tell
you which rows and columns your wire ends should fit into.
3A to (-)
3J to (+)
6D to 3G
7A to (-)
4D to 5G
7E to 8F
*9E to 18F
*This wire is only needed if you're connecting the trigger to a delay
click to view
A = anode (+)
G = gate
K = cathode (-)
Step 4: Adding the SCR
The silicon-controlled rectifier is the output of the light-activated
circuit and can be connected to the input of the delay circuit.
Putting in this SCR is easy since all three leads go in consecutive rows
along Column B. Place the cathode into 7B, the gate into 8B, and the anode
into 9B. The diagram to the right shows the pin designations for reference.
click to view
Step 5: Adding
Locate the brown-black-red resistor (1 kΩ), and insert it
You may wish to trim the leads of the resistor so that it sits closer
to the breadboard. This will reduce the chance that the leads of
two components accidentally touch each other and create a short.
When you add the capacitor in the next step, you may wish to trim its
click to view
Step 6: Adding
Locate the 0.01-µf capacitor (103). Place one leg of this capacitor
into 6H and the other into 8H.
Connecting the Output Cable to Your Flash
If you built a delay unit previously, then you've already prepared a trigger cable to connect the flash to the breadboard. If not, see the information in the yellow box.
A trigger cable is needed to connect your flash unit to the breadboard. The trigger cable kit is purchased separately, since there are different connectors depending on your flash unit. If you need a trigger cable kit, see this page.
Follow the instructions for assembling the flash trigger cable from your kit. (For quick reference, select a link: PC or FA kit / VPC kit.)
Once you've prepared the trigger cable, connect
the wires to the breadboard according to this
Note that HiViz.com trigger circuits can also be connected to a camera shutter or wireless transmitter.
this page for more information.
Step 7b: Preparing and Connecting the Phototransistor
The phototransistor (right) is the light-sensing component
of the circuit. There are two mounting options: directly onto the breadboard,
or soldered to a 3-ft length of the included 2-conductor cable if you
would like more flexibility.
here for assembly instructions, and return here when you are done
with assembly. The free ends of the phototransistor cable will be connected
to your breadboard at the following locations:
Black to 8J
Red to 5J
Breadboard mount: The shorter leg of the phototransistor is inserted into 8J and the longer leg into 5J.
Completed LAT showing connections
to trigger, output, and delay unit
(click to view)
Step 8: Testing
and Operating the Circuit
Note if you're using a delay unit with the light-activated trigger:
For the delay unit outputs, a jumper wire must be added from the output
of the trigger 9E to the input of the delay unit 18F. When using the trigger
without the delay unit, disconnect this latter wire, as some flash units
can burn out the 556 timer if connected to the timer input.
Connect a 9-V battery to the battery clip and a flash unit to the breadboard.
You can now test your circuit. Turn the 100-kΩ potentiometer
to about its midway position. Place the phototransistor as far from the
flash as possible and shaded from it. Shine a flashlight, laser pointer,
or other bright light source at the phototransistor to activate the trigger.
If your flash cable is connected directly to the LAT circuit output or
to Output 1 of the delay circuit, you should notice an immediate discharge
of your flash unit. If your flash cable is connected to Output 2,
you may notice a short delay before discharge, depending on the setting
of your delay circuit. If your flash unit doesn't discharge, try
adjusting the sensitivity. Turn the 100-kΩ potentiometer clockwise
to increase sensitivity.
Note about repeated discharges: A single triggering event can
lead to repeated discharges of the flash. This can occur if the phototransistor
is positioned so that it picks up the light from the flash. This can create
a feedback loop in which the circuit self triggers.A solution is to keep the flash as far from the trigger circuit
as possible. Another is to increase the reset delay if you're using a