The delay unit can be used
with a variety of trigger input circuits to discharge a
flash unit after a selectable time delay. The assembly
instructions for the delay unit are given below. For
instructions on adding trigger inputs, go to these pages:
Capacitors 2 0.0047-µF (472 or 0047)
1 0.01-µF (103)
2 0.047-µF (473 or 047)
1 0.1-µF (104)
1 0.47-µF (cylindrical metal case)
1 10-µF (cylindrical metal case)
Wires 3-ft of 2-conductor
9-V battery cable2
1We are now providing 2 additional 1-kΩ
resistors with delay units. This is to address an issue
with some Canon flash units. The use of these resistors
is described in Step 5.
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.
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)
Constructing the Delay Circuit
click to view
1: Adding the 556 Timer
The 556 timer is an integrated
circuit (IC) with 14 pins that need to be seated in
the breadboard. Look at the top of the IC (with
pins held away from you) and locate the semicircular
notch at one end. The locations of pins 1 and 14 are
shown in the figure to the right. Pins 1-7 are numbered
consecutively right-to-left, and pins 8-14 are numbered
consecutively left-to-right. Face the notch toward
the right of the breadboard so that Pins 1 and 14
are also facing to the right. Now find Row 27 and
look across to where it meets Column f. Place Pin
1 there. Pin 14 should easily fit in Row 27, Column
Don't press the IC down
until all the pins are lined up with holes. Once they're
lined up, press as evenly as possible across the top
of the IC in order to make sure that none of the pins
are bent as the IC is seated. Press firmly to
make sure the pins go in as far as possible.
click to view
2: Adding the Potentiometer
potentiometer (blue knob) allows you to adjust the
time delay of your circuit. It has three legs,
two in the front and one in the rear. Place the two
front legs over Rows 28 and 30 on Column j, 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 is facing the
outside of the breadboard. Press the legs in firmly
as far as they will go, but avoid bending them. (Note
that in the connections to follow, the left leg will
not be connected to anything else.)
click to view
3: Adding the SCRs
= anode (+)
G = gate
C = cathode (-)
rectifiers (SCRs) labeled EC103D are the output stages
of the delay circuit. The SCRs allow you to to discharge
a flash with or without a delay. To identify
the leads of the SCR, hold it as in the diagram to
The two SCRs fit into
consecutive rows on Column a, except for their cathodes,
which should fit into the nearest available hole in
the negative (blue) column. Here's what to do. Insert
the gate of one SCR into Row 15 of Column a, and the
anode into Row 16 just beside it. The cathode goes
to the negative column. Next, insert the gate of the
other SCR into Row 17, and its anode into Row 18 just
beside it. Its cathode will also go to the negative
click to view
be concerned if some of the capacitors shown in
the photo have different physical sizes from those
in your kit. What is important is that the
numbers on the capacitors are correct.
4: Adding the Capacitors
First, gather together all the capacitors.
You should have 8 total. All but two of them have
round, tan heads. The other two have cylindrical
heads. These are the electrolytic capacitors, and
unlike the others have polarity. Look at the cylindrical
case and find the light-colored strip bearing a negative
sign. The lead on the side of this strip is the negative
lead, while the other lead is the positive lead.
Note that this is also the longer of the two leads.
Locate the 10-µF electrolytic capacitor,
which will have 10 µF written on its case. Insert
the positive lead into Row 26, Column a. The negative
lead will go to the nearest hole on the nearby negative
column. Now locate your 0.47-µF electrolytic capacitor.
Insert the positive lead into Row 27, Column j, and
insert the negative lead into Row 25 of that same
column. (See this note
regarding a a discrepancy between these instructions
and the circuit schematic provided with the kit.)
That's it for electrolytic capacitors.
Now let's do the other capacitors. Locate the two
capacitors labeled "472" or "0047." These
have values of 0.0047 µF. Take one and insert one
end (it doesn't matter which this time) into Row 19,
Column b. Insert the other end into Row 21 of that
same column. For the other 472 capacitor, insert one
end into Row 18 of Column i, and the other end into
Row 22 of that same column.
Finally, locate the two capacitors
labeled "473" or "047." These have values
of 0.047 µF. Take one and insert one end into Row
25, Column g, and the other end into Row 29 of the
same column. Insert one end of the next capacitor
into Row 24, Column c. The other end should reach
over to the nearest hole of the negative column.
You should have two capacitors remaining.
The 0.1-µF capacitor and one of the 0.01-µF capacitors
may be substituted for the 0.47-µf capacitor in order
to obtain different delay ranges. This will
be discussed in Step 9.
You may wish to trim the leads of
the capacitors so that they sit 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 resistors in the next
step, you may wish to trim their leads also.
click to view
5: Adding the Resistors
Each resistor is marked with four
bands that are a code for the value and tolerance
of its resistance. You should have 8 resistors; lay
them out so that the gold band on each is always facing
right (so it's the fourth band). The colors should
now be read from left to right, ignoring the gold
band. In the following instructions, the resistors
will be identified by the first three bands, ignoring
the gold band. The gold band indicates the tolerance
of the resistance value, while the other three bands
indicated the value of the resistance.
There are 4 resistors with
the color code red-red-orange. These each have
values of 22 kΩ.
Insert one end of the first into Row 15, Column d,
and the other end into Row 19 of the same column.
Insert one end of the second into Row 21, Column a,
and the other end into Row 30 of the same column.
Insert one end of the third into Row 17, Column c,
and the other end into Row 22, Column c. Lastly, insert
one end of the fourth into Row 22, Column g, and the
other end into Row 24, Column j.
users of Canon flash units 430ex and 580ex.
In order to correct a problem in using these
flash units with the delay circuit, substitute
resistor (black-brown-red) for the 22-kW
resistor for the these two resistor placements:
to 15d and 22c to 17c.
Locate the brown-black-red
resistor (1 kΩ). Insert one end into Row
26, Column b, and the other end into Row 30 of the
Locate the brown-black-green
resistor (1 MΩ); insert one end into Row 18,
Column j, and the other end into Row 22 of the same
Locate the brown-black-brown
resistor (100 Ω); insert one end into Row 26,
Column h, and the other end into Row 30 of the same
The one resistor remaining,
the brown-black-yellow resistor (100 kΩ),
can replace the brown-black-red resistor (1
kΩ) later if you desire a greater reset delay.
This will be described in Step 9.
click to view
6: Adding the Wires
Now you'll add wires to 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, though it's better to have longer wires than
ones that are too short. Note that the wires supplied
with your kit won't necessarily be the same color
as those in the photographs.
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. The longest
wires are listed first so if you happen to cut a piece
that's too short, you'll be able to use it later.
(1 inch or less)
30, Column e
23, Column c
27, Column c
21, Column g
27, Column d
30, Column d
29, Column f
25, Column d
Row 26, Column d
24, Column i
26, Column g
27, Column g
19, Column e
23, Column g
click to view
7: Adding the Battery Clip
Locate the battery clip. Insert
the red wire into the positive column and the black
wire into the negative column. Don't attach
the battery yet.
to Output 1 for quick discharge; click to view
Cable to Output
2 for delayed discharge; click to view
8: Connecting the Output Cable
The 3 feet of 2-conductor cable may
be used to connect either of the circuit's two outputs
to the PC cord of a flash unit. Output 1 provides
an almost immediate discharge, while Output 2 provides
a delayed discharge. You’ll need to provide your own
From one end of the 2-conductor cable,
strip 1" of the gray insulation, being careful not
to cut the insulation on the red and black wires.
Then strip 1/2" of insulation from each of the
red and black wires. These will connect to the
breadboard. Next, strip 2" of the gray
insulation from the other end of the cable.
Strip each of the individual wires back 1".
These will connect to the PC cord. One way to
make this connection is to cut the socket off the
end of the PC cable, strip the insulation on the individual
PC wires back by 1", splice the red wire of the
gray cable to the positive wire of the PC cable, and
splice the black wire of the gray cable to the negative
wire of the PC cord. (The positive wire of the
PC cord is usually the wire that goes to the center
pin of the PC socket. For more information on
connecting to a PC cord, see this page: http://hiviz.com/tools/triggers/makeown.htm#connect.)
If using Output 1, insert the end
of the red wire on your ½" end into Row 16, Column
b, and the end of the black wire into the nearest
hole on the negative column. If using Output 2, insert
the red wire into Row 18, Column b instead.
A sample jumper cable from input to ground;
click to view
9: Testing and Operating the Delay Circuit
testing the circuits, double check that all components
are connected in the correct locations and with the
correct polarities. Some wiring mistakes can cause
the 556 timer to burn out.
In order to test your delay circuit,
its input can be shorted to ground. First, connect
your flash unit to Output 1 and connect a fresh 9-V
battery to the battery clip. Then take a piece of
wire and insert one end into Row 18, Column h.
(We'll call this the trigger wire.) Insert the other
end to the nearest hole on the negative column (ground).
The flash should discharge immediately. Now disconnect
one end of the trigger wire, and connect your flash
to Output 2. Connect the trigger once again. The flash
should discharge, but there may be a slight delay
before it goes off. Increase the delay by turning
the blue potentiometer counterclockwise. Disconnect
and reconnect the trigger wire to test again. The
further counterclockwise that you turn the potentiometer,
the more of a delay that you should notice.
Note, however, that in the furthest counterclockwise
position, the circuit may not respond. If that's the
case, back off a little from the maximum position.
If the delay unit doesn't discharge the flash unit,
there are a number of things to check.
Make sure the battery
Check whether the
polarity of the cable to your flash unit is reversed.
This can be done simply by reversing the cable connections
on the breadboard. This won't damage the circuit.
Double check that
the polarities of the electrolytic capacitors are
correct, that all components are connected in the
correct locations, and that all wires and components
are firmly seated in place.
Make sure the potentiometer
is seated completely in the breadboard. Try pushing
down on it gently while testing the circuit. If
this is the problem, you may want to solder some
wire legs onto the potentiometer so that the wires
make secure connections with the breadboard contacts.
If there were wiring
mistakes, it's possible that the 556 timer is burnt
us for a replacement 556 or check to see if
your local electronics store carries the component.
Changing the delay
range: A half second delay is long for
many high-speed photography situations. You
can change the range of the potentiometer by removing
the 0.47-µf capacitor and replacing it with one of
smaller value. Extra 0.1-µf and 0.01-µf capacitors
have been provided for this purpose. The 0.1-µf
capacitor will provide delays up to about a tenth
of a second, while the 0.01-µf capacitor will provide
delays up to about a hundredth of a second.
Changing the reset
delay: After the flash unit discharges, it
will be inactive for a short time before it can be
discharged again. This amount of time is termed
the reset delay. The circuit is currently set
for a reset delay of about a hundredth of a second.
(This is actually less than the recharge time of most
flash units.) For some photo situations, this
may lead to multiple exposures. In order to
increase the reset delay, first locate the 1-kΩ
resistor. Then replace it with the 100-kΩ resistor.
This will increase the reset delay to about a second.
If you're using a sound
or photogate trigger as an input to the delay circuit,
you would connect the positive output of the trigger
to Row 18, Column g and the negative output of the
trigger to the negative column (ground). More details
are provided in the instructions for building these