555 IC timer chip
Cheap cellphone hands-free headset with r"
3-conductor plug This will work for Pentax DSLRs,
Canon Rebels, and possibly other cameras.
Resistors: 100kΩ, 470kΩ, 33kΩ, and 1MΩ variable
Capacitors: 220μF, 0.1μF
LEDs: green, red
NPN switching transistor
9V battery and battery clip
Momentary push buttons ( 2)
8-pin IC holder socket to let you swap out a bad chip
Small IC PC board RadioShack part #276-159
Wire cutters and strippers
Hobby knife and drill
across the cap surpasses the 555’s threshold, it
discharges the cap (through pin 7) and outputs
a signal (from pin 3) that makes the transistor
connect the shutter control to ground, triggering
the camera to take a picture. At the same time, the
output lights the red LED and, after a slight delay
filling a 0.1μF capacitor, signals the chip’s trigger pin
to switch the output back and start the cycle again.
The circuit also has button switches that let
you use the box as a remote shutter release when
the power is switched off. We drew the schematic
using the free software ExpressSCH (bundled with
ExpressPCB, expresspcb.com). You can see the
circuit at makezine.com/15/diyimaging_trigger,
where you can also download it as a .sch file so
you can edit it.
Prototype the Circuit
First you need to expose and identify the wires for
the camera plug.
Crack open your headset’s microphone, and
you should see a tiny board with 3 wires. Cut them
free. Camera remotes use 1 wire each for ground,
shutter, and focus. Touching shutter to ground
snaps a photo, like pushing the shutter button down
completely, and touching focus to ground triggers
Fig. A: Intervalometer circuit prototyped on breadboard. The potentiometer (upper right) could be
shortened and could use a knob.
auto focus and auto exposure, like pushing the button down halfway. Turn your camera on, plug in, and
touch pairs of wires together until you know which
wire is which; then mark them or write it down.
Before you go and ruin a perfectly good piece of
perf board (like I did), build and test your circuit on
a solderless breadboard, following the schematic at
makezine.com/15/diyimaging_trigger. The headset
wires are probably too delicate to push into the
breadboard, so you’ll need to attach them to some
Test your camera and the breadboarded circuit
by shooting some time-lapse sequences. I usually
put the camera in position, do the auto focus/auto
exposure once, and then set it to manual focus before starting the intervalometer. The auto exposure
continues automatically on my Pentax K100D; test
yours to ensure the same.
Batteries will work for now, but to capture an
entire day you’ll want to switch to an AC adapter.
With my set of resistors and capacitors, the shutter
interval ranged between 30 seconds and 2 minutes
Now your circuit can graduate to its own board.
I used a mini board from RadioShack that’s designed
for single-chip projects. Five red wires and 1 black
one distribute the power and ground, and otherwise
all the components connect via the printed copper
traces on the bottom (Figure B, next page).
Before soldering, I drew lines on top of the board
to guide my placement of wires and components,