MATERIALS

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 (potentiometer)

Capacitors: 220μF, 0.1μF

LEDs: green, red

NPN switching transistor

9V battery and battery clip

On/off switch

Momentary push buttons ( 2)

Insulated wire

Heat-shrink tubing

8-pin IC holder socket to let you swap out a bad chip Wireless breadboard/protoboard

Small IC PC board RadioShack part #276-159 Project box

TOOLS

Wire cutters and strippers Soldering equipment 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 stronger wire.

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 (Figure A).

Solder It

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,

Make: 157