DIY

IMAGING

DSLR TIME-LAPSE TRIGGER

Shutter-control “intervalometer” uses a 555 timer chip. By Chris Thompson

Many digital SLR cameras use r" 3-conductor jacks for their remote shutter/focus control ports, which means they accept the same plug that’s on cellphone headsets. I used this knowledge to hack a cheap hands-free phone kit into a remote shutter release for my camera, for taking long-exposure HDR (high dynamic range) photos. Later, I found a 555 timer-chip tutorial online and realized how great it would be to automate the shutter to do time-lapse photography.

Then I read Photojojo’s ( photojojo.com) “Ultimate Guide to Time-Lapse Photography” and learned that the intervalometers most cameras require to trigger their shutters cost $60—$150. I think that’s way too expensive for casual experimentation, so I made my own for less than $20.

I’m not too great with designing electronics from scratch, so my friend Michelle Kruvczuk helped

156 Make: Volume 15

me with the schematic. It’s based on a 555 chip, which has 2 input pins that work in tandem: the trigger pin (pin 2) sets the chip’s output high when its input becomes low, and the threshold pin (pin 6) sets the output low when its input becomes high. By charging and draining a capacitor connected to these inputs, you can make a 555’s output oscillate between low and high.

Add resistors of different values to control how fast the capacitor fills and empties, and you can determine the timing of the cycle. With a variable resistor (potentiometer), you can adjust the timing by turning a knob.

The circuit for this project uses a slow cycle to pause between shutter firings. The current slowly trickle-charges a big 220μF capacitor while lighting the green LED; how slowly is determined by turning the knob on the variable resistor. When the voltage

Photography by Chris Thompson