I found a great guide to time lapse photography that covers all the details before and after this Instructable. They mention the use of an "intervalometer" (a new word to me) which can cost $60 to $150 dollars. That's way too expensive for the casual photographer I think. So I made my own!
Step 1: Planning, Schematic, Materials
Here's what this circuit will do. When you turn it on, the camera will get a false signal and take a picture. Then the big capacitor will slowly fill with charge while the green LED is on. How slowly is chosen by the variable resistor. When the cap discharges, the 555 outputs a signal to the transistor which connects the shutter control to ground. The red LED lights up and the camera takes a picture
There are also buttons to use the box as a remote shutter release when the circuit is off.
As you can see you need some stuff. Here's a list:
Resistors: 100k, 470k, 33k, and one 1M variable
Capacitors: 220µF, 0.1µF
LED's: Green, Red
Transistors: NPN-type switching
555 IC timer chip
IC holder socket (to switch out a bad chip)
Protoboard and then later a Radioshack IC PC Board
For Pentax DSLRs, Canon Rebel's, and maybe some others:
Cell phone headset with 3/32" 3 conductor plug (make sure it works, but go cheap)
Soldering and wire stripping tools and such
IC PC Board: $2.49
Handsfree headset kit: ~$5
Other bits and bobs: ~$10
So it all can be had for under $20 and some effort.
Step 2: Prototyping
The tricky part here is attaching the plug for the camera. When you crack open the microphone on your headset, you should see a tiny board like the one below. Your model may vary, but they usually have 3 wires. Those wires control the shutter and focus on your camera. Plug it in to your camera to find out which one is ground, which is focus, and which is shutter. This will be important later, so mark then, or write down which color is which.
When it's time to attach the headset wires to the board, you're going to need to attach them to some stronger wire. If they came coated with blue or red, they will be hard to solder, but persevere with lots of heat, abrasion, and patience and they will connect. Double check the wires work as expected with your camera.
Step 3: Testing
The set of resistors and capacitors in this set up can provide an interval of 30s to almost 2m depending on where the variable resistor is turned to. Set up your camera and prototype and shoot some time lapse.
Keep in mind that a power adapter for your camera will be a big help in the future when you want to capture a whole day in time lapse, but batteries will work for now.
Below is my first attempt with the prototype.
Step 4: Final Build
The buttons are attached to the shutter and focus for some added functionality.
Then you need to drill some holes, solder some wires, and close it up tight.
Easier said then done I know, so here are some tips:
Draw lines on the non-copper side of the board so you can easily connect things correctly
Place your components on the non-copper side so your leads will be easy to solder.
Make sure everything fits before you drill and wire it up.
Tie a knot in the headset cord so you can keep it anchored inside your box.
Use shrink tube and/or tape to over exposed wires
Use as little wire inside as you can stand. It gets real crowded in there.
Step 5: Final Test and Limitations
Ice melting is boring, so I made sure it was a quick frame rate.
What can you use this for?
Ok, so you get what you pay for sometimes. If you went with a manufactured intervalometer, you would get a accurate interval setting. This isn't quite so accurate unless you put a knob on it or something. There is also another slight problem. The camera counts away or a desired length, the "off" time, and then fires off the shutter, the "on" time. It seems that this "on" time can sometimes be too short for the camera to register. Because of this, it sometimes misses pictures. As long as this happens not too often, no big deal I guess. There has to be a solution to this in the circuit that can extend the output pulse, but it's way over my head. I welcome your help on this problem.
Also the buttons don't work while the circuit is on. It would be nice to focus or take extra pictures while the timer is running. Any ideas on that are welcome too.