Several times recently I have found myself in a situation where I wanted to take a self-portrait, but had no good way to trip the shutter at the right time. I usually use either my wireless remote (2-second delay), or my wired remote (either immediate or the camera’s 10-second delay). The problem is usually that I need several seconds of set-up time, and then have no easy way to access the shutter release.
My solution has been to set the camera on continuous and use the switch on my wired remote to start it off. The biggest problem with that method is that continuous-mode takes a quick burst of images (almost certainly when I’m not yet ready), and then slows down as the internal buffer fills and writes to the Compact Flash card are needed. To complicate this even more, subsequent exposures are at varying intervals, depending on the size of the previous photos and the write speed of the Compact Flash card.
So, I decided I needed a way to trigger the shutter at regular intervals that were close enough together to be useful, but far enough apart to prevent the buffer to fill (it would also be nice if my external flash had time to recharge, but that’s of secondary concern).
I remembered that my Radio Shack Engineer’s handbook had all sorts of projects using 555 timers. Of course, I couldn’t find my copy. It may still be somewhere at UALR. It’s also been out of print for many years. Ebay to the rescue. I found someone who had scanned all the Radio Shack mini-notebooks (ignoring copyright law) and was selling the PDFs for a reasonable sum.
Thus armed, I began my project.
The circuit I needed was already completely laid out:
A trip to Little Rock and Radio Shack yielded most of the parts I needed. The one thing they didn’t have was a breadboard. Only after I was back home did I discover that only one RS in Little Rock stocks them (according to the website). I didn’t want to drive back into Little Rock, but convinced myself to go to Conway instead and visit the store there which had them in stock.
Back home and construction begins. I followed the plan, and lo and behold it worked perfectly the first time!
Now all that was necessary was to get the relay wired to the camera. This introduced another project I had been putting off — a shutter release cable extension. When I first built my wired release I made it far longer than any commercially-available cable. It’s around 40 feet. You would think this would be plenty, but I have on occasion needed it longer. Since Canon uses 3/16-inch, 3-conductor plugs, extension cables seem to be non-existent (at least I haven’t been able to find any anywhere. I didn’t want to build up a single extension cable (of whatever length) and then need more, so I decided on a more extensible solution. I built a short cable and put XLR connectors in the middle of it. In fact, the jack is actually in the shell of one XLR connector.
This gives me the ability to insert a microphone cable of any length into the line. I have Microphone cables anywhere from five to 100 feet.
Now with this in mind, instead of putting a 3/16-inch plug on my intervalometer (I really don’t like trying to solder to plugs that small), I could just use an XLR connector.
I plugged it into the camera and it worked perfectly. The only problem was with the potentiometer specified in the diagram. The usable intervals were in too small a range. I didn’t want intervals measured in minutes. I may replace it with one of a smaller range, but in the meantime have substituted a pair of 100K-ohm resistors (not having a 50K-ohm handy). This gives me a fixed interval of about 4 seconds, which seemed pretty reasonable to me.
The final step will be to transfer the circuit from the breadboard onto a pc board and solder everything in place. I’m saving that for another evening.
