Canon EOS Rebel Remote Control Information
Most Canon EOS Rebel and Digital Rebel series cameras include a wired remote control interface that can be used to remotely activate the camera's autofocus lock and shutter release. The remote switch connects to the camera with a 2.5mm stereo phone plug and works like a remote cable release would on a manual camera, using electrical instead of mechanical transmission. Pinouts, a list of commercial products using this interface, and instructions for building custom switches are described here.
This page does not specifically describe the proprietary "N3" connector used by Canon's professional DSLRs like the 1D and 10D-50D, although most of this information, excluding the physical connector, probably applies to it as well.
The remote switch connects to the camera through a 3-wire cable terminated at the camera side with a 2.5mm (aka 3/32") 3-conductor (aka stereo or TRS) phone plug (aka audio plug). This physical connector is the same one used by, for example, Texas Instruments graphing calculators and some phone headsets and cassette recorders. The switch cable plugs into a female jack on the side of the camera.
The three conductors—tip, ring , and sleeve—are used for shutter release, autofocus, and ground respectively. The switch connects sleeve to ring to start the autofocus lock, and sleeve to tip to signal the shutter to open.
Since TRS connectors are prone to shorting between contacts when the plugs are inserted and removed, the camera should be turned off when cables are connected or disconnected. Nothingbad will happen though, other than wasted "film."
On Canon's RS-60E3 remote, the autofocus and shutter are controlled by a two-stage switch configured so that the shutter cannot be triggered without the autofocus switch first being closed, copying the behavior of the built-in shutter button. Although the camera will respond to a shutter switch closure even if the autofocus switch is open, the bulb mode handling is slightly counterintuitive: If
the autofocus switch is used, the shutter will open
when the shutter switch is closed but will close
when the autofocus switch is opened. Coupling the switches somehow so that the shutter release forces the autofocus closed can prevent unexpected shutter closures, although autofocus and bulb are probably not used together most of the time.
Several commercial remote switches and other devices such as self timers and intervalometers are avaialable from Canon and other manufacturers.
Canon's RS-60E3 is the standard model, which allows operating the autofocus and shutter controls from a lengthy 2 feet from the camera (make sure your lens is long enough so you'll actually be able to see yourself!).
Opteka also makes a similar wired switch, as well as a wireless RF model. More advanced models are available from various manufacturers with timer or intervalometer functions.
Due to the simple electrical interface, unnecessarily high cost of many commercial switches, and the possibility of using different kinds of sensors with the camera, many people have built their own remote controls.
To trigger the camera from an electronic signal, a relay should be used. In theory, a transistor can be used to short the signal and ground lines, however, a relay is a better choice since it is guaranteed to work for any circuit that can be triggered by a mechanical switch (since the relay contacts are
a mechanical switch). The NXTPanoramaStepper
use relays to signal exposures.