I have built a camera controller and I am having issues with activating bulb mode on the camera.
Normal shutter activation works OK.
The controller should follow the following process; open shutter, wait for a sensor to trigger, activate flash, close shutter.
I have this working with a timed exposure (for example 3 seconds) but cannot get it to work with bulb mode.
On the 40D, bulb mode is active while the shutter release is pressed. It works the same way when using a manual shutter release cable. The release cable is a simple contact switch and the shutter is open while ever you are holding the button down.
I have the camera connected to the Arduino via an opto isolator and I had thought that keeping the pin high would keep the shutter open but this is not happening. The shutter is triggering but closing very quickly. I have tested the trigger by using a LED circuit and the LED is lit exactly when it should be so the timings on the pin are OK.
Any suggestion would be greatly appreciated.