My latest time-lapse camera rig, was failing to run due to the constant ground connection on the camera power input.
This is an off-grid, solar-powered rig, combining a Raspberry Pi and an Arduino, to share tasks using a minimum of energy.
As a novice in electronics I felt I was making progress, having used GPIO controlled relays to break the positive wire connection on several of my rigs.
However, in this rig, I use two different methods to take the pictures:
1/ An in-camera script (C.H.D.K. Canon Hackers Development Kit) which takes a picture automatically, on power up of the camera by the Arduino,
2/ A PTP connection to the camera's USB port when the Raspberry Pi is active and supplying the power to the camera as well.
Due to the ground wire of the Raspberry Pi remaining connected to the Camera power input, I found that my on-board script failed, due to it falsely detecting a USB connection. On disconnection of the ground wire, the script works as intended.
I imagined this need for 'double disconnection' ie. of both the positive AND negative wires, would be a common issue in electronics and that there would be a relay component ready made for the job but Google doesn't turn one up.
I suspect I simply just don't know the right name for the task, among the many versions of relays out there.
Please advise, or, if there's another approach in circumstances like mine, I'd love to hear it. it seems wasteful to be using a two channel relay to operate a single power switch. ie. one channel for the positive wire and one for the ground. I hope I explained myself well enough. If not, I apologize and will correct as best I can Thanks in advance