
I have the simple circuit above. Q1 is a 2n3904.
The purpose is to actuate the shutter on a camera's remote shutter input. Assume that pin D11 is set to logic LOW.
The thing I'm curious about here is if I power the arduino via USB then I get ~30mv vce (multimeter attached to vce).
If I power the arduino with a power brick then I get 1.5v vce, and this seems very strange to me. Notably,
some cameras throw an error if they are plugged in during this state.
If I am powering it with the brick and then ground the circuit to USB (connected to a hub) ground, then vce goes back down to 30mv or so.
I don't understand what is happening here, and I'm unsure of how to process what is happening here. I could use some help troubleshooting this or troubleshooting my assumption that this is erroneous behaviour.
Thank you!