"Circuit design is always a question of trade offs.  If the output impedance of the pixhawk was higher (i.e. current limited) then the value of R1 (the one limiting base-emitter current) would matter.  And if the input impedance of the camera's USB…"

"Did you try the original resistor values without the LED ?
If you want to use the LED,  drop the value of R1 to something between 6K and 10K.  That will get you a lot more current through the LED & R2 and a bigger voltage drop."

"You should see almost 5V at the USB connection. You don't need to connect the camera.   Please draw and post another diagram - this time of the exact circuit you constructed?
Also,  try the original circuit (without substitutine the LED and 1K…"

"That's pretty much what I would have expected to see based on basic transistor theory."

" Reply by Sandy Sound 9 hours ago

And is it possible to add an LED to show it is receiving/passing signal!



If you want to add an LED, change R2 to 1K ohms and put the LED in series with it.  Connect the camera across the combined R2 & LED…"

"I don't believe that will work as your have drawn it.   All of the circuits published so far depend on you driving the transistor into saturation ( Collector to Emitter voltage drop approaching 0v) by driving enough current into the base.  That…"

"The circuit that uses two transistors ( BC547 &  BC557 ) is needed when the camera ground (0V) must be at the same potential as the pixhawk.  Apparently Sony cameras need this while Canon Powershots do not.  So the Powershots can use a "floating…"

"At the low voltages involved ( 5V or less ) either transistor will work fine.  If you don't want to wait for a BC557 to arrive,  then the single transistor circuit shown <at this link> will work with your S100."

"Thanks for that note.  That means the total cost to someone on the west side of the Atlantic comes to about $115 US$ then."

"Nice looking solution.
But at $75 US$ (plus international shipping) it's going to be a lot more expensive than the simple one or two transistor DYI solutions proposed here.  Still,  there is some value to a pre-built solution.
Unfortunately,  it…"

"I don't think there is anything you can do to make that Sparkfun board give a nice clean 5V output.

This might help if you what a commercial solution : PixHawk Camera Trigger Cable  (scrol down to the PixHawk Camera Trigger Cable)"

"I do not think that sparkfun board is likely to work. It needs to draw more current from the 3.3v output of the pixhawk than the pixhawk can source.  So the output will not go to 5V when the pixhawk tried to "shoot".
I have not tried it but…"

"The Canon S100 will only shoot at 2 pictures per second if you put the camera into "Continuous Mode' using the Canon shooting menu.   But be aware that when you do that, the camera sets exposure and locks focus on the first shot and all subsequent…"

"You are not right.

I think what you are referring to is the use of the new Canon DIGIC6 chip in some of the newer Canon high end models and the DIGIC4+ in some other models.    The DIGIC4+ has been hacked in several camera models and there is at…"

"The link still works.  Or you could start here KAP UAV Exposure Control Script"

"Actually,  while setting the output type to CA-1 is wrong for what you are doing, it also will not hurt.  When CHDK is running a script, the USB remote setup values for input and output types in the CHDK menus are ignored."