I have setup my camera trigger according to Arducopter wiki pages. I am using pin AN9 and also use ch7 (trigger camera). Good news is if I measure the signal pin of AN9 I can see it goes high (4.65V) when I trigger ch7. Bad news if I connect my relay (HFD23) to ground and signal pin it will not switch relay? The voltage drop falls to about 0.325V with no switching. I only need about 35mA to switch the relay. I tested the relay by just connecting it to 5V and ground on AN9 and it does switch with no problems.
I am now wandering if the port (AN9) is setup correctly during camera trigger to supply enough current? Do I need an external transistor to switch my relay?