Possums: Deterring or getting rid of them

I bought one one these traps and over two days got three possums, bugger all since (over a year). I must be doing something wrong, but I don't know what.

Looking round for ideas to keep possums away from a new orchard and the veggie garden I came across this in the states.

http://niteguard.com/

Its a solar powered red flashing LED, about US$20, so I converted a solar light to flashing LED and it seemed to keep animals away from the veggie garden. The idea was to make a few more, when in Bunnings Botany ($21) I spotted a solar powered spot light, which activated upon movement, but it had a small 24 hour flashing red led. I guess it was supposed to mimic a security camera. I mounted 2 on opposite sides of my orchard, and up 'til now no problems, not from possums anyway, the strong wind is another story! To finish this off Trade Tested were selling a solar powered flashing light pipe for $20, so I attached one to the fence for good measure.