creating signal to award badge

I have a new simple badge something like badge for first 10 karma points. I have put together the badge by following the existing method. But now the problem is awarding the badge. I am not sure how I should create the signal.

What I did was following: I add the following to user_moderate_user_reputation

if reputation_change != 0:
    award_badges_signal.send(None,
        event = 'reach_10_karma',
        actor = user,
        context_object = user,
        timestamp = timestamp
    )

I thought the signal needs to be called every time the reputation changes to check the award. But this was not successful. What is the best way to implement this?