I have an HJS331 5D and I can't get it to work. It doesn't move and internally makes a clicking noise. Its max is 7.4V its min is 6V. I use a 9V battery for external power, and an Arduino Mega for the data wire. Why is it clicking?
You say it requires 6V to 7.4V so you're using 9V? How does that make sense?
Plus if the 9V you're using is a rectangular PP3 type battery they are useless for running any servos or motors. They can't supply enough current, particularly as you are using a large powerful servo that I would guess needs at least 2A on startup.
A clicking noise is a common symptom of too little power. Try running the servo directl from 4 x AA batteries or a 2S 7.4V Lipo.
Welcome to the forum.
Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html then look down to item #7 about how to post your code.
It will be formatted in a scrolling window that makes it easier to read.
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
Have you got the gnd of the mega and the gnd of the servo supply connected?
As previously advised, you will need a 5V supply capable of at least 1Amp to control the servo.