So I am creating an AirSoft Gun turret and now I need to control its movement. That means I need roughly 210 degrees of movement on the z axis and 90 degrees on the y axis. At first I thought of using a stepper motor for this project due to the possiblity of the continuation of this project into a larger system but when I found out about drivers I pretty much throw that idea out the window. The next thing I went into was server motors but I was having issue’s determining what my power requirements were. So Basically I am asking for your guys help on determining a few things.
First off. If I were to go with stepper motors I have a couple of issue’s.
Driver boards. I looked into both the EasyDriver and The BigEasyDriver but I am unsure due to the number of complaints about the new boards even though they claimed to fix the silk screening issue’s. This isn’t a big issue due to the wide range of other drivers and suppliers but compatibility issue;'s are confusing me.
Power supply most of these motors require powers that seem to larger than standard for most wall warts and I am unsure on how to go about powering the drivers. I understand what to do once I can get power to the board but I am unsure on how I could find pretty much anything above 12v capible of more than 1Amp.
For Servo’s I have pretty much the same concerns but focusing more on continuous motion and determining how power of one I will really need.
What I really need from people that know what they are doing (You Guys smiley-razz) . Is what configuration would work best for me. I can set my Base up so that the motor controlling the twisting will not have any weight one it. (placed below rotating platform just turning the platform on wheels.) So that shouldn’t need anything crazy powerful. My issue is I am uncertain what kind of power i will need for the tilting . I don’t really want to do any gearing here and I don’t expect my turret to be holding a position for more than 5-10 seconds.
Finally the Power supply. I have found a couple instrutables on how to run the stepper motors and set them up even but I haven’t really seen any that have mentioned power supply systems. I understand this is probably because they are all a little different and totally hacked out.
So that whole long monologue about me being confused boils down to. What motor do I need, what driver do I need, and how do I power the driver.
First thing to do is figure out how fast you want the AS “turret” to move. This might be a set of number for Azimuth and Elevation saying the servo’s must go from point to point in some X, Y secs. This will be important in choosing how powerful the motors must be. Another set of numbers you’ll want some sort of handle on is how accurate the pointing must be. If you tell the turret to go to X and Y deg, just how close to X and Y is good enough ? +/- 0.1 deg ? +/- 0.5 deg ?? You already have the range of movement needed.
Next would be to do some preliminary design work. You’ll want to put the AS gun balance point (front to back) on the elevation axis of balance. That way the servo isn’t fighting gravity to keep the barrel pointed (up/down). The length of the “barrel” and range of movement will give you how tall the fork(s) must be. If you want, look at what Servo City offers up for pan and tilt mechanisms.
If you want some idea of how it’ll perform, you’ll need to estimate the moments of inertia, one for elevation/tilt and another for azimuth/pan. For your usage you don’t need to be super exact. Wikipedia has a good definition and list of known “easy” moments that you can probably use.
Why estimate the moment of inertia ? It’s the rotational equivalent of mass and if you recall F = MA, then t = Ia where t is the torque applied to the mechanical load, I is the moment of inertia of that load and a is the angular acceleration (deg/sec/sec), should make sense. The moment of inertia will allow you to get a fair guess as to how much torque you’ll need from the motor and any gearing to achieve the point-point timing you want. Your servo motor is going to spend some amount of time accelerating to it’s max (under load) RPM then travel some angular distance (deg) at that speed before it has to begin to slow down (deceleration requires torque too) to settle at the desired position. You need to find the right balance of speed (RPM) and torque applied to the mechanical load to meet your timing requirements.
Once you have some guesstimate of the torques and speeds needed you can choose a motor to fit those needs and then a power supply to run the motors off of.
I only go into this amount of detail as your post seems to indicate you want to learn it. If not you can always follow what someone else has (successfully) done and use that for your starting effort and see what happens.