Hey folks! I've been using standard-sized sail winch servos for years for turret rotation. unfortunately those are extremely hard to find and expensive nowadays, so I'm starting to look for alternatives. After doing some research, stepper motors (with suitable controllers) have emerged as a possible substitute. Has anybody used these before? Any concerns about water immersion? Any other concerns I should be aware about?
TBH I have thought about using them for all sorts of things. Steppers draw a lot of amps, so you’re going to have to deal with that. You’d want something like a NEMA 8 but for the $20 price, you could get a full rotation servo. https://www.pololu.com/category/87/stepper-motors Do you need a lot of torque for your rotation set up? Or is it geared down enough to use a smaller servo View: https://www.amazon.com/dp/B079FRHBTR/ref=cm_sw_r_cp_api_glt_fabc_Y5695YCHPQ9SAQ6F5W7W
Just finished an initial test with the smallest stepper that Pololu sells, one of their TIC stepper motor controllers, and one of my prototype predread cannons. Even this tiny motor, at rated torque, was easily able to spin the cannon around quickly and precisely. I am confident that a similar assembly could be used to provide position control for almost any size cannon, unlike the common velocity-control systems currently in use. Setup was extremely simple with a USB-micro cable. I told the stepper controller what the radio signal for center and full deflection in either direction were, then told it how many steps to move for full deflection. After less than a minute of trial and error, I had the turret dialed in to 270 degrees rotation in under two seconds. It isn't *quite* as plug-and-play as a servo, but it is very close. Most importantly, it provides the multi-turn positional control that I need for effective turret rotation. Power draw is only a few hundred milli-amps, and if I get rammed by an Iowa or Yamato then it'll just slip poles with no harmful effects. Looking inside the motor, it looks fairly water resistant. The motor windings are well-sealed, and the rotor is a single solid piece. My only concern is general corrosion due to water. It has a pair of ball bearings, one at either end, that will probably need to be oiled after every battle day, and the interior may also be susceptible to long-term general corrosion. At some point I may look into drilling oil ports for easy flushing after a sink. The stepper motor controller is a solid-state circuitboard, easily waterproofed with skotchkote or similar surface sealant. It's worth noting that you'd need both a stepper motor and TIC controller for each set of turrets you're trying to control, so it's not actually $24 per motor. It's actually a little over $65 when you include the controller, which is still half the price of the multi-turn servos currently on the market. The other option is to roll your own circuitboard. That's a little beyond my expertise at this time, but if there is somebody who knows circuitboard design, feel free to take a stab at it. My ideal solution is a custom circuitboard like the BC cruiser/battleship boards or the vac-u-gearing boards, that contains everything you need for pump, drive, turret rotation, and firing.
Honestly, once you are into steppers, if you are willing and able to write firmware for them, there are a ton of control boards for them. 8 bit boards with 5 driver's for30 bucks or so. Hard part becomes firmware writing. Nick might have some ideas as well.
https://github.com/bolderflight/sbus If you are using frsky , the above would be a.good start. Arduino plus standard inexpensive drivers, and only one connection to rx for as many channels as you would ever need.
Fantastic info. I never knew there was a stepper controller that would take hobby RC signal. I could see a lot of uses. Thanks for sharing!
