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Author Topic: Gun turret rotation - servo or stepper motor?  (Read 13340 times)

Norman Castle

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Re: Gun turret rotation - servo or stepper motor?
« Reply #50 on: January 13, 2016, 03:20:30 PM »

I've quickly done a video on a gun turret project I'm working on, so you can see how slowly and smoothly a stepper can operate. I've made the speed of traverse proportional to joystick displacement which may or may not be a good idea?

Now working on a second channel to "fire" the gun - storing the "bang" as a sound sample in the Arduino

Crikey!  That's well impressive.  And I had no idea you can store a sound sample on an Arduino ...
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plastic

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Re: Gun turret rotation - servo or stepper motor?
« Reply #51 on: January 13, 2016, 05:53:25 PM »

Clever - but if you are going to synchronise the turrets to all point at one target, how do you designate the coordinates of the fixed target point to a moving boat?

Could you not get the same effect easier in the old analogue way that linear-tracker record players used of LEDs down the bore and locking on when the correct colour/pattern is lined up?

You could just chuck a target buoy into the water and let the guns find it optically and they would stay locked on no matter what the boat did. You could use an actual designator to find it that then enables the guns when a 'lock' is found.
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afb

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Re: Gun turret rotation - servo or stepper motor?
« Reply #52 on: January 13, 2016, 05:57:42 PM »

Norman - there's 32K of program space on the Uno/Nano (328 based ones) so if your control program isn't too large you could have say 24k of memory free in which to store sound samples - that's 3 secs of audio at 8K sampling rate. Use the PROGMEM statement which is part of the "pgmspace.h" library to store data in the program memory. Formatting the sound data before you put it in there and then playing it out again is not trivial however, if you're already struggling to move a stepper!
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dreadnought72

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Re: Gun turret rotation - servo or stepper motor?
« Reply #53 on: January 13, 2016, 06:53:52 PM »

Clever - but if you are going to synchronise the turrets to all point at one target, how do you designate the coordinates of the fixed target point to a moving boat?

Thinking of typical ranges of the time as 8000yds and up, at the scale I'm working at, the minimum distance to target would be about 110yds. All turrets would effectively be parallel.

A scaled 20 knots is about 'walking pace', say 10 feet per second. At 110 yards the change in angle of a target, at maximum, is only a degree a second or so. When on parallel/near-parallel courses (like most of the actions in WW1) the angular change is minimal.

To effect a turret rotation as the target changes bearing is automatic during a turn by the turret-carrying vessel, and would require a simple 'new target heading' and 'set' transmission in the system I'm developing.

IDEALLY, all prospective targets (!) should mount an IR-LED on their masts. There are chips available that can read signals from such LEDs. The work of scanning the horizon for a target wouldn't be impossible using Arduinos/other processors. ...Which, I suppose, would be a game changer for those who are determined to sink boats with gas-powered bbs.

Andy
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plastic

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Re: Gun turret rotation - servo or stepper motor?
« Reply #54 on: January 13, 2016, 07:08:19 PM »

Thinking of typical ranges of the time as 8000yds and up, at the scale I'm working at, the minimum distance to target would be about 110yds. All turrets would effectively be parallel.

A scaled 20 knots is about 'walking pace', say 10 feet per second. At 110 yards the change in angle of a target, at maximum, is only a degree a second or so. When on parallel/near-parallel courses (like most of the actions in WW1) the angular change is minimal.

To effect a turret rotation as the target changes bearing is automatic during a turn by the turret-carrying vessel, and would require a simple 'new target heading' and 'set' transmission in the system I'm developing.

IDEALLY, all prospective targets (!) should mount an IR-LED on their masts. There are chips available that can read signals from such LEDs. The work of scanning the horizon for a target wouldn't be impossible using Arduinos/other processors. ...Which, I suppose, would be a game changer for those who are determined to sink boats with gas-powered bbs.

Andy

Very easy to do with analogue circuits - fit an IR LED that flashes a pulse train on a rotating 'designator' on the warship and retro-reflectors on the target buoy/boat and when the pulse train is detected by the turrets L & R detectors, they turn until the boresight detector picks up the signal which means the gun is trained.
Duplicate circuits in each turret and they'll work independently as a team to stay trained on target no matter where the boat is in relation to the target.
This can be done with a couple of op-amps like the old record players tone-arm.

If all you are going to do is turn the turrets to 90 deg, why bother with all your complication? The old Lindberg Blue Devil Destroyer mechanism could do that.
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dreadnought72

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Re: Gun turret rotation - servo or stepper motor?
« Reply #55 on: January 13, 2016, 07:39:56 PM »

If all you are going to do is turn the turrets to 90 deg, why bother with all your complication? The old Lindberg Blue Devil Destroyer mechanism could do that.

? That's not at all what I'm attempting to do.

Andy
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