Model Boat Mayhem
Technical, Techniques, Hints, and Tips => DC Motors (Brushed) and Speed Controllers => Topic started by: ZZ56 on May 22, 2009, 11:46:32 pm
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Hi all,
Was looking for a 12v ESC and i found a couple on a website for a Canadian store, which means it should be the cheapest route to get one.
There's the old Dumas 12 volter, which is a mechanical rheostat. The cheapest option, but it doesn't have a BEC, and it's still 70 dollars. I'm leery of paying that much for a rheostat, considering it might be possible to pluck one from a broken appliance for nothing. On the plus side, I heard that electronic controls give off noises that mechanical ones dont.
There is this one (http://www.greathobbies.com/productinfo/?prod_id=GRA2736) from Graupner, but damned if i can find any more info on it. Since 12v is the highest capacity listed, im worried it would be dangerous at full throttle.
The most expensive option is this unit (http://www.greathobbies.com/productinfo/?prod_id=AST208D) from Astro Flight, which should be more than enough, but if the Graupner or Dumas units would work okay, I'd prefer to pinch pennies.
Personally i know NOTHING about ESCs, and i just want one that doesn't require separate cards or wiring to program, and that will work with a 12v system providing forward and reverse.
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Look on ebay or contact FLJ (Dave) at action on here
Now your sorted
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What type of boat and motor do you need the Speed Controller for?
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Scale boat, quite large, with a 12v brushed motor.
Not quite sure where the motor is from, originally... it has TWO sets of wires coming out of it. But, it's got lots of torque, is quiet, and not to high on the RPMs
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If the rheostat is an exact match to the motor, it will work just fine, but will reduce run time. If it is not an exact match, it will perform as a switch. As the motor is an unknown type, it becomes anybody's guess.
There is the chance of a whine from PWM ESCs (most of them) if the pulse rate is in the audible range, but the actual level of the sound depends on the individual motor, its mounting, hull construction and the operating method of the ESC.
4 wires? Either the brushes have duplicate wiring (can't think why) or it is a field wound motor. In a "normal" motor, power is fed to the brushes which pass power to the armature via the commutator. This acts against the permanent magnet and causes the motor to turn. In a field wound motor, there is no permanent magnet, this function is done using a coil. This has the effect of only allowing the motor to turn in one direction unless some other action is taken.
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(http://img.photobucket.com/albums/v323/DestructorBot/IMG_1257.jpg)
Changing the polarity changes the direction of rotation, so it doesn't sound like a field-wound motor. In fact, before i trimmed them back i tried attaching the front wires to the battery... nothing happened. Maybe they were for some sort of electronic measuring device hookup?
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Yes the square thingy on the case by the pulley could be some sort of counting sensor or part of a governor arrangement. In the days before stepper motors were common, a sensor would be used to keep track of what the motor had been up to. Early non-graphic printers spring to mind, both paper transport and head drive but no doubt there were plenty of other applications.