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Large DC Motors


 For purposes of this website Large DC Motors refer to DC motors that run on more than 12 volts. Power for motors in this classification would typically be powered by 12V volt batteries of the type you might find in motorized scooters, automobiles and "power wheel" type toys.

When using larger DC motors you need to be much more aware of concepts like amperage. Larger motors can use a large amount of current so wire sizes and switch ratings become much more important. Under-sizing wire or switches to a larger motor can result in several types of problems: among those being overheating wire and melting insulation, fire hazard and risk of shorts.

Usually, these motors must be powered by some type of commercial 12v Battery such as the one in this image. Most wall transformers do not put out sufficient current to power this type of motor. Make sure that the battery you choose is capable of delivering the amperage required by your motor. The battery in the image is a 7.5Ah (ampere-hour) battery. Roughly, the ampere-hour rating describes the amperage output of the battery. Thus, this battery can output 7.5 amps for one hour or 15 amps for 1/2 an hour. Since DI performances are only 8 minutes long this battery (if fully charged) would be more than sufficient to provide power during a performance to a motor requiring a maximum of 15 amps of current. (It is highly unlikely that you would have a situation where a motor was using its maximum current rating for the duration of a performance).

Most commercial application motors will have plates on them that describe the voltage and amperage required for the motor to run. There may be two amperage ratings. One rating for no-load and one rating that is either a fully loaded or a motor stall rating. A motor that uses only 2 amps of current with no load may use up to 12 amps of current when the motor is put into a stall condition. A stall condition is when power is still applied to the motor but the motor is prevented from turning. Your circuits should be designed to handle the stall rating of the motor. You should also include some type of safety or limit switch to shut off the motor should the motor get into a stall condition.

Car Windshield Wiper motors are a good source of relatively powerful inexpensive DC motors. These typically operate on 12 volts and have enough torque to accomplish many types of tasks. In some cases you may find windshield wiper motors at a junk yard. You can also purchase them on ebay.

Picture: Windshield Wiper motor. Video: 12 Volt windshield wiper motor operating. This motor was purchased on ebay for $3.00 (not including shipping). The motor came with the wiper control arms still attached. These arms could be used to create some type of reciprocating motion.

I found an interesting windshield wiper motor at Allectronics.com When wired correctly this windshield wiper motor will always stop in the same place. When power is applied to it briefly it will make exactly one revolution and stop. Video: Allelectronics windshield wiper motor.

Other sources of more powerful DC motors would include: Automobile automatic window motors, motors from "power wheels" toys, and motors from some small appliances.