Author Topic: motors  (Read 2673 times)

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Offline BuddingContraptionistTopic starter

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motors
« on: November 20, 2008, 06:36:51 PM »
i think i want to make a wheeled contraption... where can i buy good robot motors?  I found this motor at sparkfun, which nicely matches this gearbox.  But that's the only motor and the only gearbox they sell.  Where is a good place for motors?  (and on a semi-related where-do-i-find-this-stuff note, anyone know where i can find one of these JST connectors for the sharp IR range finder? i got a rangefinder but forgot to get that cable and i dont want to order just one thing all the way from canada)
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Offline Trumpkin

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Re: motors
« Reply #1 on: November 20, 2008, 07:35:31 PM »
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Offline Webbot

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Re: motors
« Reply #2 on: November 20, 2008, 08:52:45 PM »
Quote from: BuddingContraptionist on November 20, 2008, 06:36:51 PM
(and on a semi-related where-do-i-find-this-stuff note, anyone know where i can find one of these JST connectors for the sharp IR range finder? i got a rangefinder but forgot to get that cable and i dont want to order just one thing all the way from canada)
See other forum posts re connecting directly to the sensor without using a connector
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Offline BuddingContraptionistTopic starter

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Re: motors
« Reply #3 on: November 23, 2008, 07:11:51 PM »
is it bad for a motor to run it at a lower voltage than it's rated at?  like if i get one that's 12v, but use a 9v battery to run it?
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paulstreats

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Re: motors
« Reply #4 on: November 24, 2008, 06:15:54 AM »
solarbotics sell lots of different motors, many with gearheads already attached
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Offline ArcMan

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Re: motors
« Reply #5 on: November 24, 2008, 10:19:32 AM »
Quote from: BuddingContraptionist on November 23, 2008, 07:11:51 PM
is it bad for a motor to run it at a lower voltage than it's rated at?  like if i get one that's 12v, but use a 9v battery to run it?

No problem for a DC motor.  Reducing and increasing the DC voltage is exactly how speed control is attained.  So running a 12V motor at 9V just means that it will run slower with less torque.
Given that, let me say that running a motor with a 9V battery will drain that battery very quickly unless that motor is really small.

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Offline Admin

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Re: motors
« Reply #6 on: November 28, 2008, 01:01:12 AM »
Running a motor at a lower voltage won't break anything, but as ArcMan said, it will have lower torque/speed.

Quote
Reducing and increasing the DC voltage is exactly how speed control is attained.  So running a 12V motor at 9V just means that it will run slower with less torque.
Given that, let me say that running a motor with a 9V battery will drain that battery very quickly unless that motor is really small.
A motor is most efficient at the rated voltage - meaning a higher torque/joule ratio. So less wasted battery energy, basically.

But the proper way to control motor speed is through PWM, which is like turning the motor on/off really fast so that it reaches some medium speed.
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