This page (revision-6) was last changed on 2021-11-16 22:18 by Murray Altheim

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Motors
Motors

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At line 5 removed 6 lines
%%warning
__Note:__ Stalling or overloading gearmotors can greatly decrease their lifetimes and even result in immediate damage. The recommended upper limit for instantaneous torque is 2.5 kg-cm (35 oz-in) for the 380:1 and 1000:1 gearboxes, and 2 kg-cm (25 oz-in) for all the other gear ratios; we strongly advise keeping applied loads well under this limit. Stalls can also result in rapid (potentially on the order of seconds) thermal damage to the motor windings and brushes, especially for the versions that use high-power (HP and HPCB) motors; a general
recommendation for brushed DC motor operation is 25% or less of the stall current. — ''source:  [Pololu|https://www.pololu.com/product/997]''
%%
So... if your motor controller permits sensing of motor current it sounds like a good idea to pay attention
to it. Your motor's life could depend on it.
At line 12 removed 30 lines
!! Choice of Motors
The choice of motors will depend entirely on the __scale__ of the robots you might build. If you're fairly serious about robotics (i.e., you don't just want a remote-controlled toy), you'll probably want to choose motors that have Hall effect motor encoders either already attached or as an option. This is to permit you to precisely measure how far each motor has travelled, its velocity, and likewise perform odometry. This is absolutely necessary for autonomous navigation: if the robot can't travel in a straight line or tell where it is in 2D space it can't navigate, it just runs around avoiding obstacles (hopefully).
On the smaller end of high quality motors with encoders you can find lots on the Pololu website as "micro metal gearmotors" (AKA N20), with encoders. These come in a variety of power ratings and a large number of gear ratios. Pololu also sell a variety of larger motors, as well as motor drivers and motor controllers.
If you're looking at larger robots you can find a variety of motors with encoders on the ServoCity (Imperial measurement) and goBILDA (metric) web sites. These come in 22mm, 25mm, on up to larger motors. Of course, the larger the motor the higher torque, but also the often significantly higher power requirements (and lower battery life, therefore requiring larger and heavier and more expensive batteries).
If you're planning on having your robot operate outdoors or on uneven terrain, you'll want ball bearings on the output shafts. Plain bearings won't last long when bouncing over rocks.
So the first thing really to do is determine the scale of your first robot, then select a motor suitable for that scale.
!! Pololu Micro Gear Motors
These tiny brushed DC gearmotors are available in a wide range of gear ratios—from 5:1 up to 1000:1—and with five different motors: high-power 6 V and 12 V motors with long-life carbon brushes (HPCB), and high-power
(HP), medium power (MP), and low power (LP) 6 V motors with shorter-life precious metal brushes. The 6 V and 12 V HPCB motors offer the same performance at their respective nominal voltages, just with the 12 V motor drawing half the current of the 6 V motor. The 6 V HPCB and 6 V HP motors are identical except for their brushes, which only affect the lifetime of the motor.
!! OSEPP Motor
This is the motor that comes with the OSEPP Tank Kit. You can buy motor kits that come with an anodised aluminium wheel, a silicon tire. A Hall Effect [motor encoder] kit is available separately.
* Voltage: 9v DC
* Length: 52mm
* Diameter: 25mm
* Rated Torque (Kgf.cm): 1.5
* RPM: 8500
This page (revision-6) was last changed on 2021-11-16 22:18 by Murray AltheimTop