ELECINF344/381

Interactive web site of Télécom ParisTech's ELECINF344/ELECINF381 Robotics and Embedded Systems classes (a.k.a. ROSE, 2012 session).

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Motors motors motors…

We talked about motors and encoders with the teachers and it turns out we can spend a little bit more on the encoders. Also, they said (if I got it right) that doing our own optical encoders could be complicated to calibrate. They mentioned we could take the chassis out and use the board as chassis. Well, all that said, today I looked for motors + encoder + wheels again, and set up some possible “kits”.

Option 1:

Motor 10 € (does not need a support)
http://www.robotshop.com/eu/tamiya-twin-motor-gearbox.html
Big wheels 6 € a pair
http://www.robotshop.com/eu/tamiya-narrow-tire-set.html

Or smaller wheels, 3 € a pair
http://www.robotshop.com/eu/tamiya-off-road-tires.html
Encoder 10 € each, 16 points per turn.
http://www.robotshop.com/eu/cytron-simple-rotary-encoder-kit.html

Total 36 € (with the big wheels)

 

Option 2:

Motor with encoder 20 € each. There’s no information on the encoder’s precision.
http://www.lextronic.fr/P5448-moteur-reducteur-avec-encodeur.html
Compatible pair of wheels 11 €
http://www.lextronic.fr/P5450-paire-de-roue-pour-moteur-65-mm.html
motor support 5 € (needed unless we paste the motor onto the board )
http://www.lextronic.fr/P5449-jeu-de-2-supports-pour-moteurs.html

Total 56 €

 

Option 3 (expensive):

wheels+encoders+motor support 42€. encoder has 48 points per turn
http://www.lextronic.fr/P23462-pack-roues–encodeurs–supports.html
motor 12 € each
http://www.lextronic.fr/P4234-moteur-reducteur-miniature-pololu-993.html

Total 66€

There is also the option of using mechanical encoders, they are like a potentiometer that turns without ending. They are quite cheap, about 3 € each, but we need to make a gear system to attach it to the motor axis.

I got 2 examples:
http://www.robotshop.com/eu/parallax-incremental-rotary-encoder.html
http://www.robotshop.com/eu/5v-mechanical-quadrature-encoder.html
These 2 have 32 points per turn, it’s more precise than many optical encoders available. On the other hand, their specifications mention they have a life-cycle of only 100.000 turns, which seemed to us a little low considering motor speed.

We would need a motor with a rear shaft to attach the potentiometer, like one of these:
motor 20€
http://www.robotshop.com/eu/lyn-ghm-16.html
motor 15€
http://www.robotshop.com/eu/solutions-cubed-m12v200-motor-rear-shaft.html
This option considering a 6 € wheel pair would cost around 42 €, and we don’t know much about doing the gears to attach the potentiometer.

I personally like the cheap option 1, but the encoder’s resolution might be disappointing (it’s there where the option 3 is better, and the 2 maybe). Also I’m not so sure of the way we’re going to mount it on the board, since the sensor needs to fit around the encoding wheel. I imagine we can order a board with holes for the wheels and encoding wheels, and the sensor can stay on the board on the side of the encoding wheel. What do you think about it?

Possibly related posts:

  1. Trying to choose motors…
  2. Tutobot – Components

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