Recommendations for dc motors?

AwesomeCronkAwesomeCronk Posts: 976
edited 2020-03-28 - 21:59:25 in Accessories
I want to build a small bot that would be able to really go quick. I am looking in the ballpark of 200RPM dc motors, likely two-wheel-drive. Would use a prop mini and L298N to drive them. I would likely use four AA batteries, just like the BOE-Bot does.

I have looked at these motors, which look really good so far as strength, but I cannot find them on amazon for less than $7.55 and I really would like to buy from there. Also, the little yellow kits for the famous DIY Ardy bluetooth smart cars are $11 for four motors. So I ask here: Should I buy the all metal ones from Ebay or buy the yellow plastic ones from Amazon?

Comments

  • Be careful with those GA12-N20 motors. I bought some which didn’t specify the shaft dia. They arrived as 1.9mm which is too small to put on my 3D printed wheels. The one you linked quotes 3mm dia but I thought I needed 3.5mm. Anyway I just ordered another pair with 3mm. I have printed a SMARS robot (smart car with tracks).

    Also there are various voltages 3V, 6V and 12V? and speeds - I ordered 6V 150RPM but I’m just guessing here. One of the better suppliers has a complete matrix of these selections. Alicennnn (forget the number) are a respectable eBay supplier but I can’t recall if my next motors are coming from them.
  • Duane DegnDuane Degn Posts: 10,263
    edited 2020-04-02 - 12:54:09
    If you want the robot to navigate, I strongly suggest getting motors with quadrature encoders. In my opinion, you really need encoders for a "proper" robot. Here's a one I found on Amazon. (I haven't used these exact motors myself.)

    AmazonMotorSmallerB.jpg
    Would use a prop mini and L298N to drive them.

    The L298N robs a lot of the power from your battery but they're hard to pass up since they're so inexpensive.
    I made a video showing how to hook up a L298N to a Propeller. Unless you already know what you're doing, you might want to watch the video.

    As a robot's battery drains, the power delivered to the motors change over time. This makes it really hard to get the robot to drive in a predictable way without using quadrature encoders.

    Regulating the voltage delivered to the motors in a less refined way of attempting to get predictable behavior from a robot. While attempting to get my Cheap Bot to drive in a figure 8, I found I couldn't make it work until I regulated the power to continuous rotation servos. Using motors with quadrature encoders would have made regulating the power unnecessary.

    The only set of motors with quadrature encoders I could find in the Parallax store are these expensive but beautiful monsters.

    Edit: Shrunk motor photo.
    458 x 382 - 44K
  • WhitWhit Posts: 4,138
    edited 2020-05-08 - 03:03:23
    Duane Degn wrote: »
    The only set of motors with quadrature encoders I could find in the Parallax store are these expensive but beautiful monsters.

    They are fantastic too. Worth every penny! I have an Arlo, and a custom build mini-Arlo that I calll m-Arlo with the original 12 volt motors.

    @AwesomeCronk - you might want to contact @erco - he has lots of experience with different motor types. Some of those cheap yellow motors are really bad.
  • That’s kinda what I figured with the yellow motors. I’m kinda shooting for a bot about the size of the BOE-Bot, so I won’t be going for the Arlo motors. I think I will go for the motor Duane posted a picture of.
  • Duane,
    That is an awesome motor. To Cronk, check with Erco on motor drivers. he found some on Ebay that emulated a servo and was cheaper than lm298 and did not rob you of power to to youmoters.
    Jim
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