Pololu Robotics & Electronics
Menu
My account Comments or questions? About Pololu Contact Ordering information Distributors

Pololu Forum

Tracked robot motor/control questions

Hi All,

Hope someone can point me in the right direction. I am a complete newbie in the robotics world. I have been heavily involved in the RC hobby(planes, cars, heels, quads, etc) for over 21+ years and I have some Arduino experience.

I am embarking on building my first robot. For this project I would the robot be either controlled by RC when active or autonomous via a Raspberry Pi ( I plan on adding some AI to the robot in the future so that is why I want to use the PI).

For the platform I bought a XiaoR Geek Smart Robot Car Tank Chassis Kit. The kit came with geared 12V 370(?) motors which are 160RPM.

I hooked one of the motors up to an RC speed controller with a 2 cell LIPO battery and it does not move the tracks.

Can somebody help me with some recommendations:

  1. Power: I would like to use a LIPO or LION battery to power the robot. How many cells would be recommenced? A 3 cell is in the 12V range

  2. Motors? Is the supplied motors ok…how do I get them to move the tracks (I would like to have proportional speed control if possible)

  3. Speed controller: I see Pololu has speed controllers which accept multiple inputs. I am guess a simple motor controller V2 would be what I am looking for.

Thanks!!!

tbirg

Hello.

We are not too familiar with that robot kit, but using a 3-cell LiPo or Li-ion to power 12V motors seems fine. Keep in mind that you will probably need a step-down regulator to power your Raspberry Pi.

I hope the supplied motors are okay for that kit given that they came with it. You might try testing them without the tracks to make sure they are working, and you could also try connecting them directly to a power supply rather than through your RC speed controller to make sure that is not the problem, but if you keep having trouble with them you might want to contact the manufacturer.

Our G2 Simple Motor Controllers do support various control interfaces, so they might work in your application. They can be configured over USB to accept RC signals, as well as serial or I2C signals from a Raspberry Pi. If you can tell me more about your motors (such as by linking to a datasheet for them or the kit), then I might be able to give a you a more specific recommendation about which model would fit best in your application.

- Patrick

Patrick, thanks.

Going straight to the battery works.

I cannot find a spec sheet for the motors other than to say they are 12V geared 370 brushed motors that turn about 160 RPM.

Here is a link to the vehicle I bought: http://www.xiaorgeek.com/store/robot-accessories/structural-component/multi-color-th-tank-chassis-kit-with-2wd-motors.html

As I said before I would love to get better/stronger motors if possible. The speed controllers only support 2 cell LIPO so that might be the issue.

For the Raspberry PI I am using a 10AMP hobby BEC (battery eliminator circuit) for power.

For me the first step is getting the RC working because that is what I am more familiar with, then move onto the “robot” part of the project.

Ted

We did not make your motors or your RC speed controller, so we cannot offer much support with those. However, presuming you tested with the motors disconnected from the tracks in both cases, if your motors worked with a power supply but did not work with your speed controller, then there must be a problem with the speed controller or how you are using it. I would suggest contacting the manufacturer of that to try to figure out what is going one with the equipment you have before trying anything new.

If you do want to get better characterized motors than what came with your kit, then you might consider our 25D Metal Gearmotors. They look like they might have similar dimensions to the ones in your kit, so they would probably be the easiest option to integrate with the parts you already have. To be safe though, you can compare your motors against the dimension diagram for our 25D motors to make sure they are similar enough.

- Patrick

Thanks for the reply

Last question I have for now. On the G2 motor controller can I use both I2C and RC at the same time? For example if the board does not get a RC signal will it use I2C and when the RC is on will it then use RC control?

Ted

There is not a way to directly do that with the Simple Motor Controllers. You could however send I2C commands to read the RC inputs using “Get variable” and set the motor speeds from your microcontroller based on those values. You can check out the user’s guide for more information about the Simple Motor Controller commands. Alternatively, if you can set up your microcontroller to read an RC signal you could just connect your signal there and then do everything from your microcontroller.

- Patrick