new robot platform for propeller board

Kris Cardoen

Hi,

I would like to build a new platform for my propeller board.

Ideally using DC motors (not cont. servos) from more power and if possible using Mecanum Wheels.

Does anyone has suggestions, what to buy and where?

I guess I need the following;
- the platform frame (1x)
- DC motors (4 when using Mecanum Wheels)
- Mecanum Wheels (4x)
- Motor controller(s) to intgratie with the propeller board? (do I buy 4 controllers or can I find one controller to handle 4 motors?)
- battery pack + chager

Is this list complete? I'm quite new at this and it is not easy to get started with the correct/best hardware.

Any suggestions/info are welcome!

Kris


Kris

Duane Degn

Kris,

I've been working on and off on a mecanum wheel project.

Go with the Vex mecanum wheels. The Fingertech ones aren't very good (IMO and erco's).

Monitoring four encoders and driving four motors can be a trick. I have some software to do this but my control over the motors isn't a smooth as I'd like. It should be possible to smooth out the control, I just haven't figured it out yet.

The Vex wheels will need to be drilled out to use with the Rover 5 chassis. I'm not completely happy with the Rover 5 but it's hard to beat its price for four motors with encoders.

I'm also not sure I like my motor control solution so far. I recently purchased some different chips (I don't recall the number off the top of my head) that might work better than my first attempt.

I recently purchased a second Rover 5 from a forum member. I thought it might be interesting to watch the Vex mecanum wheels side by side with the Fingertech mecanum wheels.

I've been itching to get back to this project so I might work on it a bit today.

Kris Cardoen

Hi,
Thanks for the feedback. looked at your project ... awsome... i have a long way to go....:thumb:

I was wondering to build my own platform. Starting with the following hardware

- 4 x HB-25 Motor Controller (parallax)
- 4 x 4-Phase / 12 Volt Unipolar Stepper Motor 259 mA (parallax)

I guess I also need a battery pack for power supply to the motors
http://www.batteryspace.com/NiMH-Battery-Pack-Two-12V-1600mAh-NiMH-Battery-10x2/3A-flat-Packs-EDF.aspx

I don't have a lot of expirence so if someone can confirm that these components will work togeather?
It's hard to get started and to find out what is compatible with what.
any help is welcome

Regards,
Kris

Duane Degn

I don't think the HB-25 will drive stepper motors. I also don't think you want stepper motors for this project.

I think a good DC geared motor with an encoder would be the way to go (sorry, I don't have a link, I'll take a look around for an example).

I personally buy NiMH AA batteries and use battery holders to combine them to voltage I want. A forum regular, erco likes the premade packs but I like the ability to replaces a bad cell easily.

I know it's no fun, and I wouldn't take this advice myself when I was younger, but you might want to start out with something less ambitious to gain some experience. You can never have too many robots. You could start with a smaller robot that will follow the larger, mecanum wheel brother, that will be built in the near future.

Duane Degn

I looked around for some gear motors with encoders. I couldn't find any motors with encoders the correct size at Parallax.

Pololu has a nice selection of gear motors with encoders. I'm no expert, but this would be my best guess as a good match with the Vex mecanum wheels. One problem I have with these motors is the relatively short axle. You'd need to drill the Vex mecanum wheels so the set screw was on the motor side of the wheel (I think).

The HB-25 would certainly drive these motors but they might be overkill. It just pains me to think of spending $200 on motor controllers. Pololu doesn't list the current those motors draw so I don't know what kind of controller to recommend. The HB-25s would be up to the task but you might be able to save money by testing the motors and then selecting a controller that will meet its power needs.